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In order to protect + the Broker against malfunctioning (or malicious) client processes, it is possible to limit the + number of connections that can be active on any given port. + </p><p> + Connection limits on AMQP ports are controlled by an attribute "maxOpenConnections" on + the port. By default this takes the value of the context variable + <code class="literal">qpid.port.max_open_connections</code> which in itself is defaulted to the + value <code class="literal">-1</code> meaning there is no limit. + </p><p> + If the interpolated value of <code class="literal">maxOpenConnections</code> on an AMQP port is a + positive integer, then when that many active connections have been established no new + connections will be allowed (until an existing connection has been closed). Any such + rejection of a connection will be accompanied by the operational log message + <a class="link" href="Java-Broker-Appendix-Operation-Logging.html#Java-Broker-Appendix-Operation-Logging-Message-PRT-1005">PRT-1005</a>. + </p><p> + The context variable <code class="literal">qpid.port.open_connections_warn_percent</code> can be + used to control when a warning log message is generated as the number of open connections + approaches the limit for the port. The default value of this variable is + <code class="literal">80</code> meaning that if more the number of open connections to the port + has exceeded 80% of the given limit then the operatinal log message + <a class="link" href="Java-Broker-Appendix-Operation-Logging.html#Java-Broker-Appendix-Operation-Logging-Message-PRT-1004">PRT-1004</a> + will be generated. + </p></div><div class="navfooter"><hr /><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="Java-Broker-Runtime-Message-Compression.html">Prev</a> </td><td align="center" width="20%"><a accesskey="u" href="Java-Broker-Runtime.html">Up</a></td><td align="right" width="40%"> <a accesskey="n" href="Java-Broker-Runtime-Memory.html">Next</a></td></tr><tr><td align="left" valign="top" width="40%">9.8. Message Compression </td><td align="center" width="20%"><a accesskey="h" href="AMQP-Messaging-Broker-Java-Book.html">Home</a></td><td align="right" valign="top" width="40%"> 9.10. Memory</td></tr></table></div></div> + + <hr/> + + <ul id="-apache-navigation"> + <li><a href="http://www.apache.org/";>Apache</a></li> + <li><a href="http://www.apache.org/licenses/";>License</a></li> + <li><a href="http://www.apache.org/foundation/sponsorship.html";>Sponsorship</a></li> + <li><a href="http://www.apache.org/foundation/thanks.html";>Thanks!</a></li> + <li><a href="http://www.apache.org/security/";>Security</a></li> + <li><a href="http://www.apache.org/";><img id="-apache-feather" width="48" height="14" src="" alt="Apache"/></a></li> + </ul> + + <p id="-legal"> + Apache Qpid, Messaging built on AMQP; Copyright © 2015 + The Apache Software Foundation; Licensed under + the <a href="http://www.apache.org/licenses/LICENSE-2.0";>Apache + License, Version 2.0</a>; Apache Qpid, Qpid, Qpid Proton, + Proton, Apache, the Apache feather logo, and the Apache Qpid + project logo are trademarks of The Apache Software + Foundation; All other marks mentioned may be trademarks or + registered trademarks of their respective owners + </p> + </div> + </div> + </div> + </body> +</html>
http://git-wip-us.apache.org/repos/asf/qpid-site/blob/2069e43d/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Disk-Space-Management.html ---------------------------------------------------------------------- diff --git a/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Disk-Space-Management.html b/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Disk-Space-Management.html new file mode 100644 index 0000000..bf4873d --- /dev/null +++ b/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Disk-Space-Management.html @@ -0,0 +1,239 @@ +<!DOCTYPE html> +<!-- + - + - Licensed to the Apache Software Foundation (ASF) under one + - or more contributor license agreements. See the NOTICE file + - distributed with this work for additional information + - regarding copyright ownership. 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See the License for the + - specific language governing permissions and limitations + - under the License. + - +--> +<html xmlns="http://www.w3.org/1999/xhtml"; xml:lang="en"> + <head> + <title>9.2. Disk Space Management - Apache Qpid™</title> + <meta http-equiv="X-UA-Compatible" content="IE=edge"/> + <meta name="viewport" content="width=device-width, initial-scale=1.0"/> + <link rel="stylesheet" href="/site.css" type="text/css" async="async"/> + <link rel="stylesheet" href="/deferred.css" type="text/css" defer="defer"/> + <script type="text/javascript">var _deferredFunctions = [];</script> + <script type="text/javascript" src="/deferred.js" defer="defer"></script> + <!--[if lte IE 8]> + <link rel="stylesheet" href="/ie.css" type="text/css"/> + <script type="text/javascript" src="/html5shiv.js"></script> + <![endif]--> + + <!-- Redirects for `go get` and godoc.org --> + <meta name="go-import" + content="qpid.apache.org git https://git-wip-us.apache.org/repos/asf/qpid-proton.git"/> + <meta name="go-source" + content="qpid.apache.org +https://github.com/apache/qpid-proton/blob/go1/README.md +https://github.com/apache/qpid-proton/tree/go1{/dir} +https://github.com/apache/qpid-proton/blob/go1{/dir}/{file}#L{line}"/> + </head> + <body> + <div id="-content"> + <div id="-top" class="panel"> + <a id="-menu-link"><img width="16" height="16" src="" alt="Menu"/></a> + + <a id="-search-link"><img width="22" height="16" src="" alt="Search"/></a> + + <ul id="-global-navigation"> + <li><a id="-logotype" href="/index.html">Apache Qpid<sup>™</sup></a></li> + <li><a href="/documentation.html">Documentation</a></li> + <li><a href="/download.html">Download</a></li> + <li><a href="/discussion.html">Discussion</a></li> + </ul> + </div> + + <div id="-menu" class="panel" style="display: none;"> + <div class="flex"> + <section> + <h3>Project</h3> + + <ul> + <li><a href="/overview.html">Overview</a></li> + <li><a href="/components/index.html">Components</a></li> + <li><a href="/releases/index.html">Releases</a></li> + </ul> + </section> + + <section> + <h3>Messaging APIs</h3> + + <ul> + <li><a href="/proton/index.html">Qpid Proton</a></li> + <li><a href="/components/jms/index.html">Qpid JMS</a></li> + <li><a href="/components/messaging-api/index.html">Qpid Messaging API</a></li> + </ul> + </section> + + <section> + <h3>Servers and tools</h3> + + <ul> + <li><a href="/components/java-broker/index.html">Java broker</a></li> + <li><a href="/components/cpp-broker/index.html">C++ broker</a></li> + <li><a href="/components/dispatch-router/index.html">Dispatch router</a></li> + </ul> + </section> + + <section> + <h3>Resources</h3> + + <ul> + <li><a href="/dashboard.html">Dashboard</a></li> + <li><a href="https://cwiki.apache.org/confluence/display/qpid/Index";>Wiki</a></li> + <li><a href="/resources.html">More resources</a></li> + </ul> + </section> + </div> + </div> + + <div id="-search" class="panel" style="display: none;"> + <form action="http://www.google.com/search"; method="get"> + <input type="hidden" name="sitesearch" value="qpid.apache.org"/> + <input type="text" name="q" maxlength="255" autofocus="autofocus" tabindex="1"/> + <button type="submit">Search</button> + <a href="/search.html">More ways to search</a> + </form> + </div> + + <div id="-middle" class="panel"> + <ul id="-path-navigation"><li><a href="/index.html">Home</a></li><li><a href="/releases/index.html">Releases</a></li><li><a href="/releases/qpid-java-6.0.3/index.html">Qpid Java 6.0.3</a></li><li><a href="/releases/qpid-java-6.0.3/java-broker/book/index.html">AMQP Messaging Broker (Java)</a></li><li>9.2. Disk Space Management</li></ul> + + <div id="-middle-content"> + <div class="docbook"><div class="navheader"><table summary="Navigation header" width="100%"><tr><th align="center" colspan="3">9.2. Disk Space Management</th></tr><tr><td align="left" width="20%"><a accesskey="p" href="Java-Broker-Runtime.html">Prev</a> </td><th align="center" width="60%">Chapter 9. Runtime</th><td align="right" width="20%"> <a accesskey="n" href="Java-Broker-Runtime-Producer-Transaction-Timeout.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Java-Broker-Runtime-Disk-Space-Management"></a>9.2. Disk Space Management</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="Qpid-Producer-Flow-Control"></a>9.2.1. Producer Flow Control</h3></div></div></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="Java-Broker-Runtime-Disk-Space-Management-Producer-Flow- Control-GeneralInformation"></a>9.2.1.1. General Information</h4></div></div></div><p> + The Java Broker supports a flow control mechanism to which can be used to prevent either a single queue + or a virtualhost exceeding configured limits. These two mechanisms are described + next. + </p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="Java-Broker-Runtime-Disk-Space-Management-Producer-Flow-Control-ServerConfiguration"></a>9.2.1.2. Server Configuration</h4></div></div></div><div class="section"><div class="titlepage"><div><div><h5 class="title"><a id="d0e5343"></a>Configuring a Queue to use flow control</h5></div></div></div><p> + Flow control is enabled on a producer when it sends a message to a Queue + which is "overfull". The producer flow control will be rescinded when all + Queues on which a producer is blocking become "underfull". A Queue is defined + as overfull when the size (in bytes) of the messages on the queue exceeds the + <span class="emphasis"><em>capacity</em></span> of the Queue. A Queue becomes "underfull" when its + size becomes less than the <span class="emphasis"><em>resume capacity</em></span>. + </p><p> + The capacity and resume capacity can be specified when the queue is created. This + can be done using the Flow Control Settings within the Queue creation dialogue. + </p><div class="section"><div class="titlepage"><div><div><h6 class="title"><a id="d0e5356"></a>Broker Log Messages</h6></div></div></div><p> + There are four Broker log messages that may occur if flow control through queue capacity limits is enabled. + Firstly, when a capacity limited queue becomes overfull, a log message similar to the following is produced + </p><pre class="programlisting"> +MESSAGE [vh(/test)/qu(MyQueue)] [vh(/test)/qu(MyQueue)] QUE-1003 : Overfull : Size : 1,200 bytes, Capacity : 1,000 + </pre><p>Then for each channel which becomes blocked upon the overful queue a log message similar to the following is produced:</p><pre class="programlisting"> +MESSAGE [con:2(guest@anonymous(713889609)/test)/ch:1] [con:2(guest@anonymous(713889609)/test)/ch:1] CHN-1005 : Flow Control Enforced (Queue MyQueue) + </pre><p>When enough messages have been consumed from the queue that it becomes underfull, then the following log is generated: </p><pre class="programlisting"> +MESSAGE [vh(/test)/qu(MyQueue)] [vh(/test)/qu(MyQueue)] QUE-1004 : Underfull : Size : 600 bytes, Resume Capacity : 800 + </pre><p>And for every channel which becomes unblocked you will see a message similar to: </p><pre class="programlisting"> +MESSAGE [con:2(guest@anonymous(713889609)/test)/ch:1] [con:2(guest@anonymous(713889609)/test)/ch:1] CHN-1006 : Flow Control Removed + </pre><p>Obviously the details of connection, virtual host, queue, size, capacity, etc would depend on the configuration in use.</p></div></div><div class="section"><div class="titlepage"><div><div><h5 class="title"><a id="d0e5379"></a>Disk quota-based flow control</h5></div></div></div><p> + Flow control can also be triggered when a configured disk quota is exceeded. This is supported by the BDB and + Derby virtualhosts. + </p><p> + This functionality blocks all producers on reaching the disk overflow limit. When consumers + consume the messages, causing disk space usage to falls below the underflow limit, the + producers are unblocked and continue working as normal. + </p><p> + Two limits can be configured: + </p><p> + overfull limit - the maximum space on disk (in bytes). + </p><p> + underfull limit - when the space on disk drops below this limit, producers are allowed to resume publishing. + </p><p> + The overfull and underful limit can be specified when a new virtualhost is created or an exiting + virtualhost is edited. This can be done using the Store Overflow and Store Underfull settings + within the virtual host creation and edit dialogue. If editing an existing virtualhost, the virtualhost + must be restarted for the new values to take effect. + </p><p> + The disk quota functionality is based on "best effort" principle. This means the broker + cannot guarantee that the disk space limit will not be exceeded. If several concurrent + transactions are started before the limit is reached, which collectively cause the limit + to be exceeded, the broker may allow all of them to be committed. + </p><p> + The Broker will also impose flow control if the filesystem hosting a virtualhost + exceeds a <a class="link" href="Java-Broker-Management-Managing-Broker.html#Java-Broker-Management-Managing-Broker-Context-StoreFilesystemMaxUsagePercent"> + configured percentage.</a>. + </p><div class="section"><div class="titlepage"><div><div><h6 class="title"><a id="d0e5401"></a>Broker Log Messages for quota flow control</h6></div></div></div><p> + There are two broker log messages that may occur if flow control through disk quota limits is enabled. + When the virtual host is blocked due to exceeding of the disk quota limit the following message + appears in the broker log + </p><pre class="programlisting"> +[vh(/test)/ms(BDBMessageStore)] MST-1008 : Store overfull, flow control will be enforced + </pre><p> + When virtual host is unblocked after cleaning the disk space the following message appears in the broker log + </p><pre class="programlisting"> +[vh(/test)/ms(BDBMessageStore)] MST-1009 : Store overfull condition cleared + </pre><p> + </p></div></div></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="Java-Broker-Runtime-Disk-Space-Management-Producer-Flow-Control-ClientImpact"></a>9.2.1.3. Client impact and configuration</h4></div></div></div><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></div><div class="navfooter"><hr /><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="Java-Broker-Runtime.html">Prev</a> </td><td align="center" width="20%"><a accesskey="u" href="Java-Broker-Runtime.html">Up</a></td><td align="right" width="40%"> <a accesskey="n" href="Java-Broker-Runtime-Producer-Transaction-Timeout.html">Next</a></td></tr><tr><td align="left" valign="top" width="40%">Chapter 9. Runtime </td><td align="center" width="20%"><a accesskey="h" href="AMQP-Messaging-Broker-Java-Book.html">Home</a></td><td align="right" valign="top" width="40%"> 9.3. Producer Transaction Timeout</td></tr></table></div></div> + + <hr/> + + <ul id="-apache-navigation"> + <li><a href="http://www.apache.org/";>Apache</a></li> + <li><a href="http://www.apache.org/licenses/";>License</a></li> + <li><a href="http://www.apache.org/foundation/sponsorship.html";>Sponsorship</a></li> + <li><a href="http://www.apache.org/foundation/thanks.html";>Thanks!</a></li> + <li><a href="http://www.apache.org/security/";>Security</a></li> + <li><a href="http://www.apache.org/";><img id="-apache-feather" width="48" height="14" src="" alt="Apache"/></a></li> + </ul> + + <p id="-legal"> + Apache Qpid, Messaging built on AMQP; Copyright © 2015 + The Apache Software Foundation; Licensed under + the <a href="http://www.apache.org/licenses/LICENSE-2.0";>Apache + License, Version 2.0</a>; Apache Qpid, Qpid, Qpid Proton, + Proton, Apache, the Apache feather logo, and the Apache Qpid + project logo are trademarks of The Apache Software + Foundation; All other marks mentioned may be trademarks or + registered trademarks of their respective owners + </p> + </div> + </div> + </div> + </body> +</html> http://git-wip-us.apache.org/repos/asf/qpid-site/blob/2069e43d/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Flow-To-Disk.html ---------------------------------------------------------------------- diff --git a/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Flow-To-Disk.html b/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Flow-To-Disk.html new file mode 100644 index 0000000..61931a8 --- /dev/null +++ b/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Flow-To-Disk.html @@ -0,0 +1,159 @@ +<!DOCTYPE html> +<!-- + - + - Licensed to the Apache Software Foundation (ASF) under one + - or more contributor license agreements. 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Once this + limit is reached any new transient messages and all existing transient messages will be + transferred to disk. Newly arriving transient messages will continue to go to the disk until the + cumulative size of all messages falls below the limit once again.</p><p>By default the Broker makes 40% of the max direct available memory for messages. This memory is + divided between all the queues across all virtual hosts defined on the Broker with a percentage + calculated according to their current queue size. These calculations are refreshed periodically + by the housekeeping cycle.</p><p>For example if there are two queues, one containing 75MB and the second 100MB messages + respectively and the Broker has 1GB direct memory with the default of 40% available for messages. + The first queue will have a target size of 170MB and the second 230MB. Once 400MB is taken by + messages, messages will begin to flow to disk. New messages will cease to flow to disk when + their cumulative size falls beneath 400MB.</p><p>Flow to disk is configured by Broker context variable + <code class="literal">broker.flowToDiskThreshold</code>. It is expressed as a size in bytes and defaults + to 40% of the JVM maximum heap size.</p><p>Log message <a class="link" href="Java-Broker-Appendix-Operation-Logging.html#Java-Broker-Appendix-Operation-Logging-Message-BRK-1014">BRK-1014</a> is written when the feature activates. Once the total space of all messages + decreases below the threshold, the message <a class="link" href="Java-Broker-Appendix-Operation-Logging.html#Java-Broker-Appendix-Operation-Logging-Message-BRK-1015">BRK-1015</a> is written + to show that the feature is no longer active.</p></div><div class="navfooter"><hr /><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="Java-Broker-Runtime-Close-Connection-When-No-Route.html">Prev</a> </td><td align="center" width="20%"><a accesskey="u" href="Java-Broker-Runtime.html">Up</a></td><td align="right" width="40%"> <a accesskey="n" href="Java-Broker-Runtime-Background-Recovery.html">Next</a></td></tr><tr><td align="left" valign="top" width="40%">9.5. Closing client connections on unroutable mandatory messages </td><td align="center" width="20%"><a accesskey="h" href="AMQP-Messaging-Broker-Java-Book.html">Home</a></td><td align="right" valign="top" width="40%"> 9.7. Background Recovery</td></tr></table></div></div> + + <hr/> + + <ul id="-apache-navigation"> + <li><a href="http://www.apache.org/";>Apache</a></li> + <li><a href="http://www.apache.org/licenses/";>License</a></li> + <li><a href="http://www.apache.org/foundation/sponsorship.html";>Sponsorship</a></li> + <li><a href="http://www.apache.org/foundation/thanks.html";>Thanks!</a></li> + <li><a href="http://www.apache.org/security/";>Security</a></li> + <li><a href="http://www.apache.org/";><img id="-apache-feather" width="48" height="14" src="" alt="Apache"/></a></li> + </ul> + + <p id="-legal"> + Apache Qpid, Messaging built on AMQP; Copyright © 2015 + The Apache Software Foundation; Licensed under + the <a href="http://www.apache.org/licenses/LICENSE-2.0";>Apache + License, Version 2.0</a>; Apache Qpid, Qpid, Qpid Proton, + Proton, Apache, the Apache feather logo, and the Apache Qpid + project logo are trademarks of The Apache Software + Foundation; All other marks mentioned may be trademarks or + registered trademarks of their respective owners + </p> + </div> + </div> + </div> + </body> +</html> http://git-wip-us.apache.org/repos/asf/qpid-site/blob/2069e43d/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Handling-Undeliverable-Messages.html ---------------------------------------------------------------------- diff --git a/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Handling-Undeliverable-Messages.html b/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Handling-Undeliverable-Messages.html new file mode 100644 index 0000000..e7f5031 --- /dev/null +++ b/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Handling-Undeliverable-Messages.html @@ -0,0 +1,182 @@ +<!DOCTYPE html> +<!-- + - + - Licensed to the Apache Software Foundation (ASF) under one + - or more contributor license agreements. 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See the License for the + - specific language governing permissions and limitations + - under the License. + - +--> +<html xmlns="http://www.w3.org/1999/xhtml"; xml:lang="en"> + <head> + <title>9.4. Handing Undeliverable Messages - Apache Qpid™</title> + <meta http-equiv="X-UA-Compatible" content="IE=edge"/> + <meta name="viewport" content="width=device-width, initial-scale=1.0"/> + <link rel="stylesheet" href="/site.css" type="text/css" async="async"/> + <link rel="stylesheet" href="/deferred.css" type="text/css" defer="defer"/> + <script type="text/javascript">var _deferredFunctions = [];</script> + <script type="text/javascript" src="/deferred.js" defer="defer"></script> + <!--[if lte IE 8]> + <link rel="stylesheet" href="/ie.css" type="text/css"/> + <script type="text/javascript" src="/html5shiv.js"></script> + <![endif]--> + + <!-- Redirects for `go get` and godoc.org --> + <meta name="go-import" + content="qpid.apache.org git https://git-wip-us.apache.org/repos/asf/qpid-proton.git"/> + <meta name="go-source" + content="qpid.apache.org +https://github.com/apache/qpid-proton/blob/go1/README.md +https://github.com/apache/qpid-proton/tree/go1{/dir} +https://github.com/apache/qpid-proton/blob/go1{/dir}/{file}#L{line}"/> + </head> + <body> + <div id="-content"> + <div id="-top" class="panel"> + <a id="-menu-link"><img width="16" height="16" src="" alt="Menu"/></a> + + <a id="-search-link"><img width="22" height="16" src="" alt="Search"/></a> + + <ul id="-global-navigation"> + <li><a id="-logotype" href="/index.html">Apache Qpid<sup>™</sup></a></li> + <li><a href="/documentation.html">Documentation</a></li> + <li><a href="/download.html">Download</a></li> + <li><a href="/discussion.html">Discussion</a></li> + </ul> + </div> + + <div id="-menu" class="panel" style="display: none;"> + <div class="flex"> + <section> + <h3>Project</h3> + + <ul> + <li><a href="/overview.html">Overview</a></li> + <li><a href="/components/index.html">Components</a></li> + <li><a href="/releases/index.html">Releases</a></li> + </ul> + </section> + + <section> + <h3>Messaging APIs</h3> + + <ul> + <li><a href="/proton/index.html">Qpid Proton</a></li> + <li><a href="/components/jms/index.html">Qpid JMS</a></li> + <li><a href="/components/messaging-api/index.html">Qpid Messaging API</a></li> + </ul> + </section> + + <section> + <h3>Servers and tools</h3> + + <ul> + <li><a href="/components/java-broker/index.html">Java broker</a></li> + <li><a href="/components/cpp-broker/index.html">C++ broker</a></li> + <li><a href="/components/dispatch-router/index.html">Dispatch router</a></li> + </ul> + </section> + + <section> + <h3>Resources</h3> + + <ul> + <li><a href="/dashboard.html">Dashboard</a></li> + <li><a href="https://cwiki.apache.org/confluence/display/qpid/Index";>Wiki</a></li> + <li><a href="/resources.html">More resources</a></li> + </ul> + </section> + </div> + </div> + + <div id="-search" class="panel" style="display: none;"> + <form action="http://www.google.com/search"; method="get"> + <input type="hidden" name="sitesearch" value="qpid.apache.org"/> + <input type="text" name="q" maxlength="255" autofocus="autofocus" tabindex="1"/> + <button type="submit">Search</button> + <a href="/search.html">More ways to search</a> + </form> + </div> + + <div id="-middle" class="panel"> + <ul id="-path-navigation"><li><a href="/index.html">Home</a></li><li><a href="/releases/index.html">Releases</a></li><li><a href="/releases/qpid-java-6.0.3/index.html">Qpid Java 6.0.3</a></li><li><a href="/releases/qpid-java-6.0.3/java-broker/book/index.html">AMQP Messaging Broker (Java)</a></li><li>9.4. Handing Undeliverable Messages</li></ul> + + <div id="-middle-content"> + <div class="docbook"><div class="navheader"><table summary="Navigation header" width="100%"><tr><th align="center" colspan="3">9.4. Handing Undeliverable Messages</th></tr><tr><td align="left" width="20%"><a accesskey="p" href="Java-Broker-Runtime-Producer-Transaction-Timeout.html">Prev</a> </td><th align="center" width="60%">Chapter 9. Runtime</th><td align="right" width="20%"> <a accesskey="n" href="Java-Broker-Runtime-Close-Connection-When-No-Route.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Java-Broker-Runtime-Handling-Undeliverable-Messages"></a>9.4. Handing Undeliverable Messages</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="Java-Broker-Runtime-Handling-Undeliverable-Messages-Introduction"></a>9.4.1. Introduction</h3></div></div></div><p> Messages that cannot be delivered successfu lly to a consumer (for instance, because the + client is using a transacted session and rolls-back the transaction) can be made available on + the queue again and then subsequently be redelivered, depending on the precise session + acknowledgement mode and messaging model used by the application. This is normally desirable + behaviour that contributes to the ability of a system to withstand unexpected errors. However, it + leaves open the possibility for a message to be repeatedly redelivered (potentially indefinitely), + consuming system resources and preventing the delivery of other messages. Such undeliverable + messages are sometimes known as poison messages.</p><p>For an example, consider a stock ticker application that has been designed to consume prices + contained within JMS TextMessages. What if inadvertently a BytesMessage is placed onto the queue? + As the ticker application does not expect the BytesMessage, its processing might fail and cause it + to roll-back the transaction, however the default behavior of the Broker would mean that the + BytesMessage would be delivered over and over again, preventing the delivery of other legitimate + messages, until an operator intervenes and removes the erroneous message from the queue. </p><p>Qpid has maximum delivery count and dead-letter queue (DLQ) features which can be used in + concert to construct a system that automatically handles such a condition. These features are + described in the following sections.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="Java-Broker-Runtime-Handling-Undeliverable-Messages-Maximum-Delivery-Count"></a>9.4.2. Maximum Delivery Count</h3></div></div></div><p> Maximum delivery count is a property of a queue. If a consumer application is unable to + process a message more than the specified number of times, then the broker will either route the + message to a dead-letter queue (if one has been defined), or will discard the message. </p><p> In order for a maximum delivery count to be enforced, the consuming client + <span class="emphasis"><em>must</em></span> call <a class="link" href="http://docs.oracle.com/javaee/6/api/javax/jms/Session.html#rollback()" target="_top">Session#rollback()</a> (or <a class="link" href="http://docs.oracle.com/javaee/6/api/javax/jms/Session.html#recover()" target="_top">Session#recover()</a> if the session is not transacted). It is during the Broker's + processing of Session#rollback() (or Session#recover()) that if a message has been seen + at least the maximum number of times then it will move the message to the DLQ or discard the + message.</p><p>If the consuming client fails in another manner, for instance, closes the connection, the + message will not be re-routed and consumer application will see the same poison message again + once it reconnects.</p><p> If the consuming application is using AMQP 0-9-1, 0-9, or 0-8 protocols, it is necessary to + set the client system property <code class="varname">qpid.reject.behaviour</code> or connection or binding + URL option <code class="varname">rejectbehaviour</code> to the value <code class="literal">server</code>.</p><p>It is possible to determine the number of times a message has been sent to a consumer via + the Management interfaces, but is not possible to determine this information from a message client. + Specifically, the optional JMS message header <span class="property">JMSXDeliveryCount</span> is not + supported.</p><p>Maximum Delivery Count can be specified when a new queue is created or using the the + queue declare property <span class="property">x-qpid-maximum-delivery-count</span></p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="Java-Broker-Runtime-Handling-Undeliverable-Messages-Dead-Letter-Queues"></a>9.4.3. Dead Letter Queues (DLQ)</h3></div></div></div><p>A Dead Letter Queue (DLQ) acts as an destination for messages that have somehow exceeded the + normal bounds of processing and is utilised to prevent disruption to flow of other messages. When + a DLQ is enabled for a given queue if a consuming client indicates it no longer wishes the + receive the message (typically by exceeding a Maximum Delivery Count) then the message is moved + onto the DLQ and removed from the original queue. </p><p>The DLQ feature causes generation of a Dead Letter Exchange and a Dead Letter Queue. These + are named convention QueueName<span class="emphasis"><em>_DLE</em></span> and QueueName<span class="emphasis"><em>_DLQ</em></span>.</p><p>DLQs can be enabled when a new queue is created + or using the queue declare property <span class="property">x-qpid-dlq-enabled</span>.</p><div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Avoid excessive queue depth</h3><p>Applications making use of DLQs <span class="emphasis"><em>should</em></span> make provision for the frequent + examination of messages arriving on DLQs so that both corrective actions can be taken to resolve + the underlying cause and organise for their timely removal from the DLQ. Messages on DLQs + consume system resources in the same manner as messages on normal queues so excessive queue + depths should not be permitted to develop.</p></div></div></div><div class="navfooter"><hr /><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="Java-Broker-Runtime-Producer-Transaction-Timeout.html">Prev</a> </td><td align="center" width="20%"><a accesskey="u" href="Java-Broker-Runtime.html">Up</a></td><td align="right" width="40%"> <a accesskey="n" href="Java-Broker-Runtime-Close-Connection-When-No-Route.html">Next</a></td></tr><tr><td align="left" valign="top" width="40%">9.3. Producer Transaction Timeout </td><td align="center" width="20%"><a accesskey="h" href="AMQP-Messaging-Broker-Java-Book.html">Home</a></td><td align="right" valign="top" width="40%"> 9.5. Closing client connections on unroutable mandatory messages</td></tr></table></div></div> + + <hr/> + + <ul id="-apache-navigation"> + <li><a href="http://www.apache.org/";>Apache</a></li> + <li><a href="http://www.apache.org/licenses/";>License</a></li> + <li><a href="http://www.apache.org/foundation/sponsorship.html";>Sponsorship</a></li> + <li><a href="http://www.apache.org/foundation/thanks.html";>Thanks!</a></li> + <li><a href="http://www.apache.org/security/";>Security</a></li> + <li><a href="http://www.apache.org/";><img id="-apache-feather" width="48" height="14" src="" alt="Apache"/></a></li> + </ul> + + <p id="-legal"> + Apache Qpid, Messaging built on AMQP; Copyright © 2015 + The Apache Software Foundation; Licensed under + the <a href="http://www.apache.org/licenses/LICENSE-2.0";>Apache + License, Version 2.0</a>; Apache Qpid, Qpid, Qpid Proton, + Proton, Apache, the Apache feather logo, and the Apache Qpid + project logo are trademarks of The Apache Software + Foundation; All other marks mentioned may be trademarks or + registered trademarks of their respective owners + </p> + </div> + </div> + </div> + </body> +</html> http://git-wip-us.apache.org/repos/asf/qpid-site/blob/2069e43d/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Memory.html ---------------------------------------------------------------------- diff --git a/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Memory.html b/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Memory.html new file mode 100644 index 0000000..f8fa191 --- /dev/null +++ b/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Memory.html @@ -0,0 +1,266 @@ +<!DOCTYPE html> +<!-- + - + - Licensed to the Apache Software Foundation (ASF) under one + - or more contributor license agreements. 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width="60%">Chapter 9. Runtime</th><td align="right" width="20%"> <a accesskey="n" href="Java-Broker-High-Availability.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Java-Broker-Runtime-Memory"></a>9.10. Memory</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="Java-Broker-Runtime-Memory-Introduction"></a>9.10.1. Introduction</h3></div></div></div><p> + Understanding how the Qpid broker uses memory is essential to running a high performing and reliable service. + A wrongly configured broker can exhibit poor performance or even crash with an <code class="literal">OutOfMemoryError</code>. + Unfortunately, memory usage is not a simple topic and thus requires some in depth explanations. + This page should give the required background information to make informed decisions on how to configure your broker. + </p><p> + <a class="xref" href="Java-Broker-Runtime-Memory.html#Java-Broker-Runtime-Memory-Types" title="9.10.2. Types of Memory">Section 9.10.2, “Types of Memory”</a> explains the two different kinds of Java memory most relevant to the broker. + <a class="xref" href="Java-Broker-Runtime-Memory.html#Java-Broker-Runtime-Memory-Usage" title="9.10.3. Memory Usage in the Broker">Section 9.10.3, “Memory Usage in the Broker”</a> goes on to explain which parts of the broker use what kind of memory. + <a class="xref" href="Java-Broker-Runtime-Memory.html#Java-Broker-Runtime-Memory-Low-Memory" title="9.10.4. Low Memory Conditions">Section 9.10.4, “Low Memory Conditions”</a> explains what happens when the system runs low on memory. + <a class="xref" href="Java-Broker-Runtime-Memory.html#Java-Broker-Runtime-Memory-Defaults" title="9.10.5. Defaults">Section 9.10.5, “Defaults”</a> lays out the default settings of the Qpid broker. + Finally, <a class="xref" href="Java-Broker-Runtime-Memory.html#Java-Broker-Runtime-Memory-Tuning" title="9.10.6. Memory Tuning the Broker">Section 9.10.6, “Memory Tuning the Broker”</a> gives some advice on tuning your broker. + </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="Java-Broker-Runtime-Memory-Types"></a>9.10.2. Types of Memory</h3></div></div></div><p> + While Java has a couple of different internal memory types we will focus on the two types that are relevant to the Qpid broker. + Both of these memory types are taken from the same physical memory (RAM). + </p><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="d0e5806"></a>9.10.2.1. Heap</h4></div></div></div><p> + Normally, all objects are allocated from Java's heap memory. + Once, nothing references an object it is cleaned up by the Java Garbage Collector and it's memory returned to the heap. + This works fine for most use cases. + However, when interacting with other parts of the operating system using Java's heap is not ideal. + This is where the so called direct memory comes into play. + </p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="d0e5811"></a>9.10.2.2. Direct</h4></div></div></div><p> + The world ouside of the JVM, in particular the operating system (OS), does not know about Java heap memory and uses other structures like C arrays. + In order to interact with these systems Java needs to copy data between its own heap memory and these native structures. + This can become a bottle neck when there is a lot of exchange between Java and the OS like in I/O (both disk and network) heavy applications. + Java's solution to this is to allow programmers to request <code class="literal">ByteBuffer</code>s from so called direct memory. + This is an opaque structure that <span class="emphasis"><em>might</em></span> have an underlying implementation that makes it efficient to interact with the OS. + Unfortunately, the GC is not good at tracking direct memory and in general it is inadvisable to use direct memory for regular objects. + </p></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="Java-Broker-Runtime-Memory-Usage"></a>9.10.3. Memory Usage in the Broker</h3></div></div></div><p> + This section lists some note worthy users of memory within the broker and where possible lists their usage of heap and direct memory. + Note that to ensure smooth performance some heap memory should remain unused by the application and be reserved for the JVM to do house keeping and garbage collection. + <a class="link" href="https://docs.oracle.com/cd/E17277_02/html/java/com/sleepycat/je/util/DbCacheSize.html"; target="_top">Some guides</a> advise to reserve up to 30% of heap memory for the JVM. + </p><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="d0e5830"></a>9.10.3.1. Broker</h4></div></div></div><p> + The broker itself uses a moderate amount of heap memory (≈15 MB). + However, each connection and session comes with a heap overhead of about 17 kB and 15 kB respectively. + In addition, each connection reserves 512 kB direct memory for network I/O. + </p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="d0e5835"></a>9.10.3.2. Virtual Hosts</h4></div></div></div><p> + The amount of memory a Virtual Host uses depends on its type. + For a JSON Virtual Host Node with a BDB Virtual Host the heap memory usage is approximately 2 MB. + However, each BDB Virtual Hosts has a mandatory cache in heap memory which has an impact on performance. + See <a class="link" href="Java-Broker-Runtime-Memory.html#Java-Broker-Runtime-Memory-Usage-BDB" title="9.10.3.4. Message Store">below</a> for more information. + </p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="d0e5843"></a>9.10.3.3. Messages</h4></div></div></div><p> + Messages and their headers are kept in direct memory and have an additional overhead of approximately 1 kB heap memory each. + This means that most brokers will want to have more direct memory than heap memory. + When many small messages accumulate on the broker the 1 kB heap memory overhead can become a <a class="link" href="Java-Broker-Runtime-Memory.html#Java-Broker-Runtime-Memory-Low-Memory-Heap" title="9.10.4.1. Low on Heap Memory">limiting factor</a>. + </p><p> + When the broker is <a class="link" href="Java-Broker-Runtime-Memory.html#Java-Broker-Runtime-Memory-Low-Memory-Direct" title="9.10.4.2. Low on Direct Memory">running low on direct memory</a> + it will evict messages from memory and <a class="link" href="Java-Broker-Runtime-Flow-To-Disk.html" title="9.6. Flow to Disk">flow them to disk</a>. + For persistent messages this only means freeing the direct memory representation because they always have an on-disk representation to guard against unexpected failure (e.g., a power cut). + For transient messages this implies additional disk I/O. + After being flown to disk messages need to be re-read from disk before delivery. + </p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="Java-Broker-Runtime-Memory-Usage-BDB"></a>9.10.3.4. Message Store</h4></div></div></div><div class="section"><div class="titlepage"><div><div><h5 class="title"><a id="d0e5862"></a>Berkeley DB (BDB)</h5></div></div></div><p> + The broker can use Oracle's BDB JE (BDB) as a message store to persist messages by writing them to a database. + BDB uses a mandatory cache for navigating and organising its database structure. + Sizing and tuning this cache is a topic of its own and would go beyond the scope of this guide. + Suffice to say that by default Qpid uses 5% of heap memory for BDB caches (each Virtual Host uses a separate cache) or 10 MB per BDB store, whichever is greater. + See the <a class="link" href="http://www.oracle.com/us/products/database/berkeley-db/je"; target="_top">official webpage</a> especially <a class="link" href="http://docs.oracle.com/cd/E17277_02/html/java/com/sleepycat/je/util/DbCacheSize.html"; target="_top">this page</a> for more information. + For those interested, Qpid uses <a class="link" href="http://docs.oracle.com/cd/E17277_02/html/java/com/sleepycat/je/CacheMode.html#EVICT_LN"; target="_top">EVICT_LN</a> as its default JE cacheMode. + </p><p> + Note that due to licensing concerns Qpid does not ship the BDB JE jar files. + </p></div><div class="section"><div class="titlepage"><div><div><h5 class="title"><a id="d0e5878"></a>Derby</h5></div></div></div><p> + TODO + </p></div></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="d0e5883"></a>9.10.3.5. HTTP Management</h4></div></div></div><p> + Qpid uses Jetty for the HTTP Management (both REST and Web Management Console). + When the management plugin is loaded it will allocate the memory it needs and should not require more memory during operation and can thus be largely ignored. + </p></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="Java-Broker-Runtime-Memory-Low-Memory"></a>9.10.4. Low Memory Conditions</h3></div></div></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="Java-Broker-Runtime-Memory-Low-Memory-Heap"></a>9.10.4.1. Low on Heap Memory</h4></div></div></div><p> + When the broker runs low on heap memory performance will degrade because the JVM will trigger full garbage collection (GC) events in a struggle to free memory. + These full GC events are also called stop-the-world events as they completely halt the execution of the Java application. + Stop-the-world-events may take any where from a couple of milliseconds up to several minutes. + Should the heap memory demands rise even further the JVM will eventually throw an OutOfMemoryError which will cause the broker to shut down. + </p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="Java-Broker-Runtime-Memory-Low-Memory-Direct"></a>9.10.4.2. Low on Direct Memory</h4></div></div></div><p> + When the broker detects that it uses 40% of available direct memory it will start flowing incoming transient messages to disk and reading them back before delivery. + This will prevent the broker from running out of direct memory but may degrade performance by requiring disk I/O. + </p></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="Java-Broker-Runtime-Memory-Defaults"></a>9.10.5. Defaults</h3></div></div></div><p> + By default Qpid uses these settiongs: + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> + 0.5 GB heap memory + </li><li class="listitem"> + 1.5 GB direct memory + </li><li class="listitem"> + 5% of heap reserved for the JE cache. + </li><li class="listitem"> + Start flow-to-disk at 40% direct memory utilisation. + </li></ul></div><p> + As an example, this would accomodate a broker with 50 connections, each serving 5 sessions, and each session having 1000 messages of 1 kB on queues in the broker. + This means a total of 250 concurrent sessions and a total of 250000 messages without flowing messages to disk. + </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="Java-Broker-Runtime-Memory-Tuning"></a>9.10.6. Memory Tuning the Broker</h3></div></div></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="d0e5919"></a>9.10.6.1. Java Tuning</h4></div></div></div><p> + Most of these options are implementation specific. It is assumed you are using Oracle Java 1.7 and Qpid v6. + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> + Heap and direct memory can be configured through the <a class="link" href="Java-Broker-Appendix-Environment-Variables.html#Java-Broker-Appendix-Environment-Variables-Qpid-Java-Mem"><code class="literal">QPID_JAVA_MEM</code> environment variable</a>. + </li></ul></div><p> + </p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="d0e5933"></a>9.10.6.2. Qpid Tuning</h4></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> + The system property <code class="literal">qpid.broker.bdbTotalCacheSize</code> sets the total amount of heap memory (in bytes) allocated to BDB caches. + </li><li class="listitem"> + The system property <code class="literal">broker.flowToDiskThreshold</code> sets the threshold (in bytes) for flowing transient messages to disk. + Should the broker use more than direct memory it will flow incoming messages to disk. + Should utilisation fall beneath the threshold it will stop flowing messages to disk. + </li></ul></div></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="d0e5947"></a>9.10.6.3. Formulas</h4></div></div></div><p> + We developed a simple formula which estimates the <span class="emphasis"><em>minimum</em></span> memory usage of the broker under certain usage. + These are rough estimate so we strongly recommend testing your configuration extensively. + Also, if your machine has more memory available by all means use more memory as it can only improve the performance and stability of your broker. + However, remember that both heap and direct memory are served from your computer's physical memory so their sum should never exceed the physically available RAM (minus what other processes use). + </p><p> + <span class="mathphrase"> + memory<sub>heap</sub> = 15 MB + 15 kB * N<sub>sessions</sub> + 1 kB * N<sub>messages</sub> + 17 kB * N<sub>connections</sub> + </span> + <span class="mathphrase"> + memory<sub>direct</sub> = 2 MB + (200 B + averageSize<sub>msg</sub> *2)* N<sub>messages</sub> + 512 kB * N<sub>connections</sub> + </span> + Where <span class="mathphrase">N</span> denotes the total number of connections/sessions/messages on the broker. Furthermore, for direct memory only the messages that have not been flown to disk are relevant. + </p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="d0e5990"></a>9.10.6.4. Things to Consider</h4></div></div></div><div class="section"><div class="titlepage"><div><div><h5 class="title"><a id="d0e5993"></a>Performance</h5></div></div></div><p> + Choosing a smaller direct memory size will lower the threshold for flowing transient messages to disk when messages accumulate on a queue. + This can have impact on performance in the transient case where otherwise no disk I/O would be involved. + </p><p> + Having to little heap memory will result in poor performance due to frequent garbage collection events. See <a class="xref" href="Java-Broker-Runtime-Memory.html#Java-Broker-Runtime-Memory-Low-Memory" title="9.10.4. Low Memory Conditions">Section 9.10.4, “Low Memory Conditions”</a> for more details. + </p></div><div class="section"><div class="titlepage"><div><div><h5 class="title"><a id="d0e6002"></a>OutOfMemoryError</h5></div></div></div><p> + Choosing too low heap memory can cause an OutOfMemoryError which will force the broker to shut down. + In this sense the available heap memory puts a hard limit on the number of messages you can have in the broker at the same time. + </p><p> + If the Java runs out of direct memory it also throws a OutOfMemoryError resulting the a broker shutdown. + Under normal circumstances this should not happen but needs to be considered when deviating from the default configuration, especially when changing the flowToDiskThreshold. + </p><p> + If you are sending very large messages you should accommodate for this by making sure you have enough direct memory. + </p></div></div></div></div><div class="navfooter"><hr /><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="Java-Broker-Runtime-Connection-Limit.html">Prev</a> </td><td align="center" width="20%"><a accesskey="u" href="Java-Broker-Runtime.html">Up</a></td><td align="right" width="40%"> <a accesskey="n" href="Java-Broker-High-Availability.html">Next</a></td></tr><tr><td align="left" valign="top" width="40%">9.9. Connection Limits </td><td align="center" width="20%"><a accesskey="h" href="AMQP-Messaging-Broker-Java-Book.html">Home</a></td><td align="right" valign="top" width="40%"> Chapter 10. High Availability</td></tr></table></div></div> + + <hr/> + + <ul id="-apache-navigation"> + <li><a href="http://www.apache.org/";>Apache</a></li> + <li><a href="http://www.apache.org/licenses/";>License</a></li> + <li><a href="http://www.apache.org/foundation/sponsorship.html";>Sponsorship</a></li> + <li><a href="http://www.apache.org/foundation/thanks.html";>Thanks!</a></li> + <li><a href="http://www.apache.org/security/";>Security</a></li> + <li><a href="http://www.apache.org/";><img id="-apache-feather" width="48" height="14" src="" alt="Apache"/></a></li> + </ul> + + <p id="-legal"> + Apache Qpid, Messaging built on AMQP; Copyright © 2015 + The Apache Software Foundation; Licensed under + the <a href="http://www.apache.org/licenses/LICENSE-2.0";>Apache + License, Version 2.0</a>; Apache Qpid, Qpid, Qpid Proton, + Proton, Apache, the Apache feather logo, and the Apache Qpid + project logo are trademarks of The Apache Software + Foundation; All other marks mentioned may be trademarks or + registered trademarks of their respective owners + </p> + </div> + </div> + </div> + </body> +</html> http://git-wip-us.apache.org/repos/asf/qpid-site/blob/2069e43d/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Message-Compression.html ---------------------------------------------------------------------- diff --git a/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Message-Compression.html b/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Message-Compression.html new file mode 100644 index 0000000..b5a5ebc --- /dev/null +++ b/content/releases/qpid-java-6.0.3/java-broker/book/Java-Broker-Runtime-Message-Compression.html @@ -0,0 +1,158 @@ +<!DOCTYPE html> +<!-- + - + - Licensed to the Apache Software Foundation (ASF) under one + - or more contributor license agreements. 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This feature works in co-operation with Qpid + Clients implementing the same feature.</p><p>Once the feature is enabled (using Broker context variable + <span class="emphasis"><em>broker.messageCompressionEnabled</em></span>), the Broker will advertise support for the + message compression feature to the client at connection time. This allows clients to opt to turn + on message compression, allowing message payload sizes to be reduced.</p><p>If the Broker has connections from clients who have message compression enabled and others who + do not, it will internally, on-the-fly, decompress compressed messages when sending to clients + without support and conversely, compress uncomressed messages when sending to clients who do.</p><p>The Broker has a threshold below which it will not consider compressing a message, this is + controlled by Broker content variable + (<code class="literal">connection.messageCompressionThresholdSize</code>) and expresses a size in bytes.</p><p>This feature <span class="emphasis"><em>may</em></span> have a beneficial effect on performance by:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>Reducing the number of bytes transmitted over the wire, both between Client and Broker, and + in the HA case, Broker to Broker, for replication purposes.</p></li><li class="listitem"><p>Reducing storage space when data is at rest within the Broker, both on disk and in + memory.</p></li></ul></div><p>Of course, compression and decompression is computationally expensive. Turning on the feature + may have a negative impact on CPU utilization on Broker and/or Client. Also for small messages + payloads, message compression may increase the message size. It is recommended to test the feature + with representative data.</p><div class="footnotes"><br /><hr style="width:100; text-align:left;margin-left: 0" /><div class="footnote" id="ftn.d0e5714"><p><a class="para" href="#d0e5714"><sup class="para">[13] </sup></a>Message compression is not yet supported for the 1.0 + protocol.</p></div></div></div><div class="navfooter"><hr /><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="Java-Broker-Runtime-Background-Recovery.html">Prev</a> </td><td align="center" width="20%"><a accesskey="u" href="Java-Broker-Runtime.html">Up</a></td><td align="right" width="40%"> <a accesskey="n" href="Java-Broker-Runtime-Connection-Limit.html">Next</a></td></tr><tr><td align="left" valign="top" width="40%">9.7. Background Recovery </td><td align="center" width="20%"><a accesskey="h" href="AMQP-Messaging-Broker-Java-Book.html">Home</a></td><td align="right" valign="top" width="40%"> 9.9. Connection Limits</td></tr></table></div></div> + + <hr/> + + <ul id="-apache-navigation"> + <li><a href="http://www.apache.org/";>Apache</a></li> + <li><a href="http://www.apache.org/licenses/";>License</a></li> + <li><a href="http://www.apache.org/foundation/sponsorship.html";>Sponsorship</a></li> + <li><a href="http://www.apache.org/foundation/thanks.html";>Thanks!</a></li> + <li><a href="http://www.apache.org/security/";>Security</a></li> + <li><a href="http://www.apache.org/";><img id="-apache-feather" width="48" height="14" src="" alt="Apache"/></a></li> + </ul> + + <p id="-legal"> + Apache Qpid, Messaging built on AMQP; Copyright © 2015 + The Apache Software Foundation; Licensed under + the <a href="http://www.apache.org/licenses/LICENSE-2.0";>Apache + License, Version 2.0</a>; Apache Qpid, Qpid, Qpid Proton, + Proton, Apache, the Apache feather logo, and the Apache Qpid + project logo are trademarks of The Apache Software + Foundation; All other marks mentioned may be trademarks or + registered trademarks of their respective owners + </p> + </div> + </div> + </div> + </body> +</html> --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
