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[OpenStack Infra <1883554@xxxxxxxxxxxxxxxxxx>]

Reviewed:  https://review.opendev.org/735618
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=e09d4d6dd0f6570400d28531e56d2166141357cb
Submitter: Zuul
Branch:    master

commit e09d4d6dd0f6570400d28531e56d2166141357cb
Author: Daniel Alvarez <dalvarez@xxxxxxxxxx>
Date:   Mon Jun 15 17:17:53 2020 +0200

    [OVN] Avoid unnecessary DB writes during agent liveness check
    
    As stated in the bug description, there are many writes of the
    agent liveness external_ids into the Chassis table. There was a
    protection to avoid bumping nb_cfg too frequently.
    
    The same protection is reused to avoid writing into the Chassis
    external_ids.
    
    This patch reduces the number of transactions to the SB database
    and, therefore, the recomputations that it causes to ovn-controller
    in all nodes.
    
    Change-Id: I5db90fde8e7394772ec23c6384c711096c246621
    Closes-Bug: #1883554
    Signed-off-by: Daniel Alvarez <dalvarez@xxxxxxxxxx>


** Changed in: neutron
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1883554

Title:
  [ovn] Agent liveness checks create too many writes into OVN db

Status in neutron:
  Fix Released

Bug description:
  Every time the agent liveness check is triggered (via API or periodically every agent_down_time / 2 seconds), there are a lot of writes into the SB database on the Chassis table.
  These writes triggers recomputation on ovn-controller running in all nodes having a considerable performance hit, especially under stress.

  
  After this commit was merged [0] we avoided bumping nb_cfg too frequently but still we're performing writes into the Chassis table to often, from all the workers.

  We should use the same logic in [1] to avoid writes that have happened
  recently.

  
  [0] https://opendev.org/openstack/neutron/commit/647b7f63f9dafedfa9fb6e09e3d92d66fb512f0b
  [1] https://github.com/openstack/neutron/blob/4de18104ae88a835544cefbf30c878aa49efc31f/neutron/plugins/ml2/drivers/ovn/mech_driver/mech_driver.py#L1075

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