The run loop has to change slightly to support graceful shutdown.
There is no way to interrupt a call to `futures.wait` so instead
the pattern, used by the async workers, is to sleep for only one
second at the most. The poll is extended to a one second timeout
to match.
Since threads are preemptively scheduled, it's possible that the
listener is closed when the request is actually handled. For this
reason it is necessary to slightly refactor the TConn class to store
the listening socket name. The name is checked once at the start of
the worker run loop.
Ref #922
Close all the listeners when the arbiter shuts down. By doing so,
workers can close the socket at the beginning of a graceful shut
down thereby informing the operating system that the socket can
be cleaned up. With this change, graceful exits with such workers
will refuse new connections while draining, allowing load balancers
to respond more quickly and avoiding leaving connections dangling
in the listen backlog, unaccepted.
Ref #922
By having a `getattr` implementation that proxies to the `sock`
attribute, there is a risk of infinite recursion when the socket
attribute is absent. After closing the socket and destroying it,
the recursion can be prevented by setting the attribute to `None`.
Since the changes from #1126, errors are not raised into the main
loop during a non-graceful shutdown. Therefore, these exception
clauses shouldn't be needed anymore.
Just like in the gevent worker, a blocking call should only be executed
from within a coroutine. The AssertionError around the main loop of the
eventlet worker can be removed, since it was there to catch
the exception raised by the sleep.
Currently if you configure statsd_host, a configured logger_class will never be used.
I think this makes a user configured logger class always take priority.
(This is PoC change, I will come back and add tests/docs if it's worth pursuing)
Manually including the traceback in the log msg causes some issues when
interacting with log formats, and in one case was causing the traceback
to be printed twice.
