Comment 1 for bug 1959562

Reviewed: https://review.opendev.org/c/openstack/oslo.cache/+/826569
Committed: https://opendev.org/openstack/oslo.cache/commit/2ad2d52f4ecb63d9edfe3ae64cd9b7dece5330a0
Submitter: "Zuul (22348)"
Branch: stable/xena

commit 2ad2d52f4ecb63d9edfe3ae64cd9b7dece5330a0
Author: Hervé Beraud <email address hidden>
Date: Fri Aug 6 11:49:17 2021 +0200

    Add socket keepalive options to oslo.cache

    This patch specifies a set of options required to setup the
    socket keepalive of the dogpile.cache's pymemcache
    backend [1][2]. This setup from those options can later on
    be passed to this backend.

    This patch also sets up the socket keepalive object based on
    the configuration options passed via oslo.config and adds it
    as an argument to be passed to the selected oslo.cache backend.

    Dogpile.cache will be used as an interface between oslo.cache and
    pymemcache [3].

    This patch is needed to fix a TLS issue on stable branches introduced by
    pymemcache (since train), where if a cluster node disappear the client
    will fail without retrying to reconnect or to switch to an other node of
    the cluster.

    [1] https://github.com/sqlalchemy/dogpile.cache/pull/205
    [2]
    https://github.com/pinterest/pymemcache/commit/b289c87bb89b3ab477bd5d92c8951ab42c923923
    [3]
    https://dogpilecache.sqlalchemy.org/en/latest/api.html?highlight=keepalive#dogpile.cache.backends.memcached.PyMemcacheBackend.params.socket_keepalive

    Partial-Bug: #1959562
    Change-Id: I501100e1a48cdd4e094c08046e2150405dcf371e
    (cherry picked from commit f4fa6aa6fa2aca23a8f4f9e63c5a57dbcd2d1166)