Comment 15 for bug 1538645

Reviewed: https://review.openstack.org/275820
Committed: https://git.openstack.org/cgit/openstack/fuel-agent/commit/?id=c726948f17c948a5307bbb7241f4b4e1f85f1d23
Submitter: Jenkins
Branch: master

commit c726948f17c948a5307bbb7241f4b4e1f85f1d23
Author: Alexander Gordeev <email address hidden>
Date: Wed Feb 3 19:17:29 2016 +0300

    Handle SIGTERM to shut down gracefully

    Apparently, fuel-agent doesn't handle any signal received except for SIGINT
    which is automatically converted by python to KeyboardInterrupt() exception.

    fuel-agent is unable to send signal for spawned processes, just because
    utils.execute doesn't know PIDs of opened subprocessess. To mitigate that flaw,
    fuel-agent will use process group to distribute signals.

    Process groups are used to control the distribution of signals.
    A signal directed to a process group is delivered individually to all of the
    processes that are members of the group.

    That allows fuel-agent to send signals to subprocesses without knowing thier
    exact PIDs.

    Change-Id: Ie59c0425f031fa94e517b79df0a0fc3d0c3e7a07
    Related-Bug: #1538645