mirror of
https://github.com/Unidata/python-awips.git
synced 2025-02-23 14:57:56 -05:00
105 lines
4 KiB
Python
105 lines
4 KiB
Python
##
|
|
##
|
|
|
|
#
|
|
# Provides a Python-based interface for subscribing to qpid queues and topics.
|
|
#
|
|
#
|
|
#
|
|
# SOFTWARE HISTORY
|
|
#
|
|
# Date Ticket# Engineer Description
|
|
# ------------ ---------- ----------- --------------------------
|
|
# 11/17/10 njensen Initial Creation.
|
|
# 08/15/13 2169 bkowal Optionally gzip decompress any data that is read.
|
|
# 08/04/16 2416 tgurney Add queueStarted property
|
|
# 02/16/17 6084 bsteffen Support ssl connections
|
|
# 09/07/17 6175 tgurney Remove "decompressing" log message
|
|
#
|
|
#
|
|
|
|
import os
|
|
import os.path
|
|
import qpid
|
|
import zlib
|
|
|
|
from Queue import Empty
|
|
from qpid.exceptions import Closed
|
|
|
|
class QpidSubscriber:
|
|
|
|
def __init__(self, host='127.0.0.1', port=5672, decompress=False, ssl=None):
|
|
self.host = host
|
|
self.port = port
|
|
self.decompress = decompress;
|
|
socket = qpid.util.connect(host, port)
|
|
if "QPID_SSL_CERT_DB" in os.environ:
|
|
certdb = os.environ["QPID_SSL_CERT_DB"]
|
|
else:
|
|
certdb = os.path.expanduser("~/.qpid/")
|
|
if "QPID_SSL_CERT_NAME" in os.environ:
|
|
certname = os.environ["QPID_SSL_CERT_NAME"]
|
|
else:
|
|
certname = "guest"
|
|
certfile = os.path.join(certdb, certname + ".crt")
|
|
if ssl or (ssl is None and os.path.exists(certfile)):
|
|
keyfile = os.path.join(certdb, certname + ".key")
|
|
trustfile = os.path.join(certdb, "root.crt")
|
|
socket = qpid.util.ssl(socket, keyfile=keyfile, certfile=certfile, ca_certs=trustfile)
|
|
self.__connection = qpid.connection.Connection(sock=socket, username='guest', password='guest')
|
|
self.__connection.start()
|
|
self.__session = self.__connection.session(str(qpid.datatypes.uuid4()))
|
|
self.subscribed = True
|
|
self.__queueStarted = False
|
|
|
|
def topicSubscribe(self, topicName, callback):
|
|
# if the queue is edex.alerts, set decompress to true always for now to
|
|
# maintain compatibility with existing python scripts.
|
|
if (topicName == 'edex.alerts'):
|
|
self.decompress = True
|
|
|
|
print("Establishing connection to broker on", self.host)
|
|
queueName = topicName + self.__session.name
|
|
self.__session.queue_declare(queue=queueName, exclusive=True, auto_delete=True, arguments={'qpid.max_count':100, 'qpid.policy_type':'ring'})
|
|
self.__session.exchange_bind(exchange='amq.topic', queue=queueName, binding_key=topicName)
|
|
self.__innerSubscribe(queueName, callback)
|
|
|
|
def __innerSubscribe(self, serverQueueName, callback):
|
|
local_queue_name = 'local_queue_' + serverQueueName
|
|
queue = self.__session.incoming(local_queue_name)
|
|
self.__session.message_subscribe(serverQueueName, destination=local_queue_name)
|
|
queue.start()
|
|
print("Connection complete to broker on", self.host)
|
|
self.__queueStarted = True
|
|
|
|
while self.subscribed:
|
|
try:
|
|
message = queue.get(timeout=10)
|
|
content = message.body
|
|
self.__session.message_accept(qpid.datatypes.RangedSet(message.id))
|
|
if (self.decompress):
|
|
try:
|
|
# http://stackoverflow.com/questions/2423866/python-decompressing-gzip-chunk-by-chunk
|
|
d = zlib.decompressobj(16+zlib.MAX_WBITS)
|
|
content = d.decompress(content)
|
|
except Exception:
|
|
# decompression failed, return the original content
|
|
pass
|
|
callback(content)
|
|
except Empty:
|
|
pass
|
|
except Closed:
|
|
self.close()
|
|
|
|
def close(self):
|
|
self.__queueStarted = False
|
|
self.subscribed = False
|
|
try:
|
|
self.__session.close(timeout=10)
|
|
except Exception:
|
|
pass
|
|
|
|
@property
|
|
def queueStarted(self):
|
|
return self.__queueStarted
|
|
|