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Documenting the self-restarting process

pull/37/merge
Kohsuke Kawaguchi 2014-04-01 13:33:01 -07:00
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@ -65,6 +65,17 @@ The success or failure of these operations will be recorded in the event log.
The `<download>` element in the configuration file also provides an useful building block for a self updating services.
Restarting service from itself
------------------------------
To support self-restarting services, winsw exposes `WINSW_EXECUTABLE` environment variable into the forked process, which refers to the full path of `winsw.exe` that's managing the service.
To restart the service from within, execute `$WINSW_EXECUTABLE restart!`. Note that you are invoking `restart!` command, not `restart` command. This hidden command is a flavor of the `restart` operation,
except that winsw creates another winsw process in a separate process group, and restarts the service from there.
This additional indirection is necessary, because Windows Service Control Manager (SCM) will kill child processes recursively when it stops the service. SCM doesn't provide restart operation
as an atomic operation either, so winsw implements restart by a sequence of stop and start. The 2nd winsw process in a separate process group ensures that winsw can survive this massacre to
execute the start call.
Logging
-------
Winsw supports several different ways to capture stdout and stderr from the process you launch.