Comment 14 for bug 1247056

Reviewed: https://review.openstack.org/83041
Committed: https://git.openstack.org/cgit/openstack/python-novaclient/commit/?id=98934d7bf1464afe0f7fe98efd2a591d95ac9c41
Submitter: Jenkins
Branch: master

commit 98934d7bf1464afe0f7fe98efd2a591d95ac9c41
Author: Boris Pavlovic <email address hidden>
Date: Wed Mar 26 15:22:03 2014 +0400

    Fix session handling in novaclient

    Prior to this patch, novaclient was handling sessions in an inconsistent
    manner.

    Every time we created a client instance, it would use a global
    connection pool, which made it difficult to use in a process that is
    meant to be forked.

    Obviously sessions like the ones provided by the requests library that
    will automatically cause connections to be kept alive should not be
    implicit. This patch moves the novaclient back to the age of a single
    session-less request call by default, but also adds two more
    resource-reuse friendly options that a user needs to be explicit about.

    The first one is that both v1_1 and v3 clients can now be used as
    context managers,. where the session will be kept open (and thus the
    connection kept-alive) for the duration of the with block. This is far
    more ideal for a web worker use-case as the session can be made
    request-long.

    The second one is the per-instance session. This is very similar to what
    we had up until now, except it is not a global object so forking is
    possible as long as each child instantiates it's own client. The session
    once created will be kept open for the duration of the client object
    lifetime.

    Please note: client instances are not thread safe. As can be seen from
    above forking example - if you wish to use threading/multiprocessing,
    you *must not* share client instances.

    DocImpact

    Related-bug: #1247056
    Closes-Bug: #1297796
    Co-authored-by: Nikola Dipanov <email address hidden>
    Change-Id: Id59e48f61bb3f3c6223302355c849e1e99673410