openstack/swift
Code Issues Proposed changes

Document memcache max size with shard ranges

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When you start getting more then 3k shards in a root container the
cached shard range listing can get bigger then the default max size for
memcache (1MB).

So add a mention about it in the configuration guide.

Fixes bug 1890643

Change-Id: If380410c17ed9ebc014b8198af0ea8d502deacc8
This commit is contained in:
Matthew Oliver 2021-01-07 17:06:55 +11:00
parent 077ba77ea6
commit 8df3d1505a
1 changed files with 23 additions and 0 deletions
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doc/source/deployment_guide.rst
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@ -492,6 +492,29 @@ on any servers that have available RAM and CPU. At Rackspace, we run
Memcached 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
END
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System Time
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