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| </p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="session-management"></a>Chapter 10. Session Management</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="session-management.html#jetty-sessions-architecture">Session Architecture</a></span></dt><dt><span class="section"><a href="sessions-details.html">Session Components</a></span></dt><dt><span class="section"><a href="session-configuration-housekeeper.html">The SessionIdManager and the Housekeeper</a></span></dt><dt><span class="section"><a href="session-configuration-sessioncache.html">The L1 Session Cache</a></span></dt><dt><span class="section"><a href="configuring-sessions-memory.html">Non-Persistent Sessions</a></span></dt><dt><span class="section"><a href="configuring-sessions-file-system.html">Persistent Sessions: File System</a></span></dt><dt><span class="section"><a href="configuring-sessions-jdbc.html">Persistent Sessions: JDBC</a></span></dt><dt><span class="section"><a href="configuring-sessions-mongo.html">Persistent Sessions: MongoDB</a></span></dt><dt><span class="section"><a href="configuring-sessions-infinispan.html">Persistent Sessions: Inifinspan</a></span></dt><dt><span class="section"><a href="configuring-sessions-hazelcast.html">Persistent Sessions: Hazelcast</a></span></dt><dt><span class="section"><a href="configuring-sessions-gcloud.html">Persistent Sessions: Google Cloud DataStore</a></span></dt><dt><span class="section"><a href="session-configuration-memcachedsessiondatastore.html">Persistent Sessions: The L2 Session Data Cache</a></span></dt><dt><span class="section"><a href="sessions-usecases.html">Session Use Cases</a></span></dt></dl></div><p>Sessions are a concept within the Servlet api which allow requests to store and retrieve information across the time a user spends in an application. |
| Choosing the correct session manager implementation is an important consideration for every application as each can fit and perform optimally in different situations. |
| If you need a simple in-memory session manager that can persist to disk then session management using the local file system can be a good place to start. |
| If you need a session manager that can work in a clustered scenario with multiple instances of Jetty, then the JDBC session manager can be an excellent option. |
| Jetty also offers more niche session managers that leverage backends such as MongoDB, Inifinispan, or even Google’s Cloud Data Store.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="jetty-sessions-architecture"></a>Session Architecture</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="section"><a href="session-management.html#_changes_in_session_architecture">Changes in Session Architecture</a></span></dt><dt><span class="section"><a href="session-management.html#_session_architecture_hierarchy">Session Architecture Hierarchy</a></span></dt><dt><span class="section"><a href="session-management.html#_configuring_sessions_in_the_jetty_distribution">Configuring Sessions in the Jetty Distribution</a></span></dt></dl></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_changes_in_session_architecture"></a>Changes in Session Architecture</h3></div></div></div><p>The architecture of Session Management Jetty changed significantly in Jetty 9.4. |
| These changes have resulted in Sessions not only being easier to configure but making them much more pluggable for various technologies.</p><p>In previous versions of Jetty, users were required to configure a separate <code class="literal">SessionIdManager</code> for each kind of session clustering technology being implemented (JDBC, MongoDB..etc.). |
| In Jetty 9.4, there is now a single <code class="literal">SessionIdManager</code> implementation which works across all types of session clustering technologies. |
| Likewise, prior to Jetty 9.4 there were several different instances of the <code class="literal">SessionManager</code> class. |
| Instead of a single <code class="literal">SessionManager</code> though, it has been done away with entirely, with most of it’s functionality moved to the <code class="literal">SesssionHandler</code> class. |
| Additionally, Jetty 9.4 introduced the concepts of a <code class="literal">SessionCache</code> and an associated <code class="literal">SessionDataStore</code> (both explained below).</p><p>Finally, Session scavenging has been re-worked. |
| Where previously each <code class="literal">SessionManager</code> instance would periodically scan the in-memory (or clustered) sessions for expired sessions, there is now a single generic scavenger thread which instructs the <code class="literal">SessionHandler</code> to clean up expired sessions. |
| Session expiration has been changed to use a much more efficient timer-based mechanism that avoids constant iteration over all current sessions in memory by the scavenger.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_session_architecture_hierarchy"></a>Session Architecture Hierarchy</h3></div></div></div><p>Each Jetty instance has a singular <code class="literal">SessionIdManager</code> to handle all session requests, regardless of clustering technology. |
| For each context on the server there is one (1) <code class="literal">SessionCache</code> which contains all of the Session objects for the given context. |
| The benefit of the <code class="literal">SessionCache</code> is to ensure that simultaneous requests accessing the same Session Id in the same context always operate on the same Session object. |
| The SessionCache implementation supplied with the Jetty distribution does just that: keeps Session objects in memory so that they can be shared between simultaneous requests. |
| However, it is possible to provide your own implementation that never shares Session objects should you require it.</p><p>Where the <code class="literal">SessionCache</code> handles Session information, Session data is stored in a <code class="literal">SessionDataStore</code> that is specific to the clustering technology being implemented. |
| There is only one (1) <code class="literal">SessionDataStore</code> per <code class="literal">SessionCache</code>.</p><p>Visually the session architecture can be represented like this:</p><div class="informalfigure"><div class="mediaobject"><img src="images/SessionsHierarchy.png" alt="SessionsHierarchy"></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_configuring_sessions_in_the_jetty_distribution"></a>Configuring Sessions in the Jetty Distribution</h3></div></div></div><p>Configuring session management involves selecting a <a class="link" href="startup-modules.html" title="Managing Startup Modules">module</a> for the desired type of <a class="link" href="session-configuration-sessioncache.html" title="The L1 Session Cache">session caching</a> behavior, and a module for the type of session persistence.</p><p>Jetty provides two different session caches: the <code class="literal">DefaultSessionCache</code> which holds sessions in memory, and the <code class="literal">NullSessionCache</code> which does not. |
| There is more information on both of these types of session caching and the circumstances which would lead you to select one or the other in the <a class="link" href="sessions-details.html" title="Session Components">Session Components</a> section, and more information on the configuration options of each in <a class="link" href="session-configuration-sessioncache.html" title="The L1 Session Cache">the L1 Session Cache</a> section.</p><p>For session persistence, Jetty provides a number of different implementations from which to choose including <a class="link" href="configuring-sessions-memory.html" title="Non-Persistent Sessions">non-persistence</a>, <a class="link" href="configuring-sessions-file-system.html" title="Persistent Sessions: File System">local file storage</a>, clustered technologies such as <a class="link" href="configuring-sessions-jdbc.html" title="Persistent Sessions: JDBC">JDBC</a>, <a class="link" href="configuring-sessions-mongo.html" title="Persistent Sessions: MongoDB">MongoDB</a>, <a class="link" href="configuring-sessions-infinispan.html" title="Persistent Sessions: Inifinspan">Inifinispan</a>, <a class="link" href="configuring-sessions-gcloud.html" title="Persistent Sessions: Google Cloud DataStore">Google Cloud Datastore</a>, and <a class="link" href="configuring-sessions-hazelcast.html" title="Persistent Sessions: Hazelcast">Hazelcast</a>.</p><p>Depending on your persistence technology, to enhance performance, you may want to use an L2 cache for session data, in which case Jetty provides the <a class="link" href="session-configuration-memcachedsessiondatastore.html" title="Persistent Sessions: The L2 Session Data Cache">memcached L2 session data cache</a>.</p></div></div></div><script type="text/javascript"> |
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