Comment 6 for bug 1526277

Reviewed: https://review.openstack.org/264720
Committed: https://git.openstack.org/cgit/openstack/ironic/commit/?id=3429e3824c060071e59a117c19c95659c78e4c8b
Submitter: Jenkins
Branch: master

commit 3429e3824c060071e59a117c19c95659c78e4c8b
Author: Dmitry Tantsur <email address hidden>
Date: Thu Jan 7 12:12:59 2016 +0100

    Switch to Futurist library for asynchronous execution and periodic tasks

    This change switches the conductor to using Futurist library executor and
    periodic tasks worker instead of oslo.service periodic tasks. This allows
    running periodic tasks in parallel and relying on more standard interfaces
    (futures, executors) when dealing with asynchronous execution.

    A green thread executor is used instead of using an eventlet green pool
    directly. The maximum number of workers is taken from the existing
    workers_pool_size configuration option, and no tasks are allowed
    to be enqueued to mimic the previous behaviour (might be lifted later).

    The periodic tasks worker is using the same executor, and its main loop thread
    is also running on it. For this reason minimum value for workers_pool_size
    is now 3: periodic task main loop, keep alive thread and at least one thread for
    other tasks. A special decorator for driver-periodic tasks is now deprecated,
    as the generic decorator can be used there as well.

    Closes-Bug: #1526277
    Change-Id: I57bf7cebfb6db805b6c521bacfef2993b16ce1ee