openstack/swift
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Merge "Update Memcached Considerations docs"

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Zuul 2021-01-29 01:20:21 +00:00 committed by Gerrit Code Review
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doc/source/deployment_guide.rst
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@ -498,8 +498,17 @@ primary entry point to many container requests, as it provides the list of shard
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.
size of 1MB can be reached.
If you over-run your max configured memcache size you'll see messages like::
Error setting value in memcached: 127.0.0.1:11211: SERVER_ERROR object too large for cache
When you see these messages your root containers are getting hammered and
probably returning 503 reponses to clients. Override the default 1MB limit to
5MB with something like::
/usr/bin/memcached -I 5000000 ...
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::