<pclass="caption"><spanclass="caption-text">image</span><aclass="headerlink"href="#id3"title="Permalink to this image">¶</a></p>
</div>
<divclass="section"id="license">
<h2>License<aclass="headerlink"href="#license"title="Permalink to this headline">¶</a></h2>
<p>The AWIPS software package released by the Unidata Program Center is considered to
be in the public domain since it is released without proprietary code. As such, export
controls do not apply. Any person is free to download, modify, distribute, or share
Unidata AWIPS in any form. Entities who modify or re-distribute Unidata AWIPS
software are encouraged to conduct their own FOSS/COTS entitlement/license review
to ensure that they remain compatible with the associated terms (see
FOSS_COTS_License.pdf at <aclass="reference external"href="https://github.com/Unidata/awips2">https://github.com/Unidata/awips2</a>).</p>
</div>
<divclass="section"id="about-awips">
<h2>About AWIPS<aclass="headerlink"href="#about-awips"title="Permalink to this headline">¶</a></h2>
<p>The primary AWIPS application for data ingest, processing, and
storage is the Environmental Data EXchange (<strong>EDEX</strong>) server; the
primary AWIPS application for visualization/data manipulation is the
Common AWIPS Visualization Environment (<strong>CAVE</strong>) client, which is
typically installed on a workstation separate from other AWIPS
components.</p>
<p>In addition to programs developed specifically for AWIPS, AWIPS uses
several commercial off-the-shelf (COTS) and Free or Open Source software
(FOSS) products to assist in its operation. The following components,
working together and communicating, compose the entire AWIPS system.</p>
</div>
<divclass="section"id="edex">
<h2>EDEX<aclass="headerlink"href="#edex"title="Permalink to this headline">¶</a></h2>
<p>The main server for AWIPS. Qpid sends alerts to EDEX when data stored
by the LDM is ready for processing. These Qpid messages include file
header information which allows EDEX to determine the appropriate data
decoder to use. The default ingest server (simply named ingest) handles
all data ingest other than grib messages, which are processed by a
separate ingestGrib server. After decoding, EDEX writes metadata to the
database via Postgres and saves the processed data in HDF5 via PyPIES. A
third EDEX server, request, feeds requested data to CAVE clients. EDEX
ingest and request servers are started and stopped with the commands
<codeclass="docutils literal notranslate"><spanclass="pre">edex</span><spanclass="pre">start</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">edex</span><spanclass="pre">stop</span></code>, which runs the system script
<p>The <strong>LDM</strong> (Local Data Manager), developed and supported by Unidata, is
a suite of client and server programs designed for data distribution,
and is the fundamental component comprising the Unidata Internet Data
Distribution (IDD) system. In AWIPS, the LDM provides data feeds for
grids, surface observations, upper-air profiles, satellite and radar
imagery and various other meteorological datasets. The LDM writes data
directly to file and alerts EDEX via Qpid when a file is available for
processing. The LDM is started and stopped with the commands
<codeclass="docutils literal notranslate"><spanclass="pre">edex</span><spanclass="pre">start</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">edex</span><spanclass="pre">stop</span></code>, which runs the commands
<codeclass="docutils literal notranslate"><spanclass="pre">service</span><spanclass="pre">edex_ldm</span><spanclass="pre">start</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">service</span><spanclass="pre">edex_ldm</span><spanclass="pre">stop</span></code></p>
</div>
<divclass="section"id="edexbridge">
<h2>edexBridge<aclass="headerlink"href="#edexbridge"title="Permalink to this headline">¶</a></h2>
<p>edexBridge, invoked in the LDM configuration file
<codeclass="docutils literal notranslate"><spanclass="pre">/awips2/ldm/etc/ldmd.conf</span></code>, is used by the LDM to post “data
available” messaged to Qpid, which alerts the EDEX Ingest server that a
file is ready for processing.</p>
</div>
<divclass="section"id="id2">
<h2>Qpid<aclass="headerlink"href="#id2"title="Permalink to this headline">¶</a></h2>
<p><strong>Apache Qpid</strong>, the Queue Processor Interface Daemon, is the messaging
system used by AWIPS to facilitate communication between services.
When the LDM receives a data file to be processed, it employs
<strong>edexBridge</strong> to send EDEX ingest servers a message via Qpid. When EDEX
has finished decoding the file, it sends CAVE a message via Qpid that
data are available for display or further processing. Qpid is started
and stopped by <codeclass="docutils literal notranslate"><spanclass="pre">edex</span><spanclass="pre">start</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">edex</span><spanclass="pre">stop</span></code>, and is controlled by
the system script <codeclass="docutils literal notranslate"><spanclass="pre">/etc/rc.d/init.d/qpidd</span></code></p>
</div>
<divclass="section"id="postgresql">
<h2>PostgreSQL<aclass="headerlink"href="#postgresql"title="Permalink to this headline">¶</a></h2>
<p><strong>PostgreSQL</strong>, known simply as Postgres, is a relational database
management system (DBMS) which handles the storage and retrieval of
metadata, database tables and some decoded data. The storage and reading
of EDEX metadata is handled by the Postgres DBMS. Users may query the
metadata tables by using the termainal-based front-end for Postgres
called <strong>psql</strong>. Postgres is started and stopped by <codeclass="docutils literal notranslate"><spanclass="pre">edex</span><spanclass="pre">start</span></code> and
<codeclass="docutils literal notranslate"><spanclass="pre">edex</span><spanclass="pre">stop</span></code>, and is controlled by the system script
<h2>PyPIES (httpd-pypies)<aclass="headerlink"href="#pypies-httpd-pypies"title="Permalink to this headline">¶</a></h2>
<p><strong>PyPIES</strong>, Python Process Isolated Enhanced Storage, was created for
AWIPS to isolate the management of HDF5 Processed Data Storage from
the EDEX processes. PyPIES manages access, i.e., reads and writes, of
data in the HDF5 files. In a sense, PyPIES provides functionality
similar to a DBMS (i.e PostgreSQL for metadata); all data being written
to an HDF5 file is sent to PyPIES, and requests for data stored in HDF5
are processed by PyPIES.</p>
<p>PyPIES is implemented in two parts: 1. The PyPIES manager is a Python
application that runs as part of an Apache HTTP server, and handles
requests to store and retrieve data. 2. The PyPIES logger is a Python
process that coordinates logging. PyPIES is started and stopped by
<codeclass="docutils literal notranslate"><spanclass="pre">edex</span><spanclass="pre">start</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">edex</span><spanclass="pre">stop</span></code>, and is controlled by the system script
