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Merge "Document memcache max size with shard ranges"

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Zuul 2021-01-27 21:08:38 +00:00 committed by Gerrit Code Review
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doc/source/deployment_guide.rst
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@ -489,6 +489,29 @@ that have available RAM and CPU. Typically Memcached is run on the proxy
servers. The ``memcache_servers`` config option in the ``proxy-server.conf``
should contain all memcached servers.
*************************
Shard Range Listing Cache
*************************
When a container gets :ref:`sharded<sharding_doc>` the root container will still be the
primary entry point to many container requests, as it provides the list of shards.
To take load off the root container Swift by default caches the list of shards returned.
As the number of shards for a root container grows to more than 3k the memcache default max
size of 1MB can be reached. Care is needed to keep an eye on the current value or resize it
to something like 5MB.
Memcache has a ``stats sizes`` option that can point out the current size usage. As this
reaches the current max an increase might be in order::
# telnet <memcache server> 11211
> stats sizes
STAT 160 2
STAT 448 1
STAT 576 1
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