Non-Clustered Session Management: File System

Non-Clustered Session Management: File System
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Enabling File System Sessions
Configuring File System Session Properties

Enabling File System Sessions

When using the Jetty distribution, you will first need to enable the session-store-file module for your Jetty base using the --add-to-start argument on the command line.

$ java -jar ../start.jar --create-startd
INFO : Base directory was modified

$ java -jar ../start.jar --add-to-start=session-store-file
INFO  : server          transitively enabled, ini template available with --add-to-start=server
INFO  : sessions        transitively enabled, ini template available with --add-to-start=sessions
INFO  : session-store-file initialized in ${jetty.base}/start.d/session-store-file.ini
MKDIR : ${jetty.base}/sessions
INFO  : Base directory was modified

Doing this enables the File System Session module and any dependent modules or files needed for it to run on the server. The example above is using a fresh ${jetty.base} with nothing else enabled.

When the --add-to-start argument was added to the command line, it enabled the the session-store-file module as well as the sessions and server modules, which are required for the File System session management to operate. Additionally a ${jetty.base}/sessions directory was created. By default Session files will be saved to this directory.

In addition to adding these modules to the classpath of the server, several ini configuration files were added to the ${jetty.base}/start.d directory.

Configuring File System Session Properties

Opening start.d/session-store-file.ini will show a list of all the configurable options for the file system session module:

# ---------------------------------------
# Module: session-store-file
# Enables session persistent storage in files.
# ---------------------------------------
--module=session-store-file

jetty.session.file.storeDir=${jetty.base}/sessions
#jetty.session.file.deleteUnrestorableFiles=false
#jetty.session.savePeriod.seconds=0

jetty.session.storeDir: This defines the location for storage of Session files.
jetty.session.file.deleteUnrestorableFiles: Boolean. If set to true, unreadable files will be deleted: this is useful to prevent repeated logging of the same error when the scavenger periodically (re-) attempts to load the corrupted information for a session in order to expire it.
jetty.session.savePeriod.seconds=0: By default whenever the last concurrent request leaves a session, that session is always persisted via the SessionDataStore, even if the only thing that changed on the session is its updated last access time. A non-zero value means that the SessionDataStore will skip persisting the session if only the access time changed, and it has been less than savePeriod seconds since the last time the session was written.
Note
Configuring savePeriod is useful if your persistence technology is very slow/costly for writes. In a clustered environment, there is a risk of the last access time of the session being out-of-date in the shared store for up to savePeriod seconds. This allows the possibility that a node may prematurely expire the session, even though it is in use by another node. Thorough consideration of the maxIdleTime of the session when setting the savePeriod is imperative - there is no point in setting a savePeriod that is larger than the maxIdleTime.

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