Comment 20 for bug 1332058

Reviewed: https://review.openstack.org/119452
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=0010803288748fcd3ce7dba212a54bffe7a61a0c
Submitter: Jenkins
Branch: master

commit 0010803288748fcd3ce7dba212a54bffe7a61a0c
Author: Yuriy Taraday <email address hidden>
Date: Thu Aug 28 14:27:58 2014 +0400

    Add a pool of memcached clients

    This patchset adds a pool of memcache clients. This pool allows for reuse of
    a client object, prevents too many client object from being instantiated, and
    maintains proper tracking of dead servers so as to limit delays
    when a server (or all servers) become unavailable.

    The new memcache pool backend is available either by being set as the memcache
    backend or by using keystone.token.persistence.backends.memcache_pool.Token for
    the Token memcache persistence driver.

    [memcache]
    servers = 127.0.0.1:11211
    dead_retry = 300
    socket_timeout = 3
    pool_maxsize = 10
    pool_unused_timeout = 60

    Where:
    - servers - comma-separated list of host:port pairs (was already there);
    - dead_retry - number of seconds memcached server is considered dead
      before it is tried again;
    - socket_timeout - timeout in seconds for every call to a server;
    - pool_maxsize - max total number of open connections in the pool;
    - pool_unused_timeout - number of seconds a connection is held unused in
      the pool before it is closed;

    The new memcache pool backend can be used as the driver for the Keystone
    caching layer. To use it as caching driver, set
    'keystone.cache.memcache_pool' as the value of the [cache]\backend option,
    the other options are the same as above, but with 'memcache_' prefix:

    [cache]
    backend = keystone.cache.memcache_pool
    memcache_servers = 127.0.0.1:11211
    memcache_dead_retry = 300
    memcache_socket_timeout = 3
    memcache_pool_maxsize = 10
    memcache_pool_unused_timeout = 60

    Co-Authored-By: Morgan Fainberg <email address hidden>
    Closes-bug: #1332058
    Closes-bug: #1360446
    Change-Id: I3544894482b30a47fcd4fac8948d03136fd83f14