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diff --git a/documentation/content/xdocs/Reliability Requirements.html b/documentation/content/xdocs/Reliability Requirements.html new file mode 100755 index 0000000000..9cdf026009 --- /dev/null +++ b/documentation/content/xdocs/Reliability Requirements.html @@ -0,0 +1,96 @@ +<html> + <head> + <title>Apache Qpid : Reliability Requirements</title> + <link rel="stylesheet" href="styles/site.css" type="text/css" /> + <META http-equiv="Content-Type" content="text/html; charset=UTF-8"> + </head> + + <body> + <table class="pagecontent" border="0" cellpadding="0" cellspacing="0" width="100%" bgcolor="#ffffff"> + <tr> + <td valign="top" class="pagebody"> + <div class="pageheader"> + <span class="pagetitle"> + Apache Qpid : Reliability Requirements + </span> + </div> + <div class="pagesubheading"> + This page last changed on Jun 11, 2007 by <font color="#0050B2">aconway</font>. + </div> + + <h1><a name="ReliabilityRequirements-ReliabilityRequirements"></a>Reliability Requirements</h1> + + +<h2><a name="ReliabilityRequirements-Failover%28sessionstate%29"></a>Fail-over (session state)</h2> + +<p>A cluster member informs its clients of backup candidates for each session. It can update the list periodically.</p> + +<p>After an unexpected disconnect the client can connect to one of the candidates and resume its session transparently. All session state is preserved including:</p> +<ul> + <li>Open references</li> + <li>Active consumers</li> + <li>Commands-in-flight</li> + <li>Open transactions (question: Is there any value in fail-over that aborts TX and/or DTX transactions?)</li> +</ul> + + +<p>Sessions <em>do not</em> survive</p> +<ul> + <li>multiple failures that include the current node and all back-up nodes for that session.</li> + <li>shutdown/restart of the cluster.</li> +</ul> + + +<h2><a name="ReliabilityRequirements-ClusterRestart%28durableresources%29"></a>Cluster Restart (durable resources)</h2> + +<p>The AMQP entities that survive a restart are those defined by AMQP to survive broker restart. AMQP defines <em>durable</em> exchanges and queues and <em>persistent</em> messages. Some further definitions:</p> +<ul> + <li><em>durable</em> message: persistent messages on a durable queues.</li> + <li><em>durable</em> enque: act of enqueuing a persistent message on a durable queue.</li> + <li><em>durable</em> binding: binding between durable exchange and durable queue.</li> +</ul> + + +<p>The following are preserved if the entire cluster shuts down/crashes and is re-started:</p> +<ul> + <li><em>Durable</em> wiring: durable exchanges, queues and bindings.</li> + <li><em>Durable</em> messages</li> + <li><em>Prepared</em> DTX transactions</li> +</ul> + + +<p>The following do not survive a restart:</p> +<ul> + <li>Session state</li> + <li>Non-durable wiring</li> + <li>TX transactions are aborted.</li> + <li>Unprepared DTX transactions are aborted.</li> + <li>Non-durable effects of prepared DTX transactions are lost.</li> +</ul> + + +<h3><a name="ReliabilityRequirements-RestartingDTXTransactions"></a>Restarting DTX Transactions</h3> + +<p>On restart, prepared DTX transactions may commit or rollback. In either case the outcome is <em>as if</em> the transaction had comitted or rolled back just <em>before</em> the restart: All durable transaction effects survive the restart, all non-durable effects are lost.</p> + +<p>In particular</p> +<ul> + <li>On <b><em>commit</em></b><b>:</b> <em>non durable</em> messages enqueued in the transaction are <em>lost</em>, as if they had been enqueued before the restart and were lost in the restart.</li> + <li>On <b><em>rollback:</em></b> <em>non durable</em> messages dequeued in the transaction are <em>lost</em>, as if they had been put back on the queue before restart and then lost in the restart.</li> +</ul> + + + + </td> + </tr> + </table> + <table border="0" cellpadding="0" cellspacing="0" width="100%"> + <tr> + <td height="12" background="border/border_bottom.gif"><img src="border/spacer.gif" width="1" height="1" border="0"/></td> + </tr> + <tr> + <td align="center"><font color="grey">Document generated by Confluence on Apr 22, 2008 02:47</font></td> + </tr> + </table> + </body> +</html>
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