basic-algorithm.html

<!DOCTYPE html>  <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <meta charset="UTF-8" /> <meta name="viewport" content="width=device-width, initial-scale=1.0" /> <meta name="Date-Revision-yyyymmdd" content="20160415" /> <meta http-equiv="Content-Language" content="en" /> <title>Apache Omid – Basic Transaction Algorithm</title> <link rel="stylesheet" href="./css/apache-maven-fluido-1.5.min.css" /> <link rel="stylesheet" href="./css/site.css" /> <link rel="stylesheet" href="./css/print.css" media="print" /> <script type="text/javascript" src="./js/apache-maven-fluido-1.5.min.js"></script> </head> <body class="topBarEnabled"> <div id="topbar" class="navbar navbar-fixed-top "> <div class="navbar-inner"> <div class="container" style="width: 100%;"><div class="nav-collapse"> <ul class="nav"> <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown">Home <b class="caret"></b></a> <ul class="dropdown-menu"> <li> <a href="index.html" title="Overview">Overview</a> </li> <li> <a href="license.html" title="License">License</a> </li> </ul> </li> <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown">Download <b class="caret"></b></a> <ul class="dropdown-menu"> <li> <a href="https://bintray.com/yahoo/maven/omid" title="Download Omid">Download Omid</a> </li> <li> <a href="https://bintray.com/yahoo/maven/omid" title="Bintray Repository">Bintray Repository</a> </li> </ul> </li> <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown">User Guide & API <b class="caret"></b></a> <ul class="dropdown-menu"> <li> <a href="quickstart.html" title="Quickstart">Quickstart</a> </li> <li> <a href="basic-examples.html" title="API and Code Examples">API and Code Examples</a> </li> </ul> </li> <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown">Technical Docs <b class="caret"></b></a> <ul class="dropdown-menu"> <li> <a href="basic-concepts.html" title="Basic Concepts">Basic Concepts</a> </li> <li> <a href="omid-components.html" title="Omid Components">Omid Components</a> </li> <li> <a href="basic-algorithm.html" title="Basic Algorithm">Basic Algorithm</a> </li> <li> <a href="client-failure-management.html" title="Management of Client Failures">Management of Client Failures</a> </li> <li> <a href="http://yahoohadoop.tumblr.com/tagged/HBase" title="Blog Entries">Blog Entries</a> </li> </ul> </li> <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown">Contribute <b class="caret"></b></a> <ul class="dropdown-menu"> <li> <a href="https://git-wip-us.apache.org/repos/asf/incubator-omid.git" title="Source Code">Source Code</a> </li> <li> <a href="https://issues.apache.org/jira/browse/Omid" title="JIRA">JIRA</a> </li> <li> <a href="mailing-lists.html" title="Mailing Lists">Mailing Lists</a> </li> <li> <a href="coding-guide-and-style.html" title="Coding Guide and Style">Coding Guide and Style</a> </li> </ul> </li> <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown">Project Reports <b class="caret"></b></a> <ul class="dropdown-menu"> <li class="dropdown-submenu"> <a href="project-info.html" title="Project Information">Project Information</a> <ul class="dropdown-menu"> <li> <a href="dependency-convergence.html" title="Dependency Convergence">Dependency Convergence</a> </li> <li> <a href="dependency-info.html" title="Dependency Information">Dependency Information</a> </li> <li> <a href="dependency-management.html" title="Dependency Management">Dependency Management</a> </li> <li> <a href="distribution-management.html" title="Distribution Management">Distribution Management</a> </li> <li> <a href="index.html" title="About">About</a> </li> <li> <a href="license.html" title="Licenses">Licenses</a> </li> <li> <a href="modules.html" title="Project Modules">Project Modules</a> </li> <li> <a href="plugin-management.html" title="Plugin Management">Plugin Management</a> </li> <li> <a href="plugins.html" title="Plugins">Plugins</a> </li> <li> <a href="team-list.html" title="Team">Team</a> </li> <li> <a href="source-repository.html" title="Source Code Management">Source Code Management</a> </li> <li> <a href="project-summary.html" title="Summary">Summary</a> </li> </ul> </li> </ul> </li> </ul> <form id="search-form" action="https://www.google.com/search" method="get" class="navbar-search pull-right" > <input value="omid.incubator.apache.org" name="sitesearch" type="hidden"/> <input class="search-query" name="q" id="query" type="text" /> </form> <script type="text/javascript" src="https://cse.google.com/brand?form=search-form"></script> <ul class="nav pull-right"><li> <a href="https://twitter.com/apacheomid" class="twitter-follow-button" data-show-count="true" data-align="right" data-size="large" data-show-screen-name="true" data-lang="en">Follow apacheomid</a> <script type="text/javascript">!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs");</script> </li></ul> </div> </div> </div> </div> <div class="container"> <div id="banner"> <div class="pull-left"> <a href="./" id="bannerLeft"> <img src="images/omid-logo.png" alt="Omid" width="200"/> </a> </div> <div class="pull-right"> <a href="http://incubator.apache.org/" id="bannerRight"> <img src="http://incubator.apache.org/images/egg-logo2.png" alt="Apache Incubator" width="200"/> </a> </div> <div class="clear"><hr/></div> </div> <div id="breadcrumbs"> <ul class="breadcrumb"> <li id="projectVersion">Version: 0.8.1.37-SNAPSHOT </li> <li id="publishDate" class="pull-right">Last Published: 2016-04-15</li> </ul> </div> <div id="bodyColumn" > <h1>Basic Transaction Algorithm</h1> <p>A simplified version of the algorithm for performing transactional operations in a non-faulty scenario is depicted in the following figure:</p> <p><img src="images/basic-alg.png" alt="Basic algorithm for managing transactions" /></p> <p>Initially, a user application (not shown in the figure for the sake of simplicity) starts a new transaction using the Transactional Client API, which in turn acquires a start timestamp from the TSO.</p> <p>Then, the user application logic, also through the Transactional Client API, performs a series of read and write operations in the snapshot provided by the transactional context recently acquired.</p> <p>In the case of reads, if the cells read have shadow cells and their value is in the snapshot for the transaction, their value is taken directly. If the commit timestamp is missed in the shadow cell, the Transactional Client will try to find it in the commit table. If the commit timestamp is found in there and the cell value is in the snapshot, the cell value is taken. However, if the commit timestamp is missed, the shadow cell is re-checked. If it still does not exist, the cell is ignored and another version that matches the snapshot will be retrieved from the datastore.</p> <p>When the application commits the transaction, the Transactional Client contacts the TSO in order to check the possible conflicts of the transaction. If the writeset does not conflict with other concurrent transactions, the transaction is committed, the TSO updates the commit table and replies back to the Transactional Client, which in turn, returns the control to the user application.</p> <p>Finally, the Transactional Client, on receiving the commit acknowledgement, updates the shadow cells with the required data. After this, it can also remove safely the entry added by the TSO in the commit table.</p> <p>In case the TSO detects conflicts, the transaction is aborted (not shown in the figure), the Transactional Client will clean up the data written to the datastore, and will inform the user application throwing a rollback exception.</p> </div> </div> <hr/> <footer> <div class="container"> <div class="row"> <p >Copyright © 2011–2016 <a href="http://www.apache.org">Apache Software Foundation</a>. All rights reserved. </p> </div> <p id="poweredBy" class="pull-right"> <a href="http://maven.apache.org/" title="Maven" class="builtBy"> <img class="builtBy" alt="Maven" src="http://maven.apache.org/images/logos/maven-feather.png" /> </a> </p> </div> </footer> </body> </html>

basic-algorithm.html (171 lines of code) (raw):