[PATCH 1 of 2 STABLE] worker: be silent if killed by the main process

[Jun Wu]

Excerpts from Yuya Nishihara's message of 2017-04-23 00:55:45 +0900:
> On Fri, 21 Apr 2017 21:31:05 -0700, Jun Wu wrote:
> > Excerpts from Yuya Nishihara's message of 2017-04-22 12:18:52 +0900:
> > > > The new plan is to use SIGUSR2 to "kill" workers, SIGUSR2 handler is to do
> > > > sys.exit. So "killed!" is removed and traceback is kept.
> > > 
> > > What's the key difference from just making SIGTERM handler silent?
> > 
> > No "killed!" is printed. And users killing them manually will still get
> > "killed!".
> 
> I think that is the same sort of problem as SIGINT, which is no
> "interrupted!" is printed right now but we can't make worker processes
> print it. I guess both SIGINT and SIGTERM issues can be solved in the same
> way.

I finally get it. tl;dr I prefer moving SignalInterrupt to dispatch.py and
will do that.

The two approaches only differ in the case where a manual SIGTERM hits a
worker, the SIGUSR2 way will print "killed!" as it was before. But I think
not printing "killed!" in all cases is cleaner.

> That said, there should be no problem using SIGUSR2 for more explicit
> control of worker processes.