#Session Pool

Session Pool is a simple JAR application. The main purpose of this module is to start, manage and communicate with an application instance. It connects to a Cluster Server via a WebSocket and it is always connected to all Cluster Servers in the Cluster. It is not desired that there is a connection problem between a Session Pool and a Cluster Server and this kind of problem should be resolved ASAP.

Unlike Cluster Server, Session Pool is stateful. When a Session Pool encounters a fatal error which leads to termination, all of the application instance processes that this Session Pool has created will be terminated as well.

Session Pool can be configured using the webswing-sessionpool.properties file. The table below describes the standard and supported properties used by Session Pool.

Cluster Session Pool handles everything related to the application instance, therefore it needs access too application binaries, libraries, fonts and application configuration (webswing-app.config).

Cluster Session Pool installation includes:

• webswing.war
• webswing-app.config
• webswing-sessionpool.properties
• sessionpool.bat / sessionpool.sh
• application jar binaries and libraries
• fonts

Here is an example of a webswing-app.config file:

{
    "/webswing-demo" : {
        "allowUpload" : true,
        "allowDownload" : true,
        "isolatedFs" : true,
        "sessionLogging" : false,
        "allowJsLink" : true,
        "javaFx" : true,
        "javaFxClassPathEntries" : [ "${webswing.rootDir}/apps/javafx/*.jar" ],
        "homeDir" : "${webswing.rootDir}/apps/WebswingDemo",
        "theme" : "Murrine",
        "directdraw" : true,
        "debug" : true,
        "jreExecutable" : "${java.home}/bin/java",
        "javaVersion" : "${java.version}",
        "launcherType" : "Desktop",
        "launcherConfig" : {
        "mainClass" : "org.webswing.demo.WebswingDemoApp"
        },
        "swingSessionTimeout" : 300,
        "timeoutIfInactive" : false,
        "allowDelete" : true,
        "allowAutoDownload" : true,
        "allowLocalClipboard" : true,
        "allowServerPrinting" : false,
        "dockMode" : "ALL",
        "allowStatisticsLogging" : true,
        "testMode" : false,
        "jsLinkWhitelist" : [ "*" ],
        "transferDir" : "${user}/upload",
        "clearTransferDir" : true,
        "sessionLogFileSize" : "${webswing.sessionLog.size:-10MB}",
        "transparentFileSave" : true,
        "sessionLogMaxFileSize" : "${webswing.sessionLog.maxSize:-1000MB}",
        "transparentFileOpen" : true,
        "fontConfig" : { },
        "classPathEntries" : [ "*.jar" ]
    }
}

#Drain mode

Drain mode is useful when you want to shutdown a Session Pool or do some maintenance and you don't want to interfere with running sessions on that Session Pool. Drain mode will simply not allow to connect any more sessions. Note that drain mode does not automatically shutdown the Session Pool after all sessions finish. You can put Session Pool into drain mode in Admin Console.

#Session Pool resilience

When session pool crashes, all sessions running on this session pool are lost and cannot be recovered. To be able to recover running sessions you can use the following configuration in webswing-sessionpool.properties.

# enables instance resilience - session pool can recover connection to app instance processes after restart
# NOTE: recovered session pool MUST have the same sessionpool.id
sessionpool.instanceResilience.enabled = true
# path where instance descriptors and process streams are stored
sessionpool.instanceResilience.descriptors.dir = descriptors
# how long should instance wait for session pool to become available again after session pool goes down (in seconds)
sessionpool.instanceResilience.heartbeatTimeout.instance = 60

To be able to recover the sessions Webswing redirects the process I/O streams to files. Stream files with process/session descriptors are stored in descriptors directory. You can also setup the timeout how long will the session wait to be recovered after session pool crashes. Note that the restarted session pool must have the same id as the previous session pool that crashed, otherwise sessions cannot be recovered.