Open Stack

Hi, I'd like you to take a look at this patch for potential
documentation impact.
https://review.openstack.org/10903

Log:
commit ceddcb2616d7ac695da229fe6e99f7b61bd12211
Author: Yun Mao <yunmao at gmail.com>
Date:   Mon Aug 6 12:37:12 2012 -0400

    Add pluggable ServiceGroup monitoring APIs
    
    Summary:
    * provide a pluggable ServiceGroup monitoring API
    * refactor the old DB-based implementation to the new API
    
    Currently nova compute nodes periodically write to the database (every
    10 seconds by default) to report their liveness.  This implementation
    factors out this functionality and make it a set of abstract internal
    APIs with a pluggable backend implementation.  Currently it's named as
    ServiceGroup APIs.
    
    With this effort, we are hopeful to see the following benefits:
    
     * We expect to see more backend implementations in addition to the
    default database-based one, such as ZooKeeper (as described in
    blueprint zk-service-heartbeat) or rabbitmq heartbeat based.
    
     * We expect the code to live in openstack-common so projects other
    than Nova can take advantage of the internal APIs.
    
     * Lay the foundations to use lower overhead heartbeat mechanisms
    which scale better.
    
     * Other than reporting whether a node in a service group is up or
    down, the code may also be used to query for members.  Other parts of
    the code could also take advantage of the new APIs. One noteable
    example is the MatchMaker in the rpc library, which may even become
    redundant. We have been working with Eric at Cloudscaling to see how
    this fits with the matchmaker. It is likely that this code will need
    to be used, at least by the peer-to-peer based RPC mechanisms, to
    implement the new create_worker method.
    
    DocImpact
    
    Co-authored-by: Pavel Kravchenco <kpavel at il.ibm.com>
    Co-authored-by: Alexey Roytman <roytman at il.ibm.com>
    
    Change-Id: I51645687249c75e7776a684f19529a1e78f33a41