Skip to main content

Notice: This Wiki is now read only and edits are no longer possible. Please see: for the plan.

Jump to: navigation, search

Hudson-ci/features/Restart Within Hudson

Restart Within Hudson

Configuration changes that require Hudson restart to take effect should provide a Restart link or button.

Unfortunately, the CLI restart or soft-restart methods, which call Hudson.restart and Hudson.safeRestart, respectively, don't handle many of the necessary use cases by default. A Hudson restart link based on these methods would too often fail. It is one thing to leave an opening for plugins to implement, but quite another to depend on the kindness of plugins for basic Hudson operations. The default Lifecycle implementation needs to be in some sense universal, even if it requires the cooperation of system administrators.


In the following, "correct restart" means restart specifically tailored to the environment in which the Hudson instance is running. "System administrator" is a person who provisions and deploys the Hudson instance. "Hudson admin" is a person with admin privileges in Hudson. Sometimes these are the same people; sometimes not.

  • The current Lifecycle API must be preserved, for compatibility with existing plugin extensions. The new default mechanism will only be invoked if the hudson.lifecycle system property is not specified.
  • It must be possible for a system administrator to preconfigure Hudson for correct restart. This is particularly important for "no-admin" uses of Hudson.
  • Restart must require Hudson admin privileges (ACL.SYSTEM).

Design Approach

There are two ways to provide a correct restart. The first is to add a plugin that extends hudson.lifecycle.Lifecycle and add the hudson.lifecycle Java property to the command line that launches Hudson. This option was also available in previous releases. The second is by using a new feature, Restart Command, that allows restart with OS scripts. We illustrate it with the simplest possible Lifecycle and supporting Hudson launch script.

The Restart Command allows a system administrator to specify a command or provide a script during Hudson startup.

Just Exit Lifecycle

The Just Exit Lifecycle Plugin implements a Lifecycle whose restart method just calls System.exit(0). About as trivial a plugin as one can imagine, but it is enough to enable the Restart button in the plugin manager. (It is may not be a good idea to use this when running Hudson in a server with multiple applications in the same JVM, but there aren't many other good ideas for restart in this environment, suggesting the environment, itself, may not be a good idea.)

Supporting Shell Script

Obviously, Just Exit only does the stop part of restart. To do the start part, we recommend always launching Hudson with a script that will automatically restart it when it exits, for example, when it is stopped by the kill command. For example,

export HUDSON_WAR=<path-to-Hudson-WAR>
export HUDSON_HOME=<path-to-Hudson-home>
if [ -e "$HUDSON_HOME/plugins/just-exit-lifecycle.hpi" ]
  export LIFECYCLE="-Dhudson.lifecycle=org.hudsonci.plugins.justexit.JustExitLifecycle"

while :

    if [ "x$1" == "x-d" ]
        java $LIFECYCLE -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=8000 -jar $HUDSON_WAR &
        java $LIFECYCLE -jar $HUDSON_WAR &

    trap "break" SIGINT SIGTERM
    # receiving trapped signal makes wait return
    # with exit status >= 128, then trap executes
    wait ${!}
    sleep 1
    echo "Restarting Hudson"

echo "Killing child process"
pkill -P "$$"

When the script is run, it executes Hudson in a loop. Thus, it implements the 'start' part of restart. Hudson will restart if it exits or is killed. (To actually kill Hudson, kill the script that launched it.)

This technique is simple and can be adapted to a failsafe environment by ensuring the alternate server doesn't start up during the restart.

Restart Command

Correct restart is a multi-dimensional problem, different for each OS, service implementation and container (Tomcat, Jetty, GlassFish, etc.). The Lifecycle extension point is not well suited for multi-dimensional invocation, e.g., the OS is X AND the container is Y and (the container does not support single application restart OR the application name/war file location in the container is Z). While certain tricks, like replacing the Hudson WAR file, work to restart the application in many containers, to cover all the possibilites, Lifecycle would need an extension for every possible combination.

Yet, every system administrator already knows or can easily discover a command or script to restart any running Hudson instance. The best and most likely to be correct restart mechanism would leverage those commands/scripts and not try to replace it with Java code. The feature described below provides a generic Lifecycle that does.

Two new ways are provided for the system administrator to configure correct restart:

  • by providing a hudson-restart file in the $HUDSON_HOME provisioned for the Hudson instance or
  • by specifying a restart command on the command line when Hudson is invoked.


In a nutshell, restart within Hudson will invoke a system administrator--supplied command.

Since the command is presumed to restart Hudson, it may not return at all. If it does return, it is expected to return successfully. If the restart command fails, restart will fail.

If the restart command is not specified, the existing default Lifecycle mechanism will be invoked.

If the hudson.lifecycle system property is specified, the restart command, if any, will not be used.

Default Restart Script

To allow system administrators to pre-configure Hudson for correct restart, if a restart script is present in HUDSON_HOME the initial value of the restart command will be set to invoke the script. The script must be named hudson_restart[.extension].

The script or program may have an extension, e.g., .bat on Windows or .sh, .bash, .py, etc. on Unix, but it doesn't matter what it is; in all cases, it will be invoked as a program.

The script must be executable.

The script should be specific to the environment in which the HUDSON_HOME is used.

Restart System Property

Even if a restart script is present in HUDSON_HOME, a system administrator may change the restart command to do something else, effectively ignoring the script, using the command line option:


The value of the hudson.restart system property will be used to initialize the restart command. The correct order of initialization is:

  • If -Dhudson.restart is specified, use that.
  • Otherwise, if a restart script is present, use a command that invokes the script.
  • Otherwise, the restart command is not specified.


A new lifecycle, hudson.lifecycle.RestartCommandLifecycle, will be added to Hudson.

hudson.lifecycle.Lifecycle will be modified to use the RestartCommandLifecycle for restart if:

  • a restart script or command has been specified, and
  • the hudson.lifecycle system property is not defined.

The implementation will log a warning message if hudson.lifecycle has been specified and a restart script or command have been provided.

Restart Links or Buttons

Restart links should not be shown unless Lifecycle.get().canRestart() returns true. Otherwise, a message like "Restart required for changes to take effect" should be displayed.

A restart link should show the single word Restart and should call Hudson.safeRestart.

Plugin Manager

The Plugin Manager will show a restart link if a) a plugin is updated or a plugin is loaded that requires restart, and b) if Lifecycle.get().canRestart() returns true.

Back to the top