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<div class="docbook"><div class="navheader"><table summary="Navigation header" width="100%"><tr><th align="center" colspan="3">Appendix&#160;F.&#160;Impact of Broker enforced Producer Flow Control on Client</th></tr><tr><td align="left" width="20%"><a accesskey="p" href="JMS-Client-0-8-Appendix-Tomcat-JNDI-Integration.html">Prev</a>&#160;</td><th align="center" width="60%">&#160;</th><td align="right" width="20%">&#160;</td></tr></table><hr /></div><div class="appendix"><div class="titlepage"><div><div><h1 class="title"><a id="JMS-Client-0-8-Appendix-ProducerFlowControl-Impact"></a>Appendix&#160;F.&#160;Impact of Broker enforced Producer Flow Control on Client</h1></div></div></div><p>
Producing sessions can be blocked by the Qpid Broker when <span class="emphasis"><em>Producer Flow Control</em></span> is enforced
either on
<a class="link" href="../../java-broker/book/Java-Broker-Runtime-Disk-Space-Management.html#Java-Broker-Runtime-Disk-Space-Management-Producer-Flow-Control" target="_top">exceeding of disk quota</a>
or breaching of queue capacity when
<a class="link" href="../../java-broker/book/Java-Broker-Concepts-Queues.html#Java-Broker-Concepts-Queue-OverflowPolicy" target="_top">Producer Flow Control Overflow Policy</a>
is configured on queue.
</p><p>
If a producer sends to a queue which is overfull, the broker will respond by
instructing the client not to send any more messages. The impact of this is
that any future attempts to send will block until the broker rescinds the flow control order.
</p><p>
While blocking the client will periodically log the fact that it is blocked waiting on flow control.
</p><pre class="programlisting">
WARN Message send delayed by 5s due to broker enforced flow control
WARN Message send delayed by 10s due to broker enforced flow control
</pre><p>
After a set period the send will timeout and throw a JMSException to the calling code.
</p><p>
If such a JMSException is thrown, the message will not be sent to the broker,
however the underlying Session may still be active - in particular if the
Session is transactional then the current transaction will not be automatically
rolled back. Users may choose to either attempt to resend the message, or to
roll back any transactional work and close the Session.
</p><p>
Both the timeout delay and the periodicity of the warning messages can be set
using Java system properties.
</p><p>
The amount of time (in milliseconds) to wait before timing out
is controlled by the property qpid.flow_control_wait_failure.
</p><p>
The frequency at which the log message informing that the producer is flow
controlled is sent is controlled by the system property qpid.flow_control_wait_notify_period.
</p><p>
Adding the following to the command line to start the client would result in a timeout of one minute,
with warning messages every ten seconds:
</p><pre class="programlisting">
-Dqpid.flow_control_wait_failure=60000
-Dqpid.flow_control_wait_notify_period=10000
</pre></div><div class="navfooter"><hr /><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="JMS-Client-0-8-Appendix-Tomcat-JNDI-Integration.html">Prev</a>&#160;</td><td align="center" width="20%">&#160;</td><td align="right" width="40%">&#160;</td></tr><tr><td align="left" valign="top" width="40%">Appendix&#160;E.&#160;How to bind Qpid destinations and connection factories into Tomcat JNDI&#160;</td><td align="center" width="20%"><a accesskey="h" href="JMS-Client-Book.html">Home</a></td><td align="right" valign="top" width="40%">&#160;</td></tr></table></div></div>