Comment 31 for bug 1453350

Reviewed: https://review.openstack.org/181674
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=b672c26cb42ad3d9a17ed049b506b5622601e891
Submitter: Jenkins
Branch: master

commit b672c26cb42ad3d9a17ed049b506b5622601e891
Author: Kevin Benton <email address hidden>
Date: Fri Apr 15 06:05:56 2016 -0700

    Add provisioning blocks to status ACTIVE transition

    Sometimes an object requires multiple disjoint actors to complete
    a set of tasks before the status of the object should be transitioned
    to ACTIVE. The main example of this is when a port is being created.
    The L2 agent has to do its business to wire up the VIF, but at the same
    time the DHCP agent has to setup the DHCP reservation. This led to
    Nova booting the VM when the L2 agent was done even though the DHCP
    agent may have been nowhere near ready.

    This patch introduces a provisioning blocks mechansim that allows the
    entities to be tracked that need to be involved to make a transition
    to ACTIVE happen. See the devref in the dependent patch for a high-level
    view of how this works.

    The ML2 code is updated to use this new mechanism to prevent updating
    the port status to ACTIVE without both the DHCP agent and L2 agent
    reporting that the port is ready.

    The DHCP RPC API required a version bump to allow the port ready
    notification.

    This also adds a devref doc for the provisioning_blocks
    module with a high-level overview of how it works in addition
    to a detailed description of how it is used specifically with
    ML2, the L2 agents, and the DHCP agents.

    Closes-Bug: #1453350
    Change-Id: Id85ff6de1a14a550ab50baf4f79d3130af3680c8