In general, signals need only be sent to the master process. However, the signals Rainbows! uses internally to communicate with the worker processes are documented here as well. With the exception of TTIN/TTOU, signal handling matches the behavior of and nginx so it should be possible to easily share process management scripts between Rainbows!, unicorn and nginx.
HUP - reload config file, app, and gracefully restart all workers If the
"preload_app" directive is false (the default), then workers will also pick
up any application code changes when restarted. If "preload_app" is true,
then application code changes will have no effect; USR2 + QUIT (see below)
must be used to load newer code in this case. When reloading the
Gem.refresh will be called so updated code for
your application can pick up newly installed RubyGems. It is not
recommended that you uninstall libraries your application depends on while
Rainbows! is running, as respawned workers may
enter a spawn loop when they fail to load an uninstalled dependency.
INT/TERM - quick shutdown, kills all workers immediately
QUIT - graceful shutdown, waits for workers to finish their current request before finishing. Since Rainbows 5.1.0 (Jan 2017), this waits requests deferred to a separate thread with EventMachine (app.deferred?(env) => true).
USR1 - reopen all logs owned by the master and all workers See Unicorn::Util.reopen_logs for what is considered a log.
USR2 - reexecute the running binary. A separate QUIT should be sent to the original process once the child is verified to be up and running.
WINCH - gracefully stops workers but keep the master running. This will only work for daemonized processes.
TTIN - increment the number of worker processes by one
TTOU - decrement the number of worker processes by one
Sending signals directly to the worker processes should not normally be needed. If the master process is running, any exited worker will be automatically respawned.
INT/TERM - Quick shutdown, immediately exit. Unless WINCH has been sent to the master (or the master is killed), the master process will respawn a worker to replace this one.
QUIT - Gracefully exit after finishing the current request. Unless WINCH has been sent to the master (or the master is killed), the master process will respawn a worker to replace this one. This currently does not wait for requests deferred to a separate thread when using EventMachine (when app.deferred?(env) => true)
USR1 - Reopen all logs owned by the worker process. See Unicorn::Util.reopen_logs for what is considered a log. Unlike unicorn, log files are reopened immediately in Rainbows! since worker processes are likely to be serving multiple clients simutaneously, we can't wait for all of them to finish.
You may replace a running instance of rainbows with a new one without losing any incoming connections. Doing so will reload all of your application code, unicorn/Rainbows! config, Ruby executable, and all libraries. The only things that will not change (due to OS limitations) are:
The path to the rainbows executable script. If you want to change to a different installation of Ruby, you can modify the shebang line to point to your alternative interpreter.
The procedure is exactly like that of nginx:
Send USR2 to the master process
Check your process manager or pid files to see if a new master spawned successfully. If you're using a pid file, the old process will have ".oldbin" appended to its path. You should have two master instances of rainbows running now, both of which will have workers servicing requests. Your process tree should look something like this:
rainbows master (old) \_ rainbows worker \_ rainbows worker \_ rainbows worker \_ rainbows worker \_ rainbows master \_ rainbows worker \_ rainbows worker \_ rainbows worker \_ rainbows worker
You can now send WINCH to the old master process so only the new workers serve requests. If your rainbows process is bound to an interactive terminal, you can skip this step. Step 5 will be more difficult but you can also skip it if your process is not daemonized.
You should now ensure that everything is running correctly with the new workers as the old workers die off.
If everything seems ok, then send QUIT to the old master. You're done!
If something is broken, then send HUP to the old master to reload the config and restart its workers. Then send QUIT to the new master process.
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