43 lines
1.5 KiB
ReStructuredText
43 lines
1.5 KiB
ReStructuredText
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=================
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Install memcached
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=================
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[TODO: Verify that Oslo supports hash synchronization;
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if so, this should not take more than load balancing.]
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[TODO: This hands off to two different docs for install information.
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We should choose one or explain the specific purpose of each.]
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Most OpenStack services can use memcached
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to store ephemeral data such as tokens.
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Although memcached does not support
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typical forms of redundancy such as clustering,
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OpenStack services can use almost any number of instances
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by configuring multiple hostnames or IP addresses.
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The memcached client implements hashing
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to balance objects among the instances.
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Failure of an instance only impacts a percentage of the objects
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and the client automatically removes it from the list of instances.
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To install and configure memcached, read the
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`official documentation <https://code.google.com/p/memcached/wiki/NewStart>`_.
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Memory caching is managed by `oslo.cache
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<http://specs.openstack.org/openstack/oslo-specs/specs/kilo/oslo-cache-using-dogpile.html>`_
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so the way to use multiple memcached servers is the same for all projects.
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[TODO: Should this show three hosts?]
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Example configuration with two hosts:
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::
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memcached_servers = controller1:11211,controller2:11211
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By default, `controller1` handles the caching service but,
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if the host goes down, `controller2` does the job.
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For more information about memcached installation,
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see the `OpenStack Administrator Guide
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<http://docs.openstack.org/admin-guide/>`_.
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