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| <section xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="Java-Broker-Runtime-Background-Recovery"> |
| <title>Background Recovery</title> |
| <para>On startup of the Broker, or restart of a Virtualhost, the Broker restores all durable |
| queues and their messages from disk. In the Broker's default mode the Virtualhosts do not become |
| active until this recovery process completes. If queues have a large number of entries, this may |
| take considerable time. During this time no messaging can be performed.</para> |
| <para>The Broker has a background recovery feature allows the system to return to operation |
| sooner. If enabled the recovery process takes place in the background allow producers and |
| consumers to begin work earlier.</para> |
| <para>The feature respects the message delivery order requirements of standard queues, that is any |
| messages arriving whilst the background recovery is in flight won't overtake older messages |
| still to be recovered from disk. There is an exception for the out of order queue types whilst |
| background recovery is in flight. For instance, with priority queues older lower priority |
| messages may be delivered before newer, higher priority.</para> |
| <para>To activate the feature, set a <link linkend="Java-Broker-Management-Managing-Entities-General">context variable</link> |
| <literal>use_async_message_store_recovery</literal> at the desired Virtualhost, or at Broker or |
| higher to enable the feature broker-wide.</para> |
| <note> |
| <para>The background recovery feature does not write operational log messages to indicate its |
| progress. This means messages <link linkend="Java-Broker-Appendix-Operation-Logging-Message-MST-1004">MST-1004</link> and <link linkend="Java-Broker-Appendix-Operation-Logging-Message-MST-1005">MST-1005</link> will not |
| be seen.</para> |
| </note> |
| </section> |
