session tags

Resin adds a number of additions to the standard session-config tag.

<cookie-domain> configures the host domain to use for sessions, i.e. value of the Domain cookie attributes.

By default, browsers only send cookies back to the exact host which sent them. In some virtual host cases, it makes sense to share the same cookie value for multiple virtual hosts in the same domain. For example, caucho.com might want a single cookie to be used for both gryffindor.caucho.com and slytherin.caucho.com. In this case the cookie-domain would be set to caucho.com.

<resin xmlns="http://caucho.com/ns/resin">
<cluster id="app-tier">

  <host id="caucho.com">
    <host-alias>gryffindor.caucho.com</host-alias>
    <host-alias>slytherin.caucho.com</host-alias>

    <web-app-default>

      <session-config cookie-domain="caucho.com"/>

    </web-app-default>
  </host>

</cluster>
</resin>

<cookie-length> sets the length of the generated cookie value. In some rare cases, the cookie-length might need to be shortened or the cookie-length might be extended to add randomness to the cookie value. For the most part, this value should be left alone.

<cookie-max-age> sets how long the browser should keep the session cookie.

By default, browsers keep cookies as long as they are open. When the browser is restarted, the cookies are dropped. cookie-max-age tells the browser to keep the cookie for a certain time period. Applications can make this time "infinite" by setting a large number.

<cookie-version> sets the version of the cookie spec for sessions.

<ignore-serialization-errors> is used with persistent sessions in certain rare cases where some session data is serializable and other data is not serializable. <ignore-serialization-errors> simply skips session values which do not implement java.io.Serializable when serializing the session.

Session configuration parameters.

Resin adds a number of session-config tags.

By default, both enable-cookies and enable-url-rewriting are true. To force url rewriting, you would create a configuration like:

<web-app id='/'>

  <session-config
   enable-cookies='false'
   enable-url-rewriting='true'/>

</web-app>

The session-timeout and session-max are usually used together to control the number of sessions. Sessions are stored in an LRU cache. When the number of sessions in the cache fills up past session-max, the oldest sessions are recovered. In addition, sessions idle for longer than session-timeout are purged.

<web-app id='/dir'>

  <session-config>
     <!-- 2 hour timeout -->
     <session-timeout>120</session-timeout>
     <session-max>4096</session-max>
  </session-config>

</web-app>

cookie-length is used to limit the maximum length for the session's generated cookie for special situations like WAP devices. Reducing this value reduces the randomness in the cookie and increases the chance of session collisions.

reuse-session-id defaults to true so that Resin can share the session id amongst different web-apps.

The class that corresponds to <session-config> is com.caucho.server.session.SessionManager

<session-max> sets the maximum number of sessions stored in memory for a particular <web-app>. The total number of persisted sessions may be larger.

<save-mode> configures when Resin should save a persistence session during a request. The values are:

In some situations, like redirects, a fast browser can send a request back to Resin before the session is persisted with the after-request save-mode. If the server is configured without sticky sessions, the load balancer might send the request to a different server, which may not get the updated session. In the situation, either the save-mode should be changed to before-headers or sticky sessions should be enabled.

If the save-mode is before-headers, the application should take care to make any session changes before sending data to the browser.

<session-timeout> sets how long a <web-app> should keep an idle session before invalidating it. The value is specified in minutes.