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document a little more the signals handling

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benoitc 2013-06-29 06:39:37 +02:00
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docs/source/signals.rst
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@ -38,3 +38,76 @@ automatically respawned.
- **TERM**, **INT**: Quick shutdown
- **QUIT**: Graceful shutdown
- **USR1**: Reopen the log files
Reload the configuration
========================
the signal HUP can be used to reload the Gunicorn configuration on the
fly.
::
2013-06-29 06:26:55 [20682] [INFO] Handling signal: hup
2013-06-29 06:26:55 [20682] [INFO] Hang up: Master
2013-06-29 06:26:55 [20703] [INFO] Booting worker with pid: 20703
2013-06-29 06:26:55 [20702] [INFO] Booting worker with pid: 20702
2013-06-29 06:26:55 [20688] [INFO] Worker exiting (pid: 20688)
2013-06-29 06:26:55 [20687] [INFO] Worker exiting (pid: 20687)
2013-06-29 06:26:55 [20689] [INFO] Worker exiting (pid: 20689)
2013-06-29 06:26:55 [20704] [INFO] Booting worker with pid: 20704
Sending an **HUP** signal will reload the configuration, start the new
worker processes with a new configuration and gracefully shutdown older
workers. If the application is not preloaded (using the ``--preload``
option), Gunicorn will also load the new version.
Upgrading to a new binary on the fly
====================================
If you need to replace the gunicorn binary with a new one (when
upgrading to a new version or adding/removing server modules), you can
do it without any service downtime - no incoming requests will be
lost.
First, replace old binary with a new one, then send **USR2** signal to the
master process. It renames its .pid file to .oldbin (e.g.
/var/run/gunicorn.pid.oldbin), then executes a new binary,
which in turn starts a new master process and the new worker processes::
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
20844 benoitc 20 0 54808 11m 3352 S 0.0 0.1 0:00.36 gunicorn: master [test:app]
20849 benoitc 20 0 54808 9.9m 1500 S 0.0 0.1 0:00.02 gunicorn: worker [test:app]
20850 benoitc 20 0 54808 9.9m 1500 S 0.0 0.1 0:00.01 gunicorn: worker [test:app]
20851 benoitc 20 0 54808 9.9m 1500 S 0.0 0.1 0:00.01 gunicorn: worker [test:app]
20854 benoitc 20 0 55748 12m 3348 S 0.0 0.2 0:00.35 gunicorn: master [test:app]
20859 benoitc 20 0 55748 11m 1500 S 0.0 0.1 0:00.01 gunicorn: worker [test:app]
20860 benoitc 20 0 55748 11m 1500 S 0.0 0.1 0:00.00 gunicorn: worker [test:app]
20861 benoitc 20 0 55748 11m 1500 S 0.0 0.1 0:00.01 gunicorn: worker [test:app]
At this point, two instances of gunicorn are running, handling the
incoming requests together. To phase the old instance out, you have to
send **WINCH** signal to the old master process, and its worker
processes will start to gracefully shut down.
t this point you can still revert to the old server because it hasn't closed its listen sockets yet, by following these steps:
- Send HUP signal to the old master process - it will start the worker processes without reloading a configuration file
- Send QUIT signal to the new master process to gracefully shut down its worker processes
- Send TERM signal to the new master process to force it quit
If for some reason new worker processes do not quit, send KILL signal to
them After new master process quits, the old master process removes
.oldbin suffix from its .pid file, and everything is exactly as before
the upgrade attempt.
If an update is successful and you want to keep the new server, send
QUIT signal to the old master process to leave only new server
running::
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
20854 benoitc 20 0 55748 12m 3348 S 0.0 0.2 0:00.45 gunicorn: master [test:app]
20859 benoitc 20 0 55748 11m 1500 S 0.0 0.1 0:00.02 gunicorn: worker [test:app]
20860 benoitc 20 0 55748 11m 1500 S 0.0 0.1 0:00.02 gunicorn: worker [test:app]
20861 benoitc 20 0 55748 11m 1500 S 0.0 0.1 0:00.01 gunicorn: worker [test:app]