<snip />
> It would also be very useful to be able to run arbitrary commands, not
> necessarily or strictly subprocess management, on program start and/or
> stop. A couple of things I'd like to use this for:
>
> - taking a load balancer back-end down before stopping and bringing it
> back up after starting a program
> - priming a backend with a few requests after starting and before
> bringing the back-end back up
>
> I've been trying to figure out what the right way to think about this
> should be. The program should not successfully stop without first
> taking down the back-end nor should a start be considered successful
> without successfully priming the program and then bringing the back-end
> back up. So what's the right place to do this? Is it even possible to
> achieve this with events or a wrapper script? Should this be something
> that supervisor core does? Is this outside the scope of supervisor?
Thought I might share the approach we've been using: we've altered our
wsgi server to take a sighup and subsequently do the following: finish
all open requests, stop taking new requests, display a change to the
status check for the load balancer that tells the load balancer to
remove the server from the pool, a longer timeout that does a hard
shutdown of the server after an interval.
We then use fabric to drive supervisorctl to do the actual recycling.
Supervisord is configure to send the HUP.
def cycle_super(app, deploydir=DEPLOYDIR):
"""
Cycle apps through supervisor
"""
with cd(path(deploydir) / 'supervisor'):
with hide('running', 'stdout', 'stderr'):
out = run('bin/python bin/supervisorctl avail')
procs = [x.split(' ', 1)[0] for x in out.split('\n')]
with hide('running'):
for proc in procs:
if proc.startswith(app):
run('bin/python bin/supervisorctl restart %s' %proc)
run('bin/python bin/supervisorctl status')
This works ok, but is time constrained by the number of processes
restarted. Being able to parallelize this a bit would be nice (say
cycle/4 and smartly cycle N process in N/4 groups).
That being said, just having a basic cycling command is more important
to me than say dependency managment or concurrent cycling.
-w
--
>>>
Whit Morriss
CodeMonkey
[email protected]
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