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<span>Architecture</span> </div> </a> <ul id="toc-Architecture-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Use_cases" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Use_cases"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Use cases</span> </div> </a> <ul id="toc-Use_cases-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Client_libraries" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Client_libraries"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Client libraries</span> </div> </a> <ul id="toc-Client_libraries-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Apache_projects_using_ZooKeeper" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Apache_projects_using_ZooKeeper"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Apache projects using ZooKeeper</span> </div> </a> <ul id="toc-Apache_projects_using_ZooKeeper-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div 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searchaux" style="display:none">System for distributed coordination</div> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox vevent"><caption class="infobox-title summary">Apache ZooKeeper</caption><tbody><tr><td colspan="2" class="infobox-image logo"><span class="mw-default-size" typeof="mw:File/Frameless"><a href="/wiki/File:Apache_ZooKeeper_logo.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/77/Apache_ZooKeeper_logo.svg/220px-Apache_ZooKeeper_logo.svg.png" decoding="async" width="220" height="119" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/77/Apache_ZooKeeper_logo.svg/330px-Apache_ZooKeeper_logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/77/Apache_ZooKeeper_logo.svg/440px-Apache_ZooKeeper_logo.svg.png 2x" data-file-width="864" data-file-height="467" /></a></span></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Programmer" title="Programmer">Developer(s)</a></th><td class="infobox-data"><a href="/wiki/Apache_Software_Foundation" class="mw-redirect" title="Apache Software Foundation">Apache Software Foundation</a></td></tr><tr style="display: none;"><td colspan="2" class="infobox-full-data"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1257001546"></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Software_release_life_cycle" title="Software release life cycle">Stable release</a></th><td class="infobox-data"><div style="margin:0px;">3.8.1 / January 30, 2023<span class="noprint">; 2 years ago</span><span style="display:none"> (<span class="bday dtstart published updated">2023-01-30</span>)</span><sup id="cite_ref-releases_1-0" class="reference"><a href="#cite_note-releases-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></div></td></tr><tr style="display:none"><td colspan="2"> </td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Repository_(version_control)" title="Repository (version control)">Repository</a></th><td class="infobox-data"><span class="url"><a rel="nofollow" class="external text" href="https://gitbox.apache.org/repos/asf?p=zookeeper.git">ZooKeeper Repository</a></span></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Written in</th><td class="infobox-data"><a href="/wiki/Java_(programming_language)" title="Java (programming language)">Java</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Operating_system" title="Operating system">Operating system</a></th><td class="infobox-data"><a href="/wiki/Cross-platform" class="mw-redirect" title="Cross-platform">Cross-platform</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Software_categories#Categorization_approaches" title="Software categories">Type</a></th><td class="infobox-data"><a href="/wiki/Distributed_computing" title="Distributed computing">Distributed computing</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;"><a href="/wiki/Software_license" title="Software license">License</a></th><td class="infobox-data"><a href="/wiki/Apache_License_2.0" class="mw-redirect" title="Apache License 2.0">Apache License 2.0</a></td></tr><tr><th scope="row" class="infobox-label" style="white-space: nowrap;">Website</th><td class="infobox-data"><span class="url"><a rel="nofollow" class="external text" href="https://zookeeper.apache.org">zookeeper<wbr />.apache<wbr />.org</a></span></td></tr></tbody></table> <p><b>Apache ZooKeeper</b> is an open-source server for highly reliable distributed coordination of cloud applications.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> It is a project of the <a href="/wiki/Apache_Software_Foundation" class="mw-redirect" title="Apache Software Foundation">Apache Software Foundation</a>. </p><p>ZooKeeper is essentially a <a href="/wiki/Service_(systems_architecture)" title="Service (systems architecture)">service</a> for <a href="/wiki/Distributed_computing" title="Distributed computing">distributed systems</a> offering a <a href="/wiki/Hierarchical_database_model" title="Hierarchical database model">hierarchical</a> <a href="/wiki/Key-value_database" class="mw-redirect" title="Key-value database">key-value store</a>, which is used to provide a distributed <a href="/wiki/Configuration_management" title="Configuration management">configuration service</a>, <a href="/wiki/Synchronization_(computer_science)" title="Synchronization (computer science)">synchronization service</a>, and <a href="/wiki/Directory_service" title="Directory service">naming registry</a> for large distributed systems (see <i><a href="#Use_cases">Use cases</a></i>).<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> ZooKeeper was a sub-project of <a href="/wiki/Hadoop" class="mw-redirect" title="Hadoop">Hadoop</a> but is now a <a href="/wiki/Apache_Software_Foundation#Projects" class="mw-redirect" title="Apache Software Foundation">top-level Apache project</a> in its own right. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Overview">Overview</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apache_ZooKeeper&action=edit&section=1" title="Edit section: Overview"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>ZooKeeper's <a href="/wiki/Software_architecture" title="Software architecture">architecture</a> supports <a href="/wiki/High-availability_cluster" title="High-availability cluster">high availability</a> through <a href="/wiki/Redundancy_(engineering)" title="Redundancy (engineering)">redundant services</a>. The clients can thus ask another ZooKeeper leader if the first fails to answer. ZooKeeper nodes store their data in a hierarchical name space, much like a file system or a <a href="/wiki/Tree_(data_structure)" class="mw-redirect" title="Tree (data structure)">tree</a> data structure. Clients can read from and write to the nodes and in this way have a shared configuration service. ZooKeeper can be viewed as an <a href="/wiki/Atomic_broadcast" title="Atomic broadcast">atomic broadcast</a> system, through which updates are <a href="/wiki/Total_order" title="Total order">totally ordered</a>. The ZooKeeper Atomic Broadcast (ZAB) protocol is the core of the system.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>ZooKeeper is used by companies including <a href="/wiki/Yelp" title="Yelp">Yelp</a>, <a href="/wiki/Rackspace" class="mw-redirect" title="Rackspace">Rackspace</a>, <a href="/wiki/Yahoo!" class="mw-redirect" title="Yahoo!">Yahoo!</a>,<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Odnoklassniki" title="Odnoklassniki">Odnoklassniki</a>, <a href="/wiki/Reddit" title="Reddit">Reddit</a>,<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> <a href="/wiki/NetApp" title="NetApp">NetApp</a> <a href="/wiki/SolidFire" class="mw-redirect" title="SolidFire">SolidFire</a>,<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Meta_Platforms" title="Meta Platforms">Meta</a>,<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Twitter" title="Twitter">Twitter</a><sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> and <a href="/wiki/EBay" title="EBay">eBay</a> as well as <a href="/wiki/Open-source_software" title="Open-source software">open source</a> <a href="/wiki/Enterprise_search" title="Enterprise search">enterprise search</a> systems like <a href="/wiki/Solr" class="mw-redirect" title="Solr">Solr</a> and distributed database systems like <a href="/wiki/Apache_Pinot" title="Apache Pinot">Apache Pinot</a>.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p><p>ZooKeeper is modeled after Google's Chubby lock service<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> and was originally developed at Yahoo! for streamlining the processes running on big-data clusters by storing the status in local log files on the ZooKeeper servers. These servers communicate with the client machines to provide them the information. ZooKeeper was developed in order to fix the bugs that occurred while deploying distributed big-data applications. </p><p>Some of the prime features of Apache ZooKeeper are: </p> <ul><li>Reliable System: This system is fairly reliable as it keeps working even if some nodes stop working.</li> <li>Simple Architecture: The architecture of ZooKeeper is quite simple as there is a shared hierarchical namespace which helps coordinating the processes.</li> <li>Fast Processing: ZooKeeper is especially fast in "read-dominant" workloads (i.e. workloads in which reads are much more common than writes).</li> <li>Scalable: The performance of ZooKeeper can be improved by adding nodes.</li></ul> <div class="mw-heading mw-heading2"><h2 id="Architecture">Architecture</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apache_ZooKeeper&action=edit&section=2" title="Edit section: Architecture"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Some common terminologies regarding the ZooKeeper architecture: </p> <ul><li>Node: The systems installed on the cluster</li> <li>ZNode: The nodes where the status is updated by other nodes in cluster</li> <li>Client applications: The tools that interact with the distributed applications</li> <li>Server applications: Allows the client applications to interact using a common interface</li></ul> <p>The services in the cluster are replicated and stored on a set of servers (called an "ensemble"), each of which maintains an in-memory database containing the entire data tree of state as well as a transaction log and snapshots stored persistently. Multiple client applications can connect to a server, and each client maintains a TCP connection through which it sends requests and heartbeats and receives responses and watch events for monitoring.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Use_cases">Use cases</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apache_ZooKeeper&action=edit&section=3" title="Edit section: Use cases"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Typical use cases for ZooKeeper are: </p> <ul><li><a href="/wiki/Name_service" class="mw-redirect" title="Name service">Naming service</a></li> <li><a href="/wiki/Configuration_management" title="Configuration management">Configuration management</a></li> <li><a href="/wiki/Synchronization_(computer_science)" title="Synchronization (computer science)">Data Synchronization</a></li> <li><a href="/wiki/Leader_election" title="Leader election">Leader election</a></li> <li><a href="/wiki/Message_queue" title="Message queue">Message queue</a></li> <li><a href="/wiki/Notification_system" title="Notification system">Notification system</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Client_libraries">Client libraries</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apache_ZooKeeper&action=edit&section=4" title="Edit section: Client libraries"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In addition to the client libraries included with the ZooKeeper distribution, a number of third-party libraries such as Apache Curator and Kazoo are available that make using ZooKeeper easier, add additional functionality, additional programming languages, etc. </p> <div class="mw-heading mw-heading2"><h2 id="Apache_projects_using_ZooKeeper">Apache projects using ZooKeeper</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apache_ZooKeeper&action=edit&section=5" title="Edit section: Apache projects using ZooKeeper"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Apache_Hadoop" title="Apache Hadoop">Apache Hadoop</a></li> <li><a href="/wiki/Apache_Accumulo" title="Apache Accumulo">Apache Accumulo</a></li> <li><a href="/wiki/Apache_HBase" title="Apache HBase">Apache HBase</a></li> <li><a href="/wiki/Apache_Hive" title="Apache Hive">Apache Hive</a></li> <li><a href="/wiki/Apache_Kafka" title="Apache Kafka">Apache Kafka</a></li> <li><a href="/wiki/Apache_Drill" title="Apache Drill">Apache Drill</a></li> <li><a href="/wiki/Apache_Solr" title="Apache Solr">Apache Solr</a></li> <li><a href="/wiki/Apache_Spark" title="Apache Spark">Apache Spark</a></li> <li><a href="/wiki/Apache_NiFi" title="Apache NiFi">Apache NiFi</a></li> <li><a href="/wiki/Apache_Druid" title="Apache Druid">Apache Druid</a></li> <li><a href="/wiki/Apache_Helix" title="Apache Helix">Apache Helix</a></li> <li><a href="/wiki/Apache_Pinot" title="Apache Pinot">Apache Pinot</a></li> <li><a href="/w/index.php?title=Apache_Bookkeeper&action=edit&redlink=1" class="new" title="Apache Bookkeeper (page does not exist)">Apache Bookkeeper</a></li> <li><a href="/w/index.php?title=Apache_Pulsar&action=edit&redlink=1" class="new" title="Apache Pulsar (page does not exist)">Apache Pulsar</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Apache_ZooKeeper&action=edit&section=6" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1266661725">.mw-parser-output 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Retrieved <span class="nowrap">12 February</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Apache+ZooKeeper+-+Releases&rft_id=https%3A%2F%2Fzookeeper.apache.org%2Freleases.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApache+ZooKeeper" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://zookeeper.apache.org/">"Apache Zookeeper4"</a><span class="reference-accessdate">. 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Retrieved <span class="nowrap">2017-05-24</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=NetApp+Newsroom&rft.atitle=5+Big+DaaS+Challenges+and+How+to+Overcome+Them+%7C+NetApp+Newsroom&rft.date=2016-06-20&rft_id=https%3A%2F%2Fnewsroom.netapp.com%2Fblogs%2F5-big-daas-challenges-and-how-to-overcome-them%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApache+ZooKeeper" class="Z3988"></span><sup class="noprint Inline-Template"><span style="white-space: nowrap;">[<i><a href="/wiki/Wikipedia:Link_rot" title="Wikipedia:Link rot"><span title=" Dead link tagged October 2019">permanent dead link</span></a></i><span style="visibility:hidden; color:transparent; padding-left:2px">‍</span>]</span></sup></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation news cs1"><a rel="nofollow" class="external text" href="https://code.fb.com/data-infrastructure/location-aware-distribution-configuring-servers-at-scale/">"Location-Aware Distribution: Configuring servers at scale"</a>. <i>Facebook Code</i>. 2018-07-19<span class="reference-accessdate">. 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Retrieved <span class="nowrap">2018-12-08</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Twitter+Engineering+Blog&rft.atitle=ZooKeeper+at+Twitter&rft.date=2018-10-11&rft_id=https%3A%2F%2Fblog.twitter.com%2Fengineering%2Fen_us%2Ftopics%2Finfrastructure%2F2018%2Fzookeeper-at-twitter.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApache+ZooKeeper" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://cwiki.apache.org/confluence/display/solr/SolrCloud">"SolrCloud"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=SolrCloud&rft_id=https%3A%2F%2Fcwiki.apache.org%2Fconfluence%2Fdisplay%2Fsolr%2FSolrCloud&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApache+ZooKeeper" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://docs.pinot.apache.org/basics/architecture">"Apache Pinot: Architecture"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Apache+Pinot%3A+Architecture&rft_id=https%3A%2F%2Fdocs.pinot.apache.org%2Fbasics%2Farchitecture&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApache+ZooKeeper" class="Z3988"></span></span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBurrows2006" class="citation journal cs1">Burrows, Mike (2006). <a rel="nofollow" class="external text" href="https://research.google/pubs/pub27897/">"The Chubby lock service for loosely-coupled distributed systems"</a>. <i>7th USENIX Symposium on Operating Systems Design and Implementation (OSDI)</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=7th+USENIX+Symposium+on+Operating+Systems+Design+and+Implementation+%28OSDI%29&rft.atitle=The+Chubby+lock+service+for+loosely-coupled+distributed+systems&rft.date=2006&rft.aulast=Burrows&rft.aufirst=Mike&rft_id=https%3A%2F%2Fresearch.google%2Fpubs%2Fpub27897%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AApache+ZooKeeper" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFChandraGriesemerRedstone2007" class="citation web cs1">Chandra, Tushar Deepak; Griesemer, Robert; Redstone, Joshua (2007). <a rel="nofollow" class="external text" href="https://research.google/pubs/pub33002/">"Paxos Made Live - An Engineering Perspective (2006 Invited Talk)"</a>. <i>Google Research</i><span class="reference-accessdate">. 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href="/wiki/Apache_OFBiz" title="Apache OFBiz">OFBiz</a></li> <li><a href="/wiki/Apache_Oozie" title="Apache Oozie">Oozie</a></li> <li><a href="/wiki/Apache_OpenEJB" title="Apache OpenEJB">OpenEJB</a></li> <li><a href="/wiki/Apache_OpenJPA" title="Apache OpenJPA">OpenJPA</a></li> <li><a href="/wiki/Apache_OpenNLP" title="Apache OpenNLP">OpenNLP</a></li> <li><a href="/wiki/Apache_OpenOffice" title="Apache OpenOffice">OрenOffice</a></li> <li><a href="/wiki/Apache_ORC" title="Apache ORC">ORC</a></li> <li><a href="/wiki/Apache_PDFBox" title="Apache PDFBox">PDFBox</a></li> <li><a href="/wiki/Apache_Parquet" title="Apache Parquet">Parquet</a></li> <li><a href="/wiki/Apache_Phoenix" title="Apache Phoenix">Phoenix</a></li> <li><a href="/wiki/Apache_POI" title="Apache POI">POI</a></li> <li><a href="/wiki/Apache_Pig" title="Apache Pig">Pig</a></li> <li><a href="/wiki/Apache_Pinot" title="Apache Pinot">Pinot</a></li> <li><a href="/wiki/Apache_Pivot" title="Apache Pivot">Pivot</a></li> <li><a href="/wiki/Apache_Qpid" title="Apache Qpid">Qpid</a></li> <li><a href="/wiki/Apache_Roller" title="Apache Roller">Roller</a></li> <li><a href="/wiki/Apache_RocketMQ" title="Apache RocketMQ">RocketMQ</a></li> <li><a href="/wiki/Apache_Samza" title="Apache Samza">Samza</a></li> <li><a href="/wiki/Apache_Shiro" title="Apache Shiro">Shiro</a></li> <li><a href="/wiki/Apache_SINGA" title="Apache SINGA">SINGA</a></li> <li><a href="/wiki/Apache_Sling" title="Apache Sling">Sling</a></li> <li><a href="/wiki/Apache_Solr" title="Apache Solr">Solr</a></li> <li><a href="/wiki/Apache_Spark" title="Apache Spark">Spark</a></li> <li><a href="/wiki/Apache_Storm" title="Apache Storm">Storm</a></li> <li><a href="/wiki/Apache_SpamAssassin" title="Apache SpamAssassin">SpamAssassin</a></li> <li><a href="/wiki/Apache_Struts" title="Apache Struts">Struts</a> <ul><li><a href="/wiki/Apache_Struts_1" title="Apache Struts 1">1</a></li></ul></li> <li><a href="/wiki/Apache_Subversion" title="Apache Subversion">Subversion</a></li> <li><a href="/wiki/Apache_Superset" title="Apache Superset">Superset</a></li> <li><a href="/wiki/Apache_SystemDS" title="Apache SystemDS">SystemDS</a></li> <li><a href="/wiki/Apache_Tapestry" title="Apache Tapestry">Tapestry</a></li> <li><a href="/wiki/Apache_Thrift" title="Apache Thrift">Thrift</a></li> <li><a href="/wiki/Apache_Tika" title="Apache Tika">Tika</a></li> <li><a href="/wiki/Apache_TinkerPop" class="mw-redirect" title="Apache TinkerPop">TinkerPop</a></li> <li><a href="/wiki/Apache_Tomcat" title="Apache Tomcat">Tomcat</a></li> <li><a href="/wiki/Apache_Trafodion" class="mw-redirect" title="Apache Trafodion">Trafodion</a></li> <li><a href="/wiki/Apache_Traffic_Server" title="Apache Traffic Server">Traffic Server</a></li> <li><a href="/wiki/UIMA" title="UIMA">UIMA</a></li> <li><a href="/wiki/Apache_Velocity" title="Apache Velocity">Velocity</a></li> <li><a href="/wiki/Apache_Wicket" title="Apache Wicket">Wicket</a></li> <li><a href="/wiki/Apache_Xalan" title="Apache Xalan">Xalan</a></li> <li><a href="/wiki/Apache_Xerces" title="Apache Xerces">Xerces</a></li> <li><a href="/wiki/Apache_XMLBeans" title="Apache XMLBeans">XMLBeans</a></li> <li>Yetus</li> <li><a class="mw-selflink selflink">ZooKeeper</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Apache_Commons" title="Apache Commons">Commons</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Byte_Code_Engineering_Library" title="Byte Code Engineering Library">BCEL</a></li> <li><a href="/wiki/Bean_Scripting_Framework" title="Bean Scripting Framework">BSF</a></li> <li><a href="/wiki/Commons_Daemon" title="Commons Daemon">Daemon</a></li> <li><a href="/wiki/Apache_Jelly" title="Apache Jelly">Jelly</a></li> <li><a href="/wiki/Apache_Commons_Logging" title="Apache Commons Logging">Logging</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Incubator</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Apache_Taverna" title="Apache Taverna">Taverna</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other projects</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Apache_Batik" title="Apache Batik">Batik</a></li> <li><a href="/wiki/Apache_FOP_(Formatting_Objects_Processor)" class="mw-redirect" title="Apache FOP (Formatting Objects Processor)">FOP</a></li> <li><a href="/wiki/Apache_Ivy" title="Apache Ivy">Ivy</a></li> <li><a href="/wiki/Log4j" title="Log4j">Log4j</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Attic</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Apache_Apex" title="Apache Apex">Apex</a></li> <li><a href="/wiki/AxKit" title="AxKit">AxKit</a></li> <li><a href="/wiki/Apache_Beehive" title="Apache Beehive">Beehive</a></li> <li><a href="/wiki/Apache_iBATIS" title="Apache iBATIS">iBATIS</a></li> <li><a href="/wiki/Apache_Click" title="Apache Click">Click</a></li> <li><a href="/wiki/Apache_Continuum" title="Apache Continuum">Continuum</a></li> <li><a href="/wiki/Deltacloud" title="Deltacloud">Deltacloud</a></li> <li><a href="/wiki/Etch_(protocol)" title="Etch (protocol)">Etch</a></li> <li><a href="/wiki/Apache_Giraph" title="Apache Giraph">Giraph</a></li> <li><a href="/wiki/Apache_Hama" title="Apache Hama">Hama</a></li> <li><a href="/wiki/Apache_Harmony" title="Apache Harmony">Harmony</a></li> <li><a href="/wiki/Jakarta_Project" title="Jakarta Project">Jakarta</a></li> <li><a href="/wiki/Apache_Marmotta" title="Apache Marmotta">Marmotta</a></li> <li><a href="/wiki/Apache_MXNet" title="Apache MXNet">MXNet</a></li> <li><a href="/wiki/Apache_ODE" title="Apache ODE">ODE</a></li> <li><a href="/wiki/Jini" title="Jini">River</a></li> <li><a href="/wiki/Apache_Shale" title="Apache Shale">Shale</a></li> <li><a href="/wiki/Jakarta_Slide" class="mw-redirect" title="Jakarta Slide">Slide</a></li> <li><a href="/wiki/Sqoop" title="Sqoop">Sqoop</a></li> <li><a href="/wiki/Apache_Stanbol" title="Apache Stanbol">Stanbol</a></li> <li><a href="/wiki/Apache_Tuscany" class="mw-redirect" title="Apache Tuscany">Tuscany</a></li> <li><a href="/wiki/Apache_Wave" class="mw-redirect" title="Apache Wave">Wave</a></li> <li><a href="/wiki/Apache_XML" title="Apache XML">XML</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Licenses</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Apache_License" title="Apache License">Apache 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href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Java_(software_platform)462" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="3"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Java_(software_platform)" title="Template:Java (software platform)"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Java_(software_platform)" title="Template talk:Java (software platform)"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Java_(software_platform)" title="Special:EditPage/Template:Java (software platform)"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Java_(software_platform)462" style="font-size:114%;margin:0 4em"><a href="/wiki/Java_(software_platform)" title="Java (software platform)">Java (software platform)</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Platforms</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Java_virtual_machine" title="Java virtual machine">JVM</a></li> <li><a href="/wiki/Java_Platform,_Micro_Edition" title="Java Platform, Micro Edition">Java ME</a> (Micro)</li> <li><a href="/wiki/Java_Platform,_Standard_Edition" title="Java Platform, Standard Edition">Java SE</a> (Standard)</li> <li><a href="/wiki/Jakarta_EE" title="Jakarta EE">Jakarta EE</a> (Enterprise)</li> <li><a href="/wiki/Java_Card" title="Java Card">Java Card</a></li> <li><a href="/wiki/Android_software_development#SDK" title="Android software development">Android SDK</a></li> <li><a href="/wiki/GraalVM" title="GraalVM">GraalVM</a></li></ul> </div></td><td class="noviewer navbox-image" rowspan="7" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"><a href="/wiki/File:Duke_(Java_mascot)_waving.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/5d/Duke_%28Java_mascot%29_waving.svg/75px-Duke_%28Java_mascot%29_waving.svg.png" decoding="async" width="75" height="135" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/5d/Duke_%28Java_mascot%29_waving.svg/113px-Duke_%28Java_mascot%29_waving.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/5d/Duke_%28Java_mascot%29_waving.svg/150px-Duke_%28Java_mascot%29_waving.svg.png 2x" data-file-width="226" data-file-height="407" /></a></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Oracle technologies</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Squawk_virtual_machine" title="Squawk virtual machine">Squawk</a></li> <li><a href="/wiki/Java_Development_Kit" title="Java Development Kit">Java Development Kit</a></li> <li><a href="/wiki/OpenJDK" title="OpenJDK">OpenJDK</a></li> <li><a href="/wiki/Java_virtual_machine" title="Java virtual machine">Java virtual machine</a></li> <li><a href="/wiki/JavaFX" title="JavaFX">JavaFX</a></li> <li><a href="/wiki/Maxine_Virtual_Machine" title="Maxine Virtual Machine">Maxine VM</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Platform technologies</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Jakarta_Servlet" title="Jakarta Servlet">Servlets</a></li> <li><a href="/wiki/MIDlet" title="MIDlet">MIDlets</a></li> <li><a href="/wiki/Jakarta_Server_Pages" title="Jakarta Server Pages">JSP</a></li> <li><a href="/wiki/Jakarta_Faces" title="Jakarta Faces">JSF</a></li> <li><a href="/wiki/Java_Web_Start" title="Java Web Start">Web Start</a> (JNLP)</li> <li><a href="/wiki/Pack200" title="Pack200">Pack200</a></li> <li><a href="/wiki/Java_Platform_Module_System" title="Java Platform Module System">Modules</a></li> <li><a href="/wiki/Java_applet" title="Java applet">applets</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Major third-party<br />technologies</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Eclipse_(software)" title="Eclipse (software)">Eclipse</a></li> <li><a href="/wiki/GNU_Classpath" title="GNU Classpath">GNU Classpath</a></li> <li><a href="/wiki/Hibernate_(framework)" title="Hibernate (framework)">Hibernate</a></li> <li><a href="/wiki/Spring_Framework" title="Spring Framework">Spring</a></li> <li><a href="/wiki/Google_Web_Toolkit" title="Google Web Toolkit">GWT</a></li> <li><a href="/wiki/IcedTea" title="IcedTea">IcedTea</a></li> <li><a href="/wiki/Jazelle" title="Jazelle">Jazelle</a></li> <li><a href="/wiki/Apache_Struts" title="Apache Struts">Struts</a></li> <li><a href="/wiki/Oracle_TopLink" title="Oracle TopLink">TopLink</a></li> <li><a href="/wiki/WildFly" title="WildFly">WildFly</a></li> <li><a href="/wiki/Blackdown_Java" title="Blackdown Java">blackdown</a></li> <li><a href="/wiki/Apache_Harmony" title="Apache Harmony">harmony</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">History</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Java_version_history" title="Java version history">Java version history</a></li> <li><a href="/wiki/Java_Community_Process" title="Java Community Process">Java Community Process</a></li> <li><a href="/wiki/Sun_Microsystems" title="Sun Microsystems">Sun Microsystems</a></li> <li><a href="/wiki/Free_Java_implementations" title="Free Java implementations">Free Java implementations</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/List_of_JVM_languages" title="List of JVM languages">JVM languages</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Java_(programming_language)" title="Java (programming language)">Java</a></li> <li><a href="/wiki/BeanShell" title="BeanShell">BeanShell</a></li> <li><a href="/wiki/Clojure" title="Clojure">Clojure</a></li> <li><a href="/wiki/Groovy_(programming_language)" class="mw-redirect" title="Groovy (programming language)">Groovy</a></li> <li><a href="/wiki/JRuby" title="JRuby">JRuby</a></li> <li><a href="/wiki/Jython" 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title="Sun Microsystems Laboratories">Sun Microsystems Laboratories</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">People</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/James_Gosling" title="James Gosling">James Gosling</a></li> <li><a href="/wiki/Arthur_van_Hoff" title="Arthur van Hoff">Arthur van Hoff</a></li> <li><a href="/wiki/Urs_H%C3%B6lzle" title="Urs Hölzle">Urs Hölzle</a></li> <li><a href="/wiki/Patrick_Naughton" title="Patrick Naughton">Patrick Naughton</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><td class="navbox-abovebelow" colspan="3"><div><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" 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