Persistent Sessions: Hazelcast

Persistent Sessions: Hazelcast
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Enabling Hazelcast Sessions
Configuring Hazelcast Remote Properties
Configuring Embedded Hazelcast Clustering
Configuring Hazelcast Embedded Properties

Enabling Hazelcast Sessions

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

$ java -jar ../start.jar --create-startd
MKDIR : ${jetty.base}/start.d
INFO  : Base directory was modified

$ java -jar ../start.jar --add-to-start=session-store-hazelcast-remote

ALERT: There are enabled module(s) with licenses.
The following 1 module(s):
 + contains software not provided by the Eclipse Foundation!
 + contains software not covered by the Eclipse Public License!
 + has not been audited for compliance with its license

 Module: session-store-hazelcast-remote
  + Hazelcast is an open source project hosted on Github and released under the Apache 2.0 license.
  + https://hazelcast.org/
  + http://www.apache.org/licenses/LICENSE-2.0.html

Proceed (y/N)? y
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-hazelcast-remote initialized in ${jetty.base}/start.d/session-store-hazelcast-remote.ini
MKDIR : /Users/admin/mvn-repo/com/hazelcast/hazelcast/3.8.2
DOWNLD: https://repo1.maven.org/maven2/com/hazelcast/hazelcast/3.8.2/hazelcast-3.8.2.jar to /Users/admin/mvn-repo/com/hazelcast/hazelcast/3.8.2/hazelcast-3.8.2.jar
MKDIR : ${jetty.base}/lib/hazelcast
COPY  : /Users/admin/mvn-repo/com/hazelcast/hazelcast/3.8.2/hazelcast-3.8.2.jar to ${jetty.base}/lib/hazelcast/hazelcast-3.8.2.jar
COPY  : /Users/admin/mvn-repo/com/hazelcast/hazelcast-client/3.8.2/hazelcast-client-3.8.2.jar to ${jetty.base}/lib/hazelcast/hazelcast-client-3.8.2.jar
INFO  : Base directory was modified

Doing this enables the remote Hazelcast 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. Because Hazelcast is not a technology provided by the Eclipse Foundation, users are prompted to assent to the licenses of the external vendor (Apache in this case).

When the --add-to-start argument was added to the command line, it enabled the the session-store-hazelcast-remote module as well as the sessions and server modules, which are required for Hazelcast session management to operate. It also downloaded the needed Hazelcast-specific jar files and created a directory named ${jetty.base}/lib/hazelcast/ to house them.

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

Note
If you have updated versions of the jar files automatically downloaded by Jetty, you can place them in the associated ${jetty.base}/lib/ directory and use the --skip-file-validation=<module name> command line option to prevent errors when starting your server.

Configuring Hazelcast Remote Properties

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

# ---------------------------------------
# Module: session-store-hazelcast-remote
# Enables session data store in a remote Hazelcast Map
# ---------------------------------------
--module=session-store-hazelcast-remote

#jetty.session.hazelcast.mapName=jetty_sessions
#jetty.session.hazelcast.onlyClient=true
#jetty.session.hazelcast.configurationLocation=
#jetty.session.gracePeriod.seconds=3600
#jetty.session.savePeriod.seconds=0

jetty.session.hazelcast.mapName: Name of the Map in Hazelcast where sessions will be stored.
jetty.session.hazelcast.onlyClient: Hazelcast instance will be configured in client mode
jetty.session.hazelcast.configurationLocation: Path to an an Hazelcast xml configuration file
jetty.session.gracePeriod.seconds: Amount of time, in seconds, to wait for other nodes to be checked to verify an expired session is in fact expired throughout the cluster before closing 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.

Configuring Embedded Hazelcast Clustering

During testing, it can be helpful to run an in-process instance of Hazelcast. To enable this you will first need to enable the session-store-hazelcast-embedded module for your Jetty base using the --add-to-start argument on the command line.

$ java -jar ../start.jar --create-startd
MKDIR : ${jetty.base}/start.d
INFO  : Base directory was modified
$ java -jar ../start.jar --add-to-start=session-store-hazelcast-embedded

ALERT: There are enabled module(s) with licenses.
The following 1 module(s):
 + contains software not provided by the Eclipse Foundation!
 + contains software not covered by the Eclipse Public License!
 + has not been audited for compliance with its license

 Module: session-store-hazelcast-embedded
  + Hazelcast is an open source project hosted on Github and released under the Apache 2.0 license.
  + https://hazelcast.org/
  + http://www.apache.org/licenses/LICENSE-2.0.html

Proceed (y/N)? y
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-hazelcast-embedded initialized in ${jetty.base}/start.d/session-store-hazelcast-embedded.ini
MKDIR : /Users/admin/mvn-repo/com/hazelcast/hazelcast/3.8.2
DOWNLD: https://repo1.maven.org/maven2/com/hazelcast/hazelcast/3.8.2/hazelcast-3.8.2.jar to /Users/admin/mvn-repo/com/hazelcast/hazelcast/3.8.2/hazelcast-3.8.2.jar
MKDIR : ${jetty.base}/lib/hazelcast
COPY  : /Users/admin/mvn-repo/com/hazelcast/hazelcast/3.8.2/hazelcast-3.8.2.jar to ${jetty.base}/lib/hazelcast/hazelcast-3.8.2.jar
COPY  : /Users/admin/mvn-repo/com/hazelcast/hazelcast-client/3.8.2/hazelcast-client-3.8.2.jar to ${jetty.base}/lib/hazelcast/hazelcast-client-3.8.2.jar

Doing this enables the embedded Hazelcast 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. Because Hazelcast is not a technology provided by the Eclipse Foundation, users are prompted to assent to the licenses of the external vendor (Apache in this case).

When the --add-to-start argument was added to the command line, it enabled the the session-store-hazelcast-embedded module as well as the sessions and server modules, which are required for Hazelcast session management to operate. It also downloaded the needed Hazelcast-specific jar files and created a directory named ${jetty.base}/lib/hazelcast/ to house them.

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

Configuring Hazelcast Embedded Properties

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

# ---------------------------------------
# Module: session-store-hazelcast-embedded
# Enables session data store in an embedded Hazelcast Map
# ---------------------------------------
--module=session-store-hazelcast-embedded

#jetty.session.hazelcast.mapName=jetty_sessions
#jetty.session.hazelcast.configurationLocation=
#jetty.session.gracePeriod.seconds=3600
#jetty.session.savePeriod.seconds=0

jetty.session.hazelcast.mapName: Name of the Map in Hazelcast where sessions will be stored.
jetty.session.gracePeriod.seconds: Amount of time, in seconds, to wait for other nodes to be checked to verify an expired session is in fact expired throughout the cluster before closing it.
jetty.session.hazelcast.configurationLocation: Path to an an Hazelcast xml configuration file
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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