Invocation

This page describes how to invoke a daemon written using the Daemon library. Specifically, it documents the built-in commands and their options.

The built-in commands allow you to start, shut down, and check daemon instances. (All other commands are sent to the running daemon process, where they will be handled by the handleCommand() method of the IDaemon subclass.)

In the syntax examples, jarname is the jar file that contains your daemon, and options refers to standard options.

Options

The following options can be used with the built-in commands.

--instance=instanceName

Apply the command to the instance called instanceName. If this option is not used, then the default instance name (as returned by the getDefaultInstanceName() method of the DaemonController subclass) is used.

--stdoutLog=filename

Use the given filename as the stdout log (the log file that captures the stdout and stderr of the daemon.)

--jvmOptions=options

Use the given JVM options when starting the daemon process.

Built-in Commands

These are the built-in commands. (In the synopses below, options refers to the options described in the previous section.)

java -jar jarname options start

Start a daemon instance.

java -jar jarname options shutdown

Shut down a daemon instance.

java -jar jarname options check

Check whether a daemon instance is running.

java -jar jarname options poke

Check whether a daemon instance is running, and restart it if it is not running. This command is meant to be run periodically (e.g., from a cron job) to restart the daemon in the event of a crash, reboot, etc.

Examples

Here are some examples. The examples assume that your application is a single executable jar file called myApp.jar.

java -jar myApp.jar start

Start the default instance of the daemon.

java -jar myApp.jar shutdown

Shut down the default instance of the daemon.

java -jar myApp.jar poke

Check whether the default instance of the daemon is running, and if not, start it.

java -jar myApp.jar --instance=foobar start

Start an instance of the daemon using "foobar" as the instance name. You can have any number of instances of the same daemon running as long as they all have different instance names.

java -jar myApp.jar --instance=foobar shutdown

Shut down the instance of the daemon that has the instance name "foobar".

java -jar myApp.jar --jvmOptions="-Xmx1024m -XX:-OmitStackTraceInFastThrow" start

Start the default instance of the daemon, specifying some JVM options.