Comment 25 for bug 1311804

Reviewed: https://review.openstack.org/227589
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=81823e86328e62850a89aef9f0b609bfc0a6dacd
Submitter: Jenkins
Branch: master

commit 81823e86328e62850a89aef9f0b609bfc0a6dacd
Author: John Kasperski <email address hidden>
Date: Thu Sep 24 18:16:18 2015 -0500

    Improve performance of ensure_namespace

    The ensure_namespace method calls IpNetnsCommand.exists to
    determine if the specified namespace exists or not. This is
    accomplished by listing all namespaces with "ip netns list"
    and then looping through the output to determine if the specified
    namespace was included in the output.

    Research of various Linux operating systems has indicated that
    namespaces are represented as files in /var/run/netns and root
    authority is "typically" not required in order to look at the
    files in this subdirectory.

    The existing configuration option "use_helper_for_ns_read"
    will be used to determine if the root-helper should be used to
    to retrieve the list of namespaces. If this configuraton option
    is set to False, the native python os.listdir(/var/run/netns)
    will be used.

    Related-Bug: #1311804
    Closes-Bug: #1497396
    Change-Id: I9da627d07d6cbb6e5ef1a921a5f22963317a04e2