[Bug 1521958] Re: rabbit: starvation of connections for reply

[Xiang Hui]

Hello Corey,

  Thanks for pointing out that and do all the review, I have assigned
this bug to you for your lots of efforts on liberty/kilo/juno/icehouse,
the liberty/kilo patches may just cherry-pick from the upstream as I
remember, feel free to change the juno/icehouse patches if they need
improvements, thanks a lot : )

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https://bugs.launchpad.net/bugs/1521958

Title:
  rabbit: starvation of connections for reply

Status in Ubuntu Cloud Archive:
  New
Status in Ubuntu Cloud Archive juno series:
  New
Status in oslo.messaging:
  Fix Released
Status in oslo.messaging package in Ubuntu:
  New
Status in oslo.messaging source package in Trusty:
  New
Status in oslo.messaging source package in Vivid:
  Fix Released

Bug description:
  Hi,

  When a client died/restart/stop but was waiting more replies that the rpc_connection_pool size,
  the server will hold all connections from the pool during the retry logic in case of the client come back with the same reply_queue_id (that occurs only is rabbit is restart, not the client).

  Cheers,

  
  ---------------------------

  [Impact]

  This patch addresses an issue when multiple clients lost
  networks/died/restart/stop, the server will hold all connections from
  the pool(rpc_connection_pool size) during the retry logic in case of
  the client come back with the same reply_queue_id (that occurs only is
  rabbit is restart, not the client), and which cause nova-conductor
  infinitely reconnects to rabbit if large nova-compute hosts are
  deployment until all of the connections of the old reply messages are
  expired, for the quite large scaled cloud, high availability is
  broken.

  [Test Case]

  Note steps are for trusty-icehouse, including latest oslo.messaging
  library (1.3.0-0ubuntu1.2 at the time of this writing).

  Deploy an OpenStack cloud w/ multiple rabbit nodes and multiple nova
  compute hosts then cut off the network between OpenStack services and
  RabbitMQ. Observe that the nova-conductor is infinitely reconnecting
  to rabbit nodes.

  [Regression Potential]

  None.

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