Indicates that the method completed successfully. This reply code is reserved for future use - the current protocol design does not use positive confirmation and reply codes are sent only in case of an error. The client asked for a specific message that is no longer available. The message was delivered to another client, or was purged from the queue for some other reason. The client attempted to transfer content larger than the server could accept at the present time. The client may retry at a later time. When the exchange cannot route the result of a .Publish, most likely due to an invalid routing key. Only when the mandatory flag is set. When the exchange cannot deliver to a consumer when the immediate flag is set. As a result of pending data on the queue or the absence of any consumers of the queue. An operator intervened to close the connection for some reason. The client may retry at some later date. The client tried to work with an unknown virtual host. The client attempted to work with a server entity to which it has no access due to security settings. The client attempted to work with a server entity that does not exist. The client attempted to work with a server entity to which it has no access because another client is working with it. The client requested a method that was not allowed because some precondition failed. The client sent a malformed frame that the server could not decode. This strongly implies a programming error in the client. The client sent a frame that contained illegal values for one or more fields. This strongly implies a programming error in the client. The client sent an invalid sequence of frames, attempting to perform an operation that was considered invalid by the server. This usually implies a programming error in the client. The client attempted to work with a channel that had not been correctly opened. This most likely indicates a fault in the client layer. The server could not complete the method because it lacked sufficient resources. This may be due to the client creating too many of some type of entity. The client tried to work with some entity in a manner that is prohibited by the server, due to security settings or by some other criteria. The client tried to use functionality that is not implemented in the server. The server could not complete the method because of an internal error. The server may require intervention by an operator in order to resume normal operations. An access ticket granted by the server for a certain set of access rights within a specific realm. Access tickets are valid within the channel where they were created, and expire when the channel closes. Identifier for the consumer, valid within the current connection. The server-assigned and channel-specific delivery tag The delivery tag is valid only within the channel from which the message was received. I.e. a client MUST NOT receive a message on one channel and then acknowledge it on another. The server MUST NOT use a zero value for delivery tags. Zero is reserved for client use, meaning "all messages so far received". The exchange name is a client-selected string that identifies the exchange for publish methods. Exchange names may consist of any mixture of digits, letters, and underscores. Exchange names are scoped by the virtual host. Specifies the list of equivalent or alternative hosts that the server knows about, which will normally include the current server itself. Clients can cache this information and use it when reconnecting to a server after a failure. This field may be empty. If this field is set the server does not expect acknowledgements for messages. That is, when a message is delivered to the client the server automatically and silently acknowledges it on behalf of the client. This functionality increases performance but at the cost of reliability. Messages can get lost if a client dies before it can deliver them to the application. If the no-local field is set the server will not send messages to the connection that published them. Must start with a slash "/" and continue with path names separated by slashes. A path name consists of any combination of at least one of [A-Za-z0-9] plus zero or more of [.-_+!=:]. This string provides a set of peer properties, used for identification, debugging, and general information. The queue name identifies the queue within the vhost. Queue names may consist of any mixture of digits, letters, and underscores. This indicates that the message has been previously delivered to this or another client. The server SHOULD try to signal redelivered messages when it can. When redelivering a message that was not successfully acknowledged, the server SHOULD deliver it to the original client if possible. Create a shared queue and publish a message to the queue. Consume the message using explicit acknowledgements, but do not acknowledge the message. Close the connection, reconnect, and consume from the queue again. The message should arrive with the redelivered flag set. The client MUST NOT rely on the redelivered field but should take it as a hint that the message may already have been processed. A fully robust client must be able to track duplicate received messages on non-transacted, and locally-transacted channels. The reply code. The AMQ reply codes are defined as constants at the start of this formal specification. The localised reply text. This text can be logged as an aid to resolving issues. Specifies the destination to which the message is to be transferred. The destination can be empty, meaning the default exchange or consumer. The reject code must be one of 0 (generic) or 1 (immediate delivery was attempted but failed). Used for authentication, replay prevention, and encrypted bodies. The connection class provides methods for a client to establish a network connection to a server, and for both peers to operate the connection thereafter. connection = open-connection *use-connection close-connection open-connection = C:protocol-header S:START C:START-OK *challenge S:TUNE C:TUNE-OK C:OPEN S:OPEN-OK | S:REDIRECT challenge = S:SECURE C:SECURE-OK use-connection = *channel close-connection = C:CLOSE S:CLOSE-OK / S:CLOSE C:CLOSE-OK This method starts the connection negotiation process by telling the client the protocol version that the server proposes, along with a list of security mechanisms which the client can use for authentication. If the server cannot support the protocol specified in the protocol header, it MUST close the socket connection without sending any response method. The client sends a protocol header containing an invalid protocol name. The server must respond by closing the connection. The server MUST provide a protocol version that is lower than or equal to that requested by the client in the protocol header. The client requests a protocol version that is higher than any valid implementation, e.g. 9.0. The server must respond with a current protocol version, e.g. 1.0. If the client cannot handle the protocol version suggested by the server it MUST close the socket connection. The server sends a protocol version that is lower than any valid implementation, e.g. 0.1. The client must respond by closing the connection. The protocol version, major component, as transmitted in the AMQP protocol header. This, combined with the protocol minor component fully describe the protocol version, which is written in the format major-minor. Hence, with major=1, minor=3, the protocol version would be "1-3". The protocol version, minor component, as transmitted in the AMQP protocol header. This, combined with the protocol major component fully describe the protocol version, which is written in the format major-minor. Hence, with major=1, minor=3, the protocol version would be "1-3". The properties SHOULD contain at least these fields: "host", specifying the server host name or address, "product", giving the name of the server product, "version", giving the name of the server version, "platform", giving the name of the operating system, "copyright", if appropriate, and "information", giving other general information. Client connects to server and inspects the server properties. It checks for the presence of the required fields. A list of the security mechanisms that the server supports, delimited by spaces. A list of the message locales that the server supports, delimited by spaces. The locale defines the language in which the server will send reply texts. The server MUST support at least the en_US locale. Client connects to server and inspects the locales field. It checks for the presence of the required locale(s). This method selects a SASL security mechanism. The properties SHOULD contain at least these fields: "product", giving the name of the client product, "version", giving the name of the client version, "platform", giving the name of the operating system, "copyright", if appropriate, and "information", giving other general information. A single security mechanisms selected by the client, which must be one of those specified by the server. The client SHOULD authenticate using the highest-level security profile it can handle from the list provided by the server. If the mechanism field does not contain one of the security mechanisms proposed by the server in the Start method, the server MUST close the connection without sending any further data. Client connects to server and sends an invalid security mechanism. The server must respond by closing the connection (a socket close, with no connection close negotiation). A block of opaque data passed to the security mechanism. The contents of this data are defined by the SASL security mechanism. A single message locale selected by the client, which must be one of those specified by the server. The SASL protocol works by exchanging challenges and responses until both peers have received sufficient information to authenticate each other. This method challenges the client to provide more information. Challenge information, a block of opaque binary data passed to the security mechanism. This method attempts to authenticate, passing a block of SASL data for the security mechanism at the server side. A block of opaque data passed to the security mechanism. The contents of this data are defined by the SASL security mechanism. This method proposes a set of connection configuration values to the client. The client can accept and/or adjust these. The maximum total number of channels that the server allows per connection. Zero means that the server does not impose a fixed limit, but the number of allowed channels may be limited by available server resources. The largest frame size that the server proposes for the connection. The client can negotiate a lower value. Zero means that the server does not impose any specific limit but may reject very large frames if it cannot allocate resources for them. Until the frame-max has been negotiated, both peers MUST accept frames of up to frame-min-size octets large, and the minimum negotiated value for frame-max is also frame-min-size. Client connects to server and sends a large properties field, creating a frame of frame-min-size octets. The server must accept this frame. The delay, in seconds, of the connection heartbeat that the server wants. Zero means the server does not want a heartbeat. This method sends the client's connection tuning parameters to the server. Certain fields are negotiated, others provide capability information. The maximum total number of channels that the client will use per connection. If the client specifies a channel max that is higher than the value provided by the server, the server MUST close the connection without attempting a negotiated close. The server may report the error in some fashion to assist implementors. The largest frame size that the client and server will use for the connection. Zero means that the client does not impose any specific limit but may reject very large frames if it cannot allocate resources for them. Note that the frame-max limit applies principally to content frames, where large contents can be broken into frames of arbitrary size. Until the frame-max has been negotiated, both peers MUST accept frames of up to frame-min-size octets large, and the minimum negotiated value for frame-max is also frame-min-size. If the client specifies a frame max that is higher than the value provided by the server, the server MUST close the connection without attempting a negotiated close. The server may report the error in some fashion to assist implementors. The delay, in seconds, of the connection heartbeat that the client wants. Zero means the client does not want a heartbeat. This method opens a connection to a virtual host, which is a collection of resources, and acts to separate multiple application domains within a server. The server may apply arbitrary limits per virtual host, such as the number of each type of entity that may be used, per connection and/or in total. The name of the virtual host to work with. If the server supports multiple virtual hosts, it MUST enforce a full separation of exchanges, queues, and all associated entities per virtual host. An application, connected to a specific virtual host, MUST NOT be able to access resources of another virtual host. The server SHOULD verify that the client has permission to access the specified virtual host. The client can specify zero or more capability names, delimited by spaces. The server can use this string to how to process the client's connection request. In a configuration with multiple collaborating servers, the server may respond to a Connection.Open method with a Connection.Redirect. The insist option tells the server that the client is insisting on a connection to the specified server. When the client uses the insist option, the server MUST NOT respond with a Connection.Redirect method. If it cannot accept the client's connection request it should respond by closing the connection with a suitable reply code. This method signals to the client that the connection is ready for use. This method redirects the client to another server, based on the requested virtual host and/or capabilities. When getting the Connection.Redirect method, the client SHOULD reconnect to the host specified, and if that host is not present, to any of the hosts specified in the known-hosts list. Specifies the server to connect to. This is an IP address or a DNS name, optionally followed by a colon and a port number. If no port number is specified, the client should use the default port number for the protocol. This method indicates that the sender wants to close the connection. This may be due to internal conditions (e.g. a forced shut-down) or due to an error handling a specific method, i.e. an exception. When a close is due to an exception, the sender provides the class and method id of the method which caused the exception. After sending this method any received method except the Close-OK method MUST be discarded. When the close is provoked by a method exception, this is the class of the method. When the close is provoked by a method exception, this is the ID of the method. This method confirms a Connection.Close method and tells the recipient that it is safe to release resources for the connection and close the socket. A peer that detects a socket closure without having received a Close-Ok handshake method SHOULD log the error. The channel class provides methods for a client to establish a channel to a server and for both peers to operate the channel thereafter. channel = open-channel *use-channel close-channel open-channel = C:OPEN S:OPEN-OK / C:RESUME S:OK use-channel = C:FLOW S:FLOW-OK / S:FLOW C:FLOW-OK / S:PING C:OK / C:PONG S:OK / C:PING S:OK / S:PONG C:OK / functional-class close-channel = C:CLOSE S:CLOSE-OK / S:CLOSE C:CLOSE-OK This method opens a channel to the server. The client MUST NOT use this method on an already-opened channel. Client opens a channel and then reopens the same channel. Configures out-of-band transfers on this channel. The syntax and meaning of this field will be formally defined at a later date. This method signals to the client that the channel is ready for use. This method asks the peer to pause or restart the flow of content data. This is a simple flow-control mechanism that a peer can use to avoid overflowing its queues or otherwise finding itself receiving more messages than it can process. Note that this method is not intended for window control. The peer that receives a disable flow method should finish sending the current content frame, if any, then pause. When a new channel is opened, it is active (flow is active). Some applications assume that channels are inactive until started. To emulate this behaviour a client MAY open the channel, then pause it. When sending content frames, a peer SHOULD monitor the channel for incoming methods and respond to a Channel.Flow as rapidly as possible. A peer MAY use the Channel.Flow method to throttle incoming content data for internal reasons, for example, when exchanging data over a slower connection. The peer that requests a Channel.Flow method MAY disconnect and/or ban a peer that does not respect the request. This is to prevent badly-behaved clients from overwhelming a broker. If 1, the peer starts sending content frames. If 0, the peer stops sending content frames. Confirms to the peer that a flow command was received and processed. Confirms the setting of the processed flow method: 1 means the peer will start sending or continue to send content frames; 0 means it will not. This method indicates that the sender wants to close the channel. This may be due to internal conditions (e.g. a forced shut-down) or due to an error handling a specific method, i.e. an exception. When a close is due to an exception, the sender provides the class and method id of the method which caused the exception. After sending this method any received method except the Close-OK method MUST be discarded. When the close is provoked by a method exception, this is the class of the method. When the close is provoked by a method exception, this is the ID of the method. This method confirms a Channel.Close method and tells the recipient that it is safe to release resources for the channel. A peer that detects a socket closure without having received a Channel.Close-Ok handshake method SHOULD log the error. This method resume a previously interrupted channel. [WORK IN PROGRESS] Request that the recipient issue a pong request. [WORK IN PROGRESS] Issued after a ping request is received. Note that this is a request issued after receiving a ping, not a response to receiving a ping. [WORK IN PROGRESS] Signals normal completion of a method. The protocol control access to server resources using access tickets. A client must explicitly request access tickets before doing work. An access ticket grants a client the right to use a specific set of resources - called a "realm" - in specific ways. access = C:REQUEST S:REQUEST-OK This method requests an access ticket for an access realm. The server responds by granting the access ticket. If the client does not have access rights to the requested realm this causes a connection exception. Access tickets are a per-channel resource. Specifies the name of the realm to which the client is requesting access. The realm is a configured server-side object that collects a set of resources (exchanges, queues, etc.). If the channel has already requested an access ticket onto this realm, the previous ticket is destroyed and a new ticket is created with the requested access rights, if allowed. The client MUST specify a realm that is known to the server. The server makes an identical response for undefined realms as it does for realms that are defined but inaccessible to this client. Client specifies an undefined realm. Request exclusive access to the realm, meaning that this will be the only channel that uses the realm's resources. The client MAY NOT request exclusive access to a realm that has active access tickets, unless the same channel already had the only access ticket onto that realm. Client opens two channels and requests exclusive access to the same realm. Request message passive access to the specified access realm. Passive access lets a client get information about resources in the realm but not to make any changes to them. Request message active access to the specified access realm. Active access lets a client get create and delete resources in the realm. Request write access to the specified access realm. Write access lets a client publish messages to all exchanges in the realm. Request read access to the specified access realm. Read access lets a client consume messages from queues in the realm. This method provides the client with an access ticket. The access ticket is valid within the current channel and for the lifespan of the channel. The client MUST NOT use access tickets except within the same channel as originally granted. Client opens two channels, requests a ticket on one channel, and then tries to use that ticket in a second channel. Exchanges match and distribute messages across queues. Exchanges can be configured in the server or created at runtime. exchange = C:DECLARE S:DECLARE-OK / C:DELETE S:DELETE-OK The server MUST implement these standard exchange types: fanout, direct. Client attempts to declare an exchange with each of these standard types. The server SHOULD implement these standard exchange types: topic, headers. Client attempts to declare an exchange with each of these standard types. The server MUST, in each virtual host, pre-declare an exchange instance for each standard exchange type that it implements, where the name of the exchange instance, if defined, is "amq." followed by the exchange type name. The server MUST, in each virtual host, pre-declare at least two direct exchange instances: one named "amq.direct", the other with no public name that serves as a default exchange for Publish methods. Client creates a temporary queue and attempts to bind to each required exchange instance ("amq.fanout", "amq.direct", "amq.topic", and "amq.headers" if those types are defined). The server MUST pre-declare a direct exchange with no public name to act as the default exchange for content Publish methods and for default queue bindings. Client checks that the default exchange is active by specifying a queue binding with no exchange name, and publishing a message with a suitable routing key but without specifying the exchange name, then ensuring that the message arrives in the queue correctly. The server MUST NOT allow clients to access the default exchange except by specifying an empty exchange name in the Queue.Bind and content Publish methods. The server MAY implement other exchange types as wanted. This method creates an exchange if it does not already exist, and if the exchange exists, verifies that it is of the correct and expected class. The server SHOULD support a minimum of 16 exchanges per virtual host and ideally, impose no limit except as defined by available resources. The client creates as many exchanges as it can until the server reports an error; the number of exchanges successfully created must be at least sixteen. When a client defines a new exchange, this belongs to the access realm of the ticket used. All further work done with that exchange must be done with an access ticket for the same realm. The client MUST provide a valid access ticket giving "active" access to the realm in which the exchange exists or will be created, or "passive" access if the if-exists flag is set. Client creates access ticket with wrong access rights and attempts to use in this method. Exchange names starting with "amq." are reserved for pre-declared and standardised exchanges. The client MUST NOT attempt to create an exchange starting with "amq.". TODO. Each exchange belongs to one of a set of exchange types implemented by the server. The exchange types define the functionality of the exchange - i.e. how messages are routed through it. It is not valid or meaningful to attempt to change the type of an existing exchange. Exchanges cannot be redeclared with different types. The client MUST not attempt to redeclare an existing exchange with a different type than used in the original Exchange.Declare method. TODO. The client MUST NOT attempt to create an exchange with a type that the server does not support. TODO. If set, the server will not create the exchange. The client can use this to check whether an exchange exists without modifying the server state. If set, and the exchange does not already exist, the server MUST raise a channel exception with reply code 404 (not found). TODO. If set when creating a new exchange, the exchange will be marked as durable. Durable exchanges remain active when a server restarts. Non-durable exchanges (transient exchanges) are purged if/when a server restarts. The server MUST support both durable and transient exchanges. TODO. The server MUST ignore the durable field if the exchange already exists. TODO. If set, the exchange is deleted when all queues have finished using it. The server MUST ignore the auto-delete field if the exchange already exists. TODO. If set, the exchange may not be used directly by publishers, but only when bound to other exchanges. Internal exchanges are used to construct wiring that is not visible to applications. If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. A set of arguments for the declaration. The syntax and semantics of these arguments depends on the server implementation. This field is ignored if passive is 1. This method confirms a Declare method and confirms the name of the exchange, essential for automatically-named exchanges. This method deletes an exchange. When an exchange is deleted all queue bindings on the exchange are cancelled. The client MUST provide a valid access ticket giving "active" access rights to the exchange's access realm. Client creates access ticket with wrong access rights and attempts to use in this method. The client MUST NOT attempt to delete an exchange that does not exist. If set, the server will only delete the exchange if it has no queue bindings. If the exchange has queue bindings the server does not delete it but raises a channel exception instead. If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. This method confirms the deletion of an exchange. Message routing key Specifies the routing key for the message. The routing key is used for routing messages depending on the exchange configuration. Queues store and forward messages. Queues can be configured in the server or created at runtime. Queues must be attached to at least one exchange in order to receive messages from publishers. queue = C:DECLARE S:DECLARE-OK / C:BIND S:BIND-OK / C:PURGE S:PURGE-OK / C:DELETE S:DELETE-OK A server MUST allow any content class to be sent to any queue, in any mix, and queue and deliver these content classes independently. Note that all methods that fetch content off queues are specific to a given content class. Client creates an exchange of each standard type and several queues that it binds to each exchange. It must then successfully send each of the standard content types to each of the available queues. This method creates or checks a queue. When creating a new queue the client can specify various properties that control the durability of the queue and its contents, and the level of sharing for the queue. The server MUST create a default binding for a newly-created queue to the default exchange, which is an exchange of type 'direct' and use the queue name as the routing key. Client creates a new queue, and then without explicitly binding it to an exchange, attempts to send a message through the default exchange binding, i.e. publish a message to the empty exchange, with the queue name as routing key. The server SHOULD support a minimum of 256 queues per virtual host and ideally, impose no limit except as defined by available resources. Client attempts to create as many queues as it can until the server reports an error. The resulting count must at least be 256. When a client defines a new queue, this belongs to the access realm of the ticket used. All further work done with that queue must be done with an access ticket for the same realm. The client MUST provide a valid access ticket giving "active" access to the realm in which the queue exists or will be created. Client creates access ticket with wrong access rights and attempts to use in this method. The queue name MAY be empty, in which case the server MUST create a new queue with a unique generated name and return this to the client in the Declare-Ok method. Client attempts to create several queues with an empty name. The client then verifies that the server-assigned names are unique and different. Queue names starting with "amq." are reserved for pre-declared and standardised server queues. A client MAY NOT attempt to declare a queue with a name that starts with "amq." and the passive option set to zero. A client attempts to create a queue with a name starting with "amq." and with the passive option set to zero. If set, the server will not create the queue. This field allows the client to assert the presence of a queue without modifying the server state. The client MAY ask the server to assert that a queue exists without creating the queue if not. If the queue does not exist, the server treats this as a failure. Client declares an existing queue with the passive option and expects the server to respond with a declare-ok. Client then attempts to declare a non-existent queue with the passive option, and the server must close the channel with the correct reply-code. If set when creating a new queue, the queue will be marked as durable. Durable queues remain active when a server restarts. Non-durable queues (transient queues) are purged if/when a server restarts. Note that durable queues do not necessarily hold persistent messages, although it does not make sense to send persistent messages to a transient queue. The server MUST recreate the durable queue after a restart. A client creates a durable queue. The server is then restarted. The client then attempts to send a message to the queue. The message should be successfully delivered. The server MUST support both durable and transient queues. A client creates two named queues, one durable and one transient. The server MUST ignore the durable field if the queue already exists. A client creates two named queues, one durable and one transient. The client then attempts to declare the two queues using the same names again, but reversing the value of the durable flag in each case. Verify that the queues still exist with the original durable flag values. Exclusive queues may only be consumed from by the current connection. Setting the 'exclusive' flag always implies 'auto-delete'. The server MUST support both exclusive (private) and non-exclusive (shared) queues. A client creates two named queues, one exclusive and one non-exclusive. The client MAY NOT attempt to declare any existing and exclusive queue on multiple connections. A client declares an exclusive named queue. A second client on a different connection attempts to declare a queue of the same name. If set, the queue is deleted when all consumers have finished using it. Last consumer can be cancelled either explicitly or because its channel is closed. If there was no consumer ever on the queue, it won't be deleted. The server MUST ignore the auto-delete field if the queue already exists. A client creates two named queues, one as auto-delete and one explicit-delete. The client then attempts to declare the two queues using the same names again, but reversing the value of the auto-delete field in each case. Verify that the queues still exist with the original auto-delete flag values. If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. A set of arguments for the declaration. The syntax and semantics of these arguments depends on the server implementation. This field is ignored if passive is 1. This method confirms a Declare method and confirms the name of the queue, essential for automatically-named queues. Reports the name of the queue. If the server generated a queue name, this field contains that name. Reports the number of messages in the queue, which will be zero for newly-created queues. Reports the number of active consumers for the queue. Note that consumers can suspend activity (Channel.Flow) in which case they do not appear in this count. This method binds a queue to an exchange. Until a queue is bound it will not receive any messages. In a classic messaging model, store-and-forward queues are bound to a direct exchange and subscription queues are bound to a topic exchange. A server MUST allow ignore duplicate bindings - that is, two or more bind methods for a specific queue, with identical arguments - without treating these as an error. A client binds a named queue to an exchange. The client then repeats the bind (with identical arguments). If a bind fails, the server MUST raise a connection exception. TODO The server MUST NOT allow a durable queue to bind to a transient exchange. A client creates a transient exchange. The client then declares a named durable queue and then attempts to bind the transient exchange to the durable queue. Bindings for durable queues are automatically durable and the server SHOULD restore such bindings after a server restart. A server creates a named durable queue and binds it to a durable exchange. The server is restarted. The client then attempts to use the queue/exchange combination. If the client attempts to bind to an exchange that was declared as internal, the server MUST raise a connection exception with reply code 530 (not allowed). A client attempts to bind a named queue to an internal exchange. The server SHOULD support at least 4 bindings per queue, and ideally, impose no limit except as defined by available resources. A client creates a named queue and attempts to bind it to 4 different non-internal exchanges. The client provides a valid access ticket giving "active" access rights to the queue's access realm. Specifies the name of the queue to bind. If the queue name is empty, refers to the current queue for the channel, which is the last declared queue. A client MUST NOT be allowed to bind a non-existent and unnamed queue (i.e. empty queue name) to an exchange. A client attempts to bind with an unnamed (empty) queue name to an exchange. A client MUST NOT be allowed to bind a non-existent queue (i.e. not previously declared) to an exchange. A client attempts to bind an undeclared queue name to an exchange. A client MUST NOT be allowed to bind a queue to a non-existent exchange. A client attempts to bind an named queue to a undeclared exchange. Specifies the routing key for the binding. The routing key is used for routing messages depending on the exchange configuration. Not all exchanges use a routing key - refer to the specific exchange documentation. If the queue name is empty, the server uses the last queue declared on the channel. If the routing key is also empty, the server uses this queue name for the routing key as well. If the queue name is provided but the routing key is empty, the server does the binding with that empty routing key. The meaning of empty routing keys depends on the exchange implementation. If a message queue binds to a direct exchange using routing key K and a publisher sends the exchange a message with routing key R, then the message MUST be passed to the message queue if K = R. If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. A set of arguments for the binding. The syntax and semantics of these arguments depends on the exchange class. This method confirms that the bind was successful. This method unbinds a queue from an exchange. If a unbind fails, the server MUST raise a connection exception. The client provides a valid access ticket giving "active" access rights to the queue's access realm. Specifies the name of the queue to unbind. If the queue does not exist the server MUST raise a channel exception with reply code 404 (not found). The name of the exchange to unbind from. If the exchange does not exist the server MUST raise a channel exception with reply code 404 (not found). Specifies the routing key of the binding to unbind. Specifies the arguments of the binding to unbind. This method confirms that the unbind was successful. This method removes all messages from a queue. It does not cancel consumers. Purged messages are deleted without any formal "undo" mechanism. A call to purge MUST result in an empty queue. On transacted channels the server MUST not purge messages that have already been sent to a client but not yet acknowledged. The server MAY implement a purge queue or log that allows system administrators to recover accidentally-purged messages. The server SHOULD NOT keep purged messages in the same storage spaces as the live messages since the volumes of purged messages may get very large. The access ticket must be for the access realm that holds the queue. The client MUST provide a valid access ticket giving "read" access rights to the queue's access realm. Note that purging a queue is equivalent to reading all messages and discarding them. Specifies the name of the queue to purge. If the queue name is empty, refers to the current queue for the channel, which is the last declared queue. If the client did not previously declare a queue, and the queue name in this method is empty, the server MUST raise a connection exception with reply code 530 (not allowed). The queue MUST exist. Attempting to purge a non-existing queue MUST cause a channel exception. If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. This method confirms the purge of a queue. Reports the number of messages purged. This method deletes a queue. When a queue is deleted any pending messages are sent to a dead-letter queue if this is defined in the server configuration, and all consumers on the queue are cancelled. The server SHOULD use a dead-letter queue to hold messages that were pending on a deleted queue, and MAY provide facilities for a system administrator to move these messages back to an active queue. The client provides a valid access ticket giving "active" access rights to the queue's access realm. Specifies the name of the queue to delete. If the queue name is empty, refers to the current queue for the channel, which is the last declared queue. If the client did not previously declare a queue, and the queue name in this method is empty, the server MUST raise a connection exception with reply code 530 (not allowed). The queue must exist. If the client attempts to delete a non-existing queue the server MUST raise a channel exception with reply code 404 (not found). If set, the server will only delete the queue if it has no consumers. If the queue has consumers the server does does not delete it but raises a channel exception instead. The server MUST respect the if-unused flag when deleting a queue. If set, the server will only delete the queue if it has no messages. If the queue is not empty the server MUST raise a channel exception with reply code 406 (precondition failed). If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. This method confirms the deletion of a queue. Reports the number of messages purged. The Basic class provides methods that support an industry-standard messaging model. basic = C:QOS S:QOS-OK / C:CONSUME S:CONSUME-OK / C:CANCEL S:CANCEL-OK / C:PUBLISH content / S:RETURN content / S:DELIVER content / C:GET ( S:GET-OK content / S:GET-EMPTY ) / C:ACK / C:REJECT The server SHOULD respect the persistent property of basic messages and SHOULD make a best-effort to hold persistent basic messages on a reliable storage mechanism. Send a persistent message to queue, stop server, restart server and then verify whether message is still present. Assumes that queues are durable. Persistence without durable queues makes no sense. The server MUST NOT discard a persistent basic message in case of a queue overflow. Create a queue overflow situation with persistent messages and verify that messages do not get lost (presumably the server will write them to disk). The server MAY use the Channel.Flow method to slow or stop a basic message publisher when necessary. Create a queue overflow situation with non-persistent messages and verify whether the server responds with Channel.Flow or not. Repeat with persistent messages. The server MAY overflow non-persistent basic messages to persistent storage. The server MAY discard or dead-letter non-persistent basic messages on a priority basis if the queue size exceeds some configured limit. The server MUST implement at least 2 priority levels for basic messages, where priorities 0-4 and 5-9 are treated as two distinct levels. Send a number of priority 0 messages to a queue. Send one priority 9 message. Consume messages from the queue and verify that the first message received was priority 9. The server MAY implement up to 10 priority levels. Send a number of messages with mixed priorities to a queue, so that all priority values from 0 to 9 are exercised. A good scenario would be ten messages in low-to-high priority. Consume from queue and verify how many priority levels emerge. The server MUST deliver messages of the same priority in order irrespective of their individual persistence. Send a set of messages with the same priority but different persistence settings to a queue. Consume and verify that messages arrive in same order as originally published. The server MUST support automatic acknowledgements on Basic content, i.e. consumers with the no-ack field set to FALSE. Create a queue and a consumer using automatic acknowledgements. Publish a set of messages to the queue. Consume the messages and verify that all messages are received. The server MUST support explicit acknowledgements on Basic content, i.e. consumers with the no-ack field set to TRUE. Create a queue and a consumer using explicit acknowledgements. Publish a set of messages to the queue. Consume the messages but acknowledge only half of them. Disconnect and reconnect, and consume from the queue. Verify that the remaining messages are received. This method requests a specific quality of service. The QoS can be specified for the current channel or for all channels on the connection. The particular properties and semantics of a qos method always depend on the content class semantics. Though the qos method could in principle apply to both peers, it is currently meaningful only for the server. The client can request that messages be sent in advance so that when the client finishes processing a message, the following message is already held locally, rather than needing to be sent down the channel. Prefetching gives a performance improvement. This field specifies the prefetch window size in octets. The server will send a message in advance if it is equal to or smaller in size than the available prefetch size (and also falls into other prefetch limits). May be set to zero, meaning "no specific limit", although other prefetch limits may still apply. The prefetch-size is ignored if the no-ack option is set. The server MUST ignore this setting when the client is not processing any messages - i.e. the prefetch size does not limit the transfer of single messages to a client, only the sending in advance of more messages while the client still has one or more unacknowledged messages. Define a QoS prefetch-size limit and send a single message that exceeds that limit. Verify that the message arrives correctly. Specifies a prefetch window in terms of whole messages. This field may be used in combination with the prefetch-size field; a message will only be sent in advance if both prefetch windows (and those at the channel and connection level) allow it. The prefetch-count is ignored if the no-ack option is set. The server may send less data in advance than allowed by the client's specified prefetch windows but it MUST NOT send more. Define a QoS prefetch-size limit and a prefetch-count limit greater than one. Send multiple messages that exceed the prefetch size. Verify that no more than one message arrives at once. By default the QoS settings apply to the current channel only. If this field is set, they are applied to the entire connection. This method tells the client that the requested QoS levels could be handled by the server. The requested QoS applies to all active consumers until a new QoS is defined. This method asks the server to start a "consumer", which is a transient request for messages from a specific queue. Consumers last as long as the channel they were created on, or until the client cancels them. The server SHOULD support at least 16 consumers per queue, and ideally, impose no limit except as defined by available resources. Create a queue and create consumers on that queue until the server closes the connection. Verify that the number of consumers created was at least sixteen and report the total number. The client MUST provide a valid access ticket giving "read" access rights to the realm for the queue. Attempt to create a consumer with an invalid (non-zero) access ticket. Specifies the name of the queue to consume from. If the queue name is null, refers to the current queue for the channel, which is the last declared queue. If the queue name is empty the client MUST have previously declared a queue using this channel. Attempt to create a consumer with an empty queue name and no previously declared queue on the channel. Specifies the identifier for the consumer. The consumer tag is local to a connection, so two clients can use the same consumer tags. If this field is empty the server will generate a unique tag. The client MUST NOT specify a tag that refers to an existing consumer. Attempt to create two consumers with the same non-empty tag. The consumer tag is valid only within the channel from which the consumer was created. I.e. a client MUST NOT create a consumer in one channel and then use it in another. Attempt to create a consumer in one channel, then use in another channel, in which consumers have also been created (to test that the server uses unique consumer tags). Request exclusive consumer access, meaning only this consumer can access the queue. The client MAY NOT gain exclusive access to a queue that already has active consumers. Open two connections to a server, and in one connection create a shared (non-exclusive) queue and then consume from the queue. In the second connection attempt to consume from the same queue using the exclusive option. If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. A set of filters for the consume. The syntax and semantics of these filters depends on the providers implementation. The server provides the client with a consumer tag, which is used by the client for methods called on the consumer at a later stage. Holds the consumer tag specified by the client or provided by the server. This method cancels a consumer. This does not affect already delivered messages, but it does mean the server will not send any more messages for that consumer. The client may receive an arbitrary number of messages in between sending the cancel method and receiving the cancel-ok reply. If the queue does not exist the server MUST ignore the cancel method, so long as the consumer tag is valid for that channel. TODO. If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. This method confirms that the cancellation was completed. This method publishes a message to a specific exchange. The message will be routed to queues as defined by the exchange configuration and distributed to any active consumers when the transaction, if any, is committed. The client MUST provide a valid access ticket giving "write" access rights to the access realm for the exchange. TODO. Specifies the name of the exchange to publish to. The exchange name can be empty, meaning the default exchange. If the exchange name is specified, and that exchange does not exist, the server will raise a channel exception. The server MUST accept a blank exchange name to mean the default exchange. TODO. If the exchange was declared as an internal exchange, the server MUST raise a channel exception with a reply code 403 (access refused). TODO. The exchange MAY refuse basic content in which case it MUST raise a channel exception with reply code 540 (not implemented). TODO. Specifies the routing key for the message. The routing key is used for routing messages depending on the exchange configuration. This flag tells the server how to react if the message cannot be routed to a queue. If this flag is set, the server will return an unroutable message with a Return method. If this flag is zero, the server silently drops the message. The server SHOULD implement the mandatory flag. TODO. This flag tells the server how to react if the message cannot be routed to a queue consumer immediately. If this flag is set, the server will return an undeliverable message with a Return method. If this flag is zero, the server will queue the message, but with no guarantee that it will ever be consumed. The server SHOULD implement the immediate flag. TODO. This method returns an undeliverable message that was published with the "immediate" flag set, or an unroutable message published with the "mandatory" flag set. The reply code and text provide information about the reason that the message was undeliverable. Specifies the name of the exchange that the message was originally published to. Specifies the routing key name specified when the message was published. This method delivers a message to the client, via a consumer. In the asynchronous message delivery model, the client starts a consumer using the Consume method, then the server responds with Deliver methods as and when messages arrive for that consumer. The server SHOULD track the number of times a message has been delivered to clients and when a message is redelivered a certain number of times - e.g. 5 times - without being acknowledged, the server SHOULD consider the message to be unprocessable (possibly causing client applications to abort), and move the message to a dead letter queue. TODO. Specifies the name of the exchange that the message was originally published to. Specifies the routing key name specified when the message was published. This method provides a direct access to the messages in a queue using a synchronous dialogue that is designed for specific types of application where synchronous functionality is more important than performance. The client MUST provide a valid access ticket giving "read" access rights to the realm for the queue. TODO. Specifies the name of the queue to consume from. If the queue name is null, refers to the current queue for the channel, which is the last declared queue. If the client did not previously declare a queue, and the queue name in this method is empty, the server MUST raise a connection exception with reply code 530 (not allowed). TODO. This method delivers a message to the client following a get method. A message delivered by 'get-ok' must be acknowledged unless the no-ack option was set in the get method. Specifies the name of the exchange that the message was originally published to. If empty, the message was published to the default exchange. Specifies the routing key name specified when the message was published. This field reports the number of messages pending on the queue, excluding the message being delivered. Note that this figure is indicative, not reliable, and can change arbitrarily as messages are added to the queue and removed by other clients. This method tells the client that the queue has no messages available for the client. For use by cluster applications, should not be used by client applications. This method acknowledges one or more messages delivered via the Deliver or Get-Ok methods. The client can ask to confirm a single message or a set of messages up to and including a specific message. If set to 1, the delivery tag is treated as "up to and including", so that the client can acknowledge multiple messages with a single method. If set to zero, the delivery tag refers to a single message. If the multiple field is 1, and the delivery tag is zero, tells the server to acknowledge all outstanding messages. The server MUST validate that a non-zero delivery-tag refers to an delivered message, and raise a channel exception if this is not the case. TODO. This method allows a client to reject a message. It can be used to interrupt and cancel large incoming messages, or return untreatable messages to their original queue. The server SHOULD be capable of accepting and process the Reject method while sending message content with a Deliver or Get-Ok method. I.e. the server should read and process incoming methods while sending output frames. To cancel a partially-send content, the server sends a content body frame of size 1 (i.e. with no data except the frame-end octet). The server SHOULD interpret this method as meaning that the client is unable to process the message at this time. TODO. A client MUST NOT use this method as a means of selecting messages to process. A rejected message MAY be discarded or dead-lettered, not necessarily passed to another client. TODO. If this field is zero, the message will be discarded. If this bit is 1, the server will attempt to requeue the message. The server MUST NOT deliver the message to the same client within the context of the current channel. The recommended strategy is to attempt to deliver the message to an alternative consumer, and if that is not possible, to move the message to a dead-letter queue. The server MAY use more sophisticated tracking to hold the message on the queue and redeliver it to the same client at a later stage. TODO. This method asks the broker to redeliver all unacknowledged messages on a specified channel. Zero or more messages may be redelivered. This method is only allowed on non-transacted channels. The server MUST set the redelivered flag on all messages that are resent. TODO. The server MUST raise a channel exception if this is called on a transacted channel. TODO. If this field is zero, the message will be redelivered to the original recipient. If this bit is 1, the server will attempt to requeue the message, potentially then delivering it to an alternative subscriber. redeliver unacknowledged messages This method asks the broker to redeliver all unacknowledged messages on a specified channel. Zero or more messages may be redelivered. This method is only allowed on non-transacted channels. requeue the message If this field is zero, the message will be redelivered to the original recipient. If this bit is 1, the server will attempt to requeue the message, potentially then delivering it to an alternative subscriber. The server MUST set the redelivered flag on all messages that are resent. The server MUST raise a channel exception if this is called on a transacted channel. confirm a successful recover This method confirms to the client that the recover succeeded. Note that if an recover fails, the server raises a channel exception. The file class provides methods that support reliable file transfer. File messages have a specific set of properties that are required for interoperability with file transfer applications. File messages and acknowledgements are subject to channel transactions. Note that the file class does not provide message browsing methods; these are not compatible with the staging model. Applications that need browsable file transfer should use Basic content and the Basic class. file = C:QOS S:QOS-OK / C:CONSUME S:CONSUME-OK / C:CANCEL S:CANCEL-OK / C:OPEN S:OPEN-OK C:STAGE content / S:OPEN C:OPEN-OK S:STAGE content / C:PUBLISH / S:DELIVER / S:RETURN / C:ACK / C:REJECT The server MUST make a best-effort to hold file messages on a reliable storage mechanism. The server MUST NOT discard a file message in case of a queue overflow. The server MUST use the Channel.Flow method to slow or stop a file message publisher when necessary. The server MUST implement at least 2 priority levels for file messages, where priorities 0-4 and 5-9 are treated as two distinct levels. The server MAY implement up to 10 priority levels. The server MUST support both automatic and explicit acknowledgements on file content. This method requests a specific quality of service. The QoS can be specified for the current channel or for all channels on the connection. The particular properties and semantics of a qos method always depend on the content class semantics. Though the qos method could in principle apply to both peers, it is currently meaningful only for the server. The client can request that messages be sent in advance so that when the client finishes processing a message, the following message is already held locally, rather than needing to be sent down the channel. Prefetching gives a performance improvement. This field specifies the prefetch window size in octets. May be set to zero, meaning "no specific limit". Note that other prefetch limits may still apply. The prefetch-size is ignored if the no-ack option is set. Specifies a prefetch window in terms of whole messages. This is compatible with some file API implementations. This field may be used in combination with the prefetch-size field; a message will only be sent in advance if both prefetch windows (and those at the channel and connection level) allow it. The prefetch-count is ignored if the no-ack option is set. The server MAY send less data in advance than allowed by the client's specified prefetch windows but it MUST NOT send more. By default the QoS settings apply to the current channel only. If this field is set, they are applied to the entire connection. This method tells the client that the requested QoS levels could be handled by the server. The requested QoS applies to all active consumers until a new QoS is defined. This method asks the server to start a "consumer", which is a transient request for messages from a specific queue. Consumers last as long as the channel they were created on, or until the client cancels them. The server SHOULD support at least 16 consumers per queue, unless the queue was declared as private, and ideally, impose no limit except as defined by available resources. The client MUST provide a valid access ticket giving "read" access rights to the realm for the queue. Specifies the name of the queue to consume from. If the queue name is null, refers to the current queue for the channel, which is the last declared queue. If the client did not previously declare a queue, and the queue name in this method is empty, the server MUST raise a connection exception with reply code 530 (not allowed). Specifies the identifier for the consumer. The consumer tag is local to a connection, so two clients can use the same consumer tags. If this field is empty the server will generate a unique tag. The tag MUST NOT refer to an existing consumer. If the client attempts to create two consumers with the same non-empty tag the server MUST raise a connection exception with reply code 530 (not allowed). Request exclusive consumer access, meaning only this consumer can access the queue. If the server cannot grant exclusive access to the queue when asked, - because there are other consumers active - it MUST raise a channel exception with return code 405 (resource locked). If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. A set of filters for the consume. The syntax and semantics of these filters depends on the providers implementation. This method provides the client with a consumer tag which it MUST use in methods that work with the consumer. Holds the consumer tag specified by the client or provided by the server. This method cancels a consumer. This does not affect already delivered messages, but it does mean the server will not send any more messages for that consumer. If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. This method confirms that the cancellation was completed. This method requests permission to start staging a message. Staging means sending the message into a temporary area at the recipient end and then delivering the message by referring to this temporary area. Staging is how the protocol handles partial file transfers - if a message is partially staged and the connection breaks, the next time the sender starts to stage it, it can restart from where it left off. This is the staging identifier. This is an arbitrary string chosen by the sender. For staging to work correctly the sender must use the same staging identifier when staging the same message a second time after recovery from a failure. A good choice for the staging identifier would be the SHA1 hash of the message properties data (including the original filename, revised time, etc.). The size of the content in octets. The recipient may use this information to allocate or check available space in advance, to avoid "disk full" errors during staging of very large messages. The sender MUST accurately fill the content-size field. Zero-length content is permitted. This method confirms that the recipient is ready to accept staged data. If the message was already partially-staged at a previous time the recipient will report the number of octets already staged. The amount of previously-staged content in octets. For a new message this will be zero. The sender MUST start sending data from this octet offset in the message, counting from zero. The recipient MAY decide how long to hold partially-staged content and MAY implement staging by always discarding partially-staged content. However if it uses the file content type it MUST support the staging methods. This method stages the message, sending the message content to the recipient from the octet offset specified in the Open-Ok method. This method publishes a staged file message to a specific exchange. The file message will be routed to queues as defined by the exchange configuration and distributed to any active consumers when the transaction, if any, is committed. The client MUST provide a valid access ticket giving "write" access rights to the access realm for the exchange. Specifies the name of the exchange to publish to. The exchange name can be empty, meaning the default exchange. If the exchange name is specified, and that exchange does not exist, the server will raise a channel exception. The server MUST accept a blank exchange name to mean the default exchange. If the exchange was declared as an internal exchange, the server MUST respond with a reply code 403 (access refused) and raise a channel exception. The exchange MAY refuse file content in which case it MUST respond with a reply code 540 (not implemented) and raise a channel exception. Specifies the routing key for the message. The routing key is used for routing messages depending on the exchange configuration. This flag tells the server how to react if the message cannot be routed to a queue. If this flag is set, the server will return an unroutable message with a Return method. If this flag is zero, the server silently drops the message. The server SHOULD implement the mandatory flag. This flag tells the server how to react if the message cannot be routed to a queue consumer immediately. If this flag is set, the server will return an undeliverable message with a Return method. If this flag is zero, the server will queue the message, but with no guarantee that it will ever be consumed. The server SHOULD implement the immediate flag. This is the staging identifier of the message to publish. The message must have been staged. Note that a client can send the Publish method asynchronously without waiting for staging to finish. This method returns an undeliverable message that was published with the "immediate" flag set, or an unroutable message published with the "mandatory" flag set. The reply code and text provide information about the reason that the message was undeliverable. Specifies the name of the exchange that the message was originally published to. Specifies the routing key name specified when the message was published. This method delivers a staged file message to the client, via a consumer. In the asynchronous message delivery model, the client starts a consumer using the Consume method, then the server responds with Deliver methods as and when messages arrive for that consumer. The server SHOULD track the number of times a message has been delivered to clients and when a message is redelivered a certain number of times - e.g. 5 times - without being acknowledged, the server SHOULD consider the message to be unprocessable (possibly causing client applications to abort), and move the message to a dead letter queue. Specifies the name of the exchange that the message was originally published to. Specifies the routing key name specified when the message was published. This is the staging identifier of the message to deliver. The message must have been staged. Note that a server can send the Deliver method asynchronously without waiting for staging to finish. This method acknowledges one or more messages delivered via the Deliver method. The client can ask to confirm a single message or a set of messages up to and including a specific message. If set to 1, the delivery tag is treated as "up to and including", so that the client can acknowledge multiple messages with a single method. If set to zero, the delivery tag refers to a single message. If the multiple field is 1, and the delivery tag is zero, tells the server to acknowledge all outstanding messages. The server MUST validate that a non-zero delivery-tag refers to an delivered message, and raise a channel exception if this is not the case. This method allows a client to reject a message. It can be used to return untreatable messages to their original queue. Note that file content is staged before delivery, so the client will not use this method to interrupt delivery of a large message. The server SHOULD interpret this method as meaning that the client is unable to process the message at this time. A client MUST NOT use this method as a means of selecting messages to process. A rejected message MAY be discarded or dead-lettered, not necessarily passed to another client. If this field is zero, the message will be discarded. If this bit is 1, the server will attempt to requeue the message. The server MUST NOT deliver the message to the same client within the context of the current channel. The recommended strategy is to attempt to deliver the message to an alternative consumer, and if that is not possible, to move the message to a dead-letter queue. The server MAY use more sophisticated tracking to hold the message on the queue and redeliver it to the same client at a later stage. The stream class provides methods that support multimedia streaming. The stream class uses the following semantics: one message is one packet of data; delivery is unacknowledged and unreliable; the consumer can specify quality of service parameters that the server can try to adhere to; lower-priority messages may be discarded in favour of high priority messages. stream = C:QOS S:QOS-OK / C:CONSUME S:CONSUME-OK / C:CANCEL S:CANCEL-OK / C:PUBLISH content / S:RETURN / S:DELIVER content The server SHOULD discard stream messages on a priority basis if the queue size exceeds some configured limit. The server MUST implement at least 2 priority levels for stream messages, where priorities 0-4 and 5-9 are treated as two distinct levels. The server MAY implement up to 10 priority levels. The server MUST implement automatic acknowledgements on stream content. That is, as soon as a message is delivered to a client via a Deliver method, the server must remove it from the queue. This method requests a specific quality of service. The QoS can be specified for the current channel or for all channels on the connection. The particular properties and semantics of a qos method always depend on the content class semantics. Though the qos method could in principle apply to both peers, it is currently meaningful only for the server. The client can request that messages be sent in advance so that when the client finishes processing a message, the following message is already held locally, rather than needing to be sent down the channel. Prefetching gives a performance improvement. This field specifies the prefetch window size in octets. May be set to zero, meaning "no specific limit". Note that other prefetch limits may still apply. Specifies a prefetch window in terms of whole messages. This field may be used in combination with the prefetch-size field; a message will only be sent in advance if both prefetch windows (and those at the channel and connection level) allow it. Specifies a desired transfer rate in octets per second. This is usually determined by the application that uses the streaming data. A value of zero means "no limit", i.e. as rapidly as possible. The server MAY ignore the prefetch values and consume rates, depending on the type of stream and the ability of the server to queue and/or reply it. The server MAY drop low-priority messages in favour of high-priority messages. By default the QoS settings apply to the current channel only. If this field is set, they are applied to the entire connection. This method tells the client that the requested QoS levels could be handled by the server. The requested QoS applies to all active consumers until a new QoS is defined. This method asks the server to start a "consumer", which is a transient request for messages from a specific queue. Consumers last as long as the channel they were created on, or until the client cancels them. The server SHOULD support at least 16 consumers per queue, unless the queue was declared as private, and ideally, impose no limit except as defined by available resources. Streaming applications SHOULD use different channels to select different streaming resolutions. AMQP makes no provision for filtering and/or transforming streams except on the basis of priority-based selective delivery of individual messages. The client MUST provide a valid access ticket giving "read" access rights to the realm for the queue. Specifies the name of the queue to consume from. If the queue name is null, refers to the current queue for the channel, which is the last declared queue. If the client did not previously declare a queue, and the queue name in this method is empty, the server MUST raise a connection exception with reply code 530 (not allowed). Specifies the identifier for the consumer. The consumer tag is local to a connection, so two clients can use the same consumer tags. If this field is empty the server will generate a unique tag. The tag MUST NOT refer to an existing consumer. If the client attempts to create two consumers with the same non-empty tag the server MUST raise a connection exception with reply code 530 (not allowed). Request exclusive consumer access, meaning only this consumer can access the queue. If the server cannot grant exclusive access to the queue when asked, - because there are other consumers active - it MUST raise a channel exception with return code 405 (resource locked). If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. A set of filters for the consume. The syntax and semantics of these filters depends on the providers implementation. This method provides the client with a consumer tag which it may use in methods that work with the consumer. Holds the consumer tag specified by the client or provided by the server. This method cancels a consumer. Since message delivery is asynchronous the client may continue to receive messages for a short while after cancelling a consumer. It may process or discard these as appropriate. If set, the server will not respond to the method. The client should not wait for a reply method. If the server could not complete the method it will raise a channel or connection exception. This method confirms that the cancellation was completed. This method publishes a message to a specific exchange. The message will be routed to queues as defined by the exchange configuration and distributed to any active consumers as appropriate. The client MUST provide a valid access ticket giving "write" access rights to the access realm for the exchange. Specifies the name of the exchange to publish to. The exchange name can be empty, meaning the default exchange. If the exchange name is specified, and that exchange does not exist, the server will raise a channel exception. The server MUST accept a blank exchange name to mean the default exchange. If the exchange was declared as an internal exchange, the server MUST respond with a reply code 403 (access refused) and raise a channel exception. The exchange MAY refuse stream content in which case it MUST respond with a reply code 540 (not implemented) and raise a channel exception. Specifies the routing key for the message. The routing key is used for routing messages depending on the exchange configuration. This flag tells the server how to react if the message cannot be routed to a queue. If this flag is set, the server will return an unroutable message with a Return method. If this flag is zero, the server silently drops the message. The server SHOULD implement the mandatory flag. This flag tells the server how to react if the message cannot be routed to a queue consumer immediately. If this flag is set, the server will return an undeliverable message with a Return method. If this flag is zero, the server will queue the message, but with no guarantee that it will ever be consumed. The server SHOULD implement the immediate flag. This method returns an undeliverable message that was published with the "immediate" flag set, or an unroutable message published with the "mandatory" flag set. The reply code and text provide information about the reason that the message was undeliverable. Specifies the name of the exchange that the message was originally published to. Specifies the routing key name specified when the message was published. This method delivers a message to the client, via a consumer. In the asynchronous message delivery model, the client starts a consumer using the Consume method, then the server responds with Deliver methods as and when messages arrive for that consumer. Specifies the name of the exchange that the message was originally published to. Specifies the name of the queue that the message came from. Note that a single channel can start many consumers on different queues. Standard transactions provide so-called "1.5 phase commit". We can ensure that work is never lost, but there is a chance of confirmations being lost, so that messages may be resent. Applications that use standard transactions must be able to detect and ignore duplicate messages. An client using standard transactions SHOULD be able to track all messages received within a reasonable period, and thus detect and reject duplicates of the same message. It SHOULD NOT pass these to the application layer. tx = C:SELECT S:SELECT-OK / C:COMMIT S:COMMIT-OK / C:ROLLBACK S:ROLLBACK-OK This method sets the channel to use standard transactions. The client must use this method at least once on a channel before using the Commit or Rollback methods. This method confirms to the client that the channel was successfully set to use standard transactions. This method commits all messages published and acknowledged in the current transaction. A new transaction starts immediately after a commit. This method confirms to the client that the commit succeeded. Note that if a commit fails, the server raises a channel exception. This method abandons all messages published and acknowledged in the current transaction. A new transaction starts immediately after a rollback. This method confirms to the client that the rollback succeeded. Note that if an rollback fails, the server raises a channel exception. Distributed transactions provide so-called "2-phase commit". The AMQP distributed transaction model supports the X-Open XA architecture and other distributed transaction implementations. The Dtx class assumes that the server has a private communications channel (not AMQP) to a distributed transaction coordinator. dtx = C:SELECT S:SELECT-OK C:START S:START-OK This method sets the channel to use distributed transactions. The client must use this method at least once on a channel before using the Start method. This method confirms to the client that the channel was successfully set to use distributed transactions. This method starts a new distributed transaction. This must be the first method on a new channel that uses the distributed transaction mode, before any methods that publish or consume messages. The distributed transaction key. This identifies the transaction so that the AMQP server can coordinate with the distributed transaction coordinator. This method confirms to the client that the transaction started. Note that if a start fails, the server raises a channel exception. The tunnel methods are used to send blocks of binary data - which can be serialised AMQP methods or other protocol frames - between AMQP peers. tunnel = C:REQUEST / S:REQUEST This method tunnels a block of binary data, which can be an encoded AMQP method or other data. The binary data is sent as the content for the Tunnel.Request method. This field table holds arbitrary meta-data that the sender needs to pass to the recipient. [WORK IN PROGRESS] The message class provides methods that support an industry-standard messaging model. message = C:QOS S:OK / C:CONSUME S:OK / C:CANCEL S:OK / C:TRANSFER ( S:OK / S:REJECT ) / S:TRANSFER ( C:OK / C:REJECT ) / C:GET ( S:OK / S:EMPTY ) / C:RECOVER S:OK / C:OPEN S:OK / S:OPEN C:OK / C:APPEND S:OK / S:APPEND C:OK / C:CLOSE S:OK / S:CLOSE C:OK / C:CHECKPOINT S:OK / S:CHECKPOINT C:OK / C:RESUME S:OFFSET / S:RESUME C:OFFSET The server SHOULD respect the persistent property of messages and SHOULD make a best-effort to hold persistent mess ages on a reliable storage mechanism. Send a persistent message to queue, stop server, restart server and then verify whether message is still present. Assumes that queues are durable. Persistence without durable queues makes no sense. The server MUST NOT discard a persistent message in case of a queue overflow. Create a queue overflow situation with persistent messages and verify that messages do not get lost (presumably the server will write them to disk). The server MAY use the Channel.Flow method to slow or stop a message publisher when necessary. Create a queue overflow situation with non-persistent messages and verify whether the server responds with Channel.Flow or not. Repeat with persistent messages. The server MAY overflow non-persistent messages to persistent storage. The server MAY discard or dead-letter non-persistent messages on a priority basis if the queue size exceeds some configured limit. The server MUST implement at least 2 priority levels for messages, where priorities 0-4 and 5-9 are treated as two distinct levels. Send a number of priority 0 messages to a queue. Send one priority 9 message. Consume messages from the queue and verify that the first message received was priority 9. The server MAY implement up to 10 priority levels. Send a number of messages with mixed priorities to a queue, so that all priority values from 0 to 9 are exercised. A good scenario would be ten messages in low-to-high priority. Consume from queue and verify how many priority levels emerge. The server MUST deliver messages of the same priority in order irrespective of their individual persistence. Send a set of messages with the same priority but different persistence settings to a queue. Consume and verify that messages arrive in same order as originally published. The server MUST support automatic acknowledgements on messages, i.e. consumers with the no-ack field set to FALSE. Create a queue and a consumer using automatic acknowledgements. Publish a set of messages to the queue. Consume the messages and verify that all messages are received. The server MUST support explicit acknowledgements on messages, i.e. consumers with the no-ack field set to TRUE. Create a queue and a consumer using explicit acknowledgements. Publish a set of messages to the queue. Consume the messages but acknowledge only half of them. Disconnect and reconnect, and consume from the queue. Verify that the remaining messages are received. [WORK IN PROGRESS] This method transfers a message between two peers. When a client uses this method to publish a message to a broker, the destination identifies a specific exchange. The message will then be routed to queues as defined by the exchange configuration and distributed to any active consumers when the transaction, if any, is committed. In the asynchronous message delivery model, the client starts a consumer using the Consume method and passing in a destination, then the broker responds with transfer methods to the specified destination as and when messages arrive for that consumer. If synchronous message delivery is required, the client may issue a get request which on success causes a single message to be transferred to the specified destination. Message acknowledgement is signalled by the return result of this method. The recipient MUST NOT return ok before the message has been processed as defined by the QoS settings. The client MUST provide a valid access ticket giving "write" access rights to the access realm for the exchange. Specifies the destination to which the message is to be transferred. The destination can be empty, meaning the default exchange or consumer. If the destination is specified, and that exchange or consumer does not exist, the peer must raise a channel exception. The server MUST accept a blank destination to mean the default exchange. If the destination refers to an internal exchange, the server MUST raise a channel exception with a reply code 403 (access refused). A destination MAY refuse message content in which case it MUST raise a channel exception with reply code 540 (not implemented). This flag tells the server how to react if the message cannot be routed to a queue consumer immediately. If this flag is set, the server will reject the message. If this flag is zero, the server will queue the message, but with no guarantee that it will ever be consumed. The server SHOULD implement the immediate flag. If this is set to a non zero value then a message expiration time will be computed based on the current time plus this value. Messages that live longer than their expiration time will be discarded (or dead lettered). If a message is transfered between brokers before delivery to a final consumer the ttl should be decremented before peer to peer transfer and both timestamp and expiration should be cleared. Set on arrival by the broker. The expiration header assigned by the broker. After receiving the message the broker sets expiration to the sum of the ttl specified in the publish method and the current time. (ttl = expiration - timestamp) [WORK IN PROGRESS] This method asks the server to start a "consumer", which is a transient request for messages from a specific queue. Consumers last as long as the channel they were created on, or until the client cancels them. The server SHOULD support at least 16 consumers per queue, and ideally, impose no limit except as defined by available resources. Create a queue and create consumers on that queue until the server closes the connection. Verify that the number of consumers created was at least sixteen and report the total number. The client MUST provide a valid access ticket giving "read" access rights to the realm for the queue. Attempt to create a consumer with an invalid (non-zero) access ticket. Specifies the name of the queue to consume from. If the queue name is null, refers to the current queue for the channel, which is the last declared queue. If the queue name is empty the client MUST have previously declared a queue using this channel. Attempt to create a consumer with an empty queue name and no previously declared queue on the channel. Specifies the destination for the consumer. The destination is local to a connection, so two clients can use the same destination. The client MUST NOT specify a destination that refers to an existing consumer. Attempt to create two consumers with the same non-empty destination. The destination is valid only within the channel from which the consumer was created. I.e. a client MUST NOT create a consumer in one channel and then use it in another. Attempt to create a consumer in one channel, then use in another channel, in which consumers have also been created (to test that the server uses unique destinations). Request exclusive consumer access, meaning only this consumer can access the queue. The client MAY NOT gain exclusive access to a queue that already has active consumers. Open two connections to a server, and in one connection create a shared (non-exclusive) queue and then consume from the queue. In the second connection attempt to consume from the same queue using the exclusive option. A set of filters for the consume. The syntax and semantics of these filters depends on the providers implementation. [WORK IN PROGRESS] This method cancels a consumer. This does not affect already delivered messages, but it does mean the server will not send any more messages for that consumer. The client may receive an arbitrary number of messages in between sending the cancel method and receiving the cancel-ok reply. If the queue does not exist the server MUST ignore the cancel method, so long as the consumer tag is valid for that channel. [WORK IN PROGRESS] This method provides a direct access to the messages in a queue using a synchronous dialogue that is designed for specific types of application where synchronous functionality is more important than performance. The client MUST provide a valid access ticket giving "read" access rights to the realm for the queue. Specifies the name of the queue to consume from. If the queue name is null, refers to the current queue for the channel, which is the last declared queue. If the client did not previously declare a queue, and the queue name in this method is empty, the server MUST raise a connection exception with reply code 530 (not allowed). On normal completion of the get request (i.e. a response of ok). A message will be transferred to the supplied destination. [WORK IN PROGRESS] This method asks the broker to redeliver all unacknowledged messages on a specified channel. Zero or more messages may be redelivered. This method is only allowed on non-transacted channels. The server MUST set the redelivered flag on all messages that are resent. The server MUST raise a channel exception if this is called on a transacted channel. If this field is zero, the message will be redelivered to the original recipient. If this bit is 1, the server will attempt to requeue the message, potentially then delivering it to an alternative subscriber. [WORK IN PROGRESS] This method creates a reference. A references provides a means to send a message body into a temporary area at the recipient end and then deliver the message by referring to this temporary area. This is how the protocol handles large message transfers. The scope of a ref is defined to be between calls to open (or resume) and close. Between these points it is valid for a ref to be used from any content data type, and so the receiver must hold onto its contents. Should the channel be closed when a ref is still in scope, the receiver may discard its contents (unless it is checkpointed). A ref that is in scope is considered open. The recipient MUST generate an error if the reference is currently open (in scope). [WORK IN PROGRESS] This method signals the recipient that no more data will be appended to the reference. A recipient CANNOT acknowledge a message until its reference is closed (not in scope). The recipient MUST generate an error if the reference was not previously open (in scope). [WORK IN PROGRESS] This method appends data to a reference. The recipient MUST generate an error if the reference is not open (not in scope). [WORK IN PROGRESS] This method provides a means to checkpoint large message transfer. The sender may ask the recipient to checkpoint the contents of a reference using the supplied identifier. The sender may then resume the transfer at a later point. It is at the discretion of the recipient how much data to save with the checkpoint, and the sender MUST honour the offset returned by the resume method. The recipient MUST generate an error if the reference is not open (not in scope). This is the checkpoint identifier. This is an arbitrary string chosen by the sender. For checkpointing to work correctly the sender must use the same checkpoint identifier when resuming the message. A good choice for the checkpoint identifier would be the SHA1 hash of the message properties data (including the original filename, revised time, etc.). [WORK IN PROGRESS] This method resumes a reference from the last checkpoint. A reference is considered to be open (in scope) after a resume even though it will not have been opened via the open method during this session. The recipient MUST generate an error if the reference is currently open (in scope). [WORK IN PROGRESS] This method requests a specific quality of service. The QoS can be specified for the current channel or for all channels on the connection. The particular properties and semantics of a qos method always depend on the content class semantics. Though the qos method could in principle apply to both peers, it is currently meaningful only for the server. The client can request that messages be sent in advance so that when the client finishes processing a message, the following message is already held locally, rather than needing to be sent down the channel. Prefetching gives a performance improvement. This field specifies the prefetch window size in octets. The server will send a message in advance if it is equal to or smaller in size than the available prefetch size (and also falls into other prefetch limits). May be set to zero, meaning "no specific limit", although other prefetch limits may still apply. The prefetch-size is ignored if the no-ack option is set. The server MUST ignore this setting when the client is not processing any messages - i.e. the prefetch size does not limit the transfer of single messages to a client, only the sending in advance of more messages while the client still has one or more unacknowledged messages. Define a QoS prefetch-size limit and send a single message that exceeds that limit. Verify that the message arrives correctly. Specifies a prefetch window in terms of whole messages. This field may be used in combination with the prefetch-size field; a message will only be sent in advance if both prefetch windows (and those at the channel and connection level) allow it. The prefetch-count is ignored if the no-ack option is set. The server may send less data in advance than allowed by the client's specified prefetch windows but it MUST NOT send more. Define a QoS prefetch-size limit and a prefetch-count limit greater than one. Send multiple messages that exceed the prefetch size. Verify that no more than one message arrives at once. By default the QoS settings apply to the current channel only. If this field is set, they are applied to the entire connection. [WORK IN PROGRESS] Signals the normal completion of a method. [WORK IN PROGRESS] Signals that a queue does not contain any messages. [WORK IN PROGRESS] This response rejects a message. A message may be rejected for a number of reasons. [WORK IN PROGRESS] Returns the data offset into a reference body.