Comment 4 for bug 1882927

Reviewed: https://review.opendev.org/728779
Committed: https://git.openstack.org/cgit/openstack/puppet-tripleo/commit/?id=c04057b58b3a13a433f28d229a8f0908df253b57
Submitter: Zuul
Branch: master

commit c04057b58b3a13a433f28d229a8f0908df253b57
Author: Bogdan Dobrelya <email address hidden>
Date: Mon May 18 10:14:21 2020 +0200

    Tune haproxy for long running sessions to use leastconn

    For long running sessions, the leastconn LB is more prefered than the
    default roundrobin. For long connections, it picks the least recently
    used of the servers with the lowest connection count.

    LRU LB strategy that leastconn uses also indirectly reduces the
    possibility of cascaded failures by smoothing out the high traffic
    spikes, which otherwise may be caused by unequal round-robin
    distribution of client connections upon executing it a fail-over to
    another backend.

    Heat API/cfn provides Orchestration API with a notion of long running
    tasks. Neutron server may maintain long running RPC calls to its
    agents. Cinder BlockStorage API provides long running volume and
    backup actions. Swift Proxy's PutObject etc. and Ceph RGW APIs, like
    https://docs.ceph.com/docs/master/radosgw/s3/bucketops/, have a notion
    of "long running" as well. Ironic Inspector API provides long running
    operations, like introspection of BM nodes. All those should benefit
    from the leastconn LB switch controlled by the new parameter.

    Closes-Bug: #1882927
    Change-Id: I9515af738113a3f7aa2ea07315889d4a6595d4eb
    Signed-off-by: Bogdan Dobrelya <email address hidden>