Corosync Cluster Engine

<h2 id="features">Features</h2>
<p>The Corosync Cluster Engine is a <a href="/facts/Group_communication_system/SFzUwufj">group communication system</a> with additional features for implementing <a href="/facts/High_availability/y3J8GnEo">high availability</a> within applications.
</p><p>The project provides four <a href="/facts/C_(programming_language)/Ky2No763">C</a> <a href="/facts/Application_programming_interface/GMlN4vUr">API</a> features:
</p>
<ul><li>A closed process group communication model with <a href="/facts/Virtual_synchrony/URHHI2Hw">virtual synchrony</a> guarantees for creating replicated <a href="/facts/State_machine/GMusWd0a">state machines</a>.</li>
<li>A simple availability manager that restarts the application process when it has failed.</li>
<li>A configuration and statistics <a href="/facts/In-memory_database/Am2VvJs4">in-memory database</a> that provides the ability to set, retrieve, and receive change notifications of information.</li>
<li>A <a href="/facts/Quorum_(Distributed_Systems)/gS6d6aPN">quorum</a> system that notifies applications when quorum is achieved or lost.</li></ul>
<p>The software is designed to operate on <a href="/facts/UDP/IP/dxLU0D6q">UDP/IP</a> and <a href="/facts/InfiniBand/6CUz47wQ">InfiniBand</a> networks.
</p>
<h2 id="architecture">Architecture</h2>
<p>The software is composed of an executive binary which uses a <a href="/facts/Client-server/FSnf27C5">client-server</a> communication model between libraries and service engines.  Loadable modules, called service engines, are loaded into the Corosync Cluster Engine and use the services provided by the Corosync Service Engine internal API.
</p><p>The services provided by the Corosync Service Engine internal API are:
</p>
<ul><li>An implementation of the Totem Single Ring Ordering and Membership<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> protocol providing the Extended Virtual Synchrony model<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> for messaging and membership.</li>
<li>The coroipc high performance <a href="/facts/Shared_memory_(interprocess_communication)/zmpH7WuV">shared memory</a> IPC system.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a></li>
<li>An object database that implements the <a href="/facts/In_memory_database/Am2VvJs4">in memory database</a> model.</li>
<li>Systems to route IPC and Totem messages to the correct service engines.</li></ul>
<p>Additionally Corosync provides several default service engines that are used via C <a href="/facts/Application_programming_interface/GMlN4vUr">APIs</a>:
</p>
<ul><li>cpg - Closed Process Group</li>
<li>sam - Simple Availability Manager</li>
<li>confdb - Configuration and Statistics database</li>
<li>quorum - Provides notifications of gain or loss of quorum</li></ul>
<h2 id="history">History</h2>
<p>The project was formally announced in July 2008 via a conference paper at the <a href="/facts/Ottawa_Linux_Symposium/NmtVfDd2">Ottawa Linux Symposium</a>.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> The source code of OpenAIS was <a href="/facts/Refactored/gkw9oVTE">refactored</a> such that the core infrastructure components were placed into Corosync and the <a href="/facts/SA_Forum/kgPXlLTM">SA Forum</a> APIs were kept in OpenAIS.
</p><p>In the second version of corosync, published in 2012, quorum subsystem was changed and integrated into the daemon.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> This version is available since Fedora 17 and RHEL7.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a>
</p><p>Flatiron branch (1.4.x) development ended with 1.4.10 release.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> Needle branch was announced stable with 2.0.0 release on 10 April 2012.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a><a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> Development of this branch stopped with 2.4.6 release on 9 November 2022, because 3.x branch (Camelback) was considered to be stable after almost 4 years of work.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a>
</p>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Linux-HA/Gk2o3WgD">Linux-HA</a></li>
<li><a href="/facts/Pacemaker_(software)/l7CS7uxI">Pacemaker (software)</a></li></ul>

<h2 id="external-links">External links</h2>
<ul><li><a href="http://corosync.github.io/corosync/">Official website</a></li>
<li>"The Totem Single-Ring Ordering and Membership Protocol". <a href="/facts/CiteSeerX_(identifier)/SceDmd3c">CiteSeerX</a> <a href="https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.37.767">10.1.1.37.767</a>. {{cite journal}}: Cite journal requires |journal= (help)</li>
<li>"Totem: A Reliable Ordered Delivery Protocol for Interconnected Local-Area Networks". <a href="/facts/CiteSeerX_(identifier)/SceDmd3c">CiteSeerX</a> <a href="https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.52.4028">10.1.1.52.4028</a>. {{cite journal}}: Cite journal requires |journal= (help)</li>
<li>"Extended Virtual Synchrony model". <a href="/facts/CiteSeerX_(identifier)/SceDmd3c">CiteSeerX</a> <a href="https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.55.8677">10.1.1.55.8677</a>. {{cite journal}}: Cite journal requires |journal= (help)</li>
<li><a href="https://www.kernel.org/doc/ols/2009/ols2009-pages-61-68.pdf">Corosync High Performance Shared Memory IPC Reusable C Library</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Amir, Y.; Moser, L.E.; Melliar-Smith, P.M.; Agarwal, D.A.; Ciarfella, P. (November 1995). "The Totem Single Ring Ordering and Membership Protocol". ACM Transactions on Computer Systems. 13 (4): 311–342. doi:10.1145/210223.210224. S2CID 15165593. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Moser, L.E.; Amir, Y.; Melliar-Smith, P.M.; Agarwal, D.A. (November 1995). "Extended Virtual Synchrony". ACM Transactions on Computer Systems. 13 (4): 311–342. doi:10.1145/210223.210224. S2CID 15165593. Also in Proceedings of DCS, pp. 56-65, 1994. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Dake, S. (July 2009). "The Corosync High Performance Shared Memory IPC Reusable C Library" (PDF). Proceedings of the Linux Symposium: 61–68. <a href="https://www.kernel.org/doc/ols/2009/ols2009-pages-61-68.pdf" target="_blank">https://www.kernel.org/doc/ols/2009/ols2009-pages-61-68.pdf</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Dake, S.; Caulfield, C.; Beekhof, A. (July 2008). "The Corosync Cluster Engine" (PDF). Proceedings of the Linux Symposium: 85–99. <a href="https://www.kernel.org/doc/ols/2008/ols2008v1-pages-85-100.pdf" target="_blank">https://www.kernel.org/doc/ols/2008/ols2008v1-pages-85-100.pdf</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>Christine Caulfield,New quorum features in Corosync 2 - 2012-2016 (in English) <a href="http://people.redhat.com/ccaulfie/docs/Votequorum_Intro.pdf" target="_blank">http://people.redhat.com/ccaulfie/docs/Votequorum_Intro.pdf</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>Linux Cluster next generation, LVEE, 2013 <a href="https://lvee.org/uploads/image_upload/file/267/Linux_Clusters_at_LVEE_2013.pdf" target="_blank">https://lvee.org/uploads/image_upload/file/267/Linux_Clusters_at_LVEE_2013.pdf</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>"Releases v1.4.10". GitHub. Retrieved 23 November 2022. <a href="https://github.com/corosync/corosync/releases/tag/v1.4.10" target="_blank">https://github.com/corosync/corosync/releases/tag/v1.4.10</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
<li id="fn:8"><p>"Releases v2.4.6". GitHub. Retrieved 23 November 2022. <a href="https://github.com/corosync/corosync/releases/tag/v2.4.6" target="_blank">https://github.com/corosync/corosync/releases/tag/v2.4.6</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li>
<li id="fn:9"><p>"Releases v2.0.0". GitHub. Retrieved 23 November 2022. <a href="https://github.com/corosync/corosync/releases/tag/v2.0.0" target="_blank">https://github.com/corosync/corosync/releases/tag/v2.0.0</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li>
<li id="fn:10"><p>"Releases v2.4.6". GitHub. Retrieved 23 November 2022. <a href="https://github.com/corosync/corosync/releases/tag/v2.4.6" target="_blank">https://github.com/corosync/corosync/releases/tag/v2.4.6</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li>
</ol>

Corosync Cluster Engine open-in-new

Corosync Cluster Engine