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75 lines
3.0 KiB
ReStructuredText
.. _highavailability:
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==================================
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High Availability Features in Salt
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==================================
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Salt supports several features for high availability and fault tolerance.
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Brief documentation for these features is listed alongside their configuration
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parameters in :ref:`Configuration file examples <configuration/examples>`.
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Multimaster
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===========
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Salt minions can connect to multiple masters at one time by configuring the
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`master` configuration parameter as a YAML list of all the available masters. By
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default, all masters are "hot", meaning that any master can direct commands to
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the Salt infrastructure.
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In a multimaster configuration, each master must have the same cryptographic
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keys, and minion keys must be accepted on all masters separately. The contents
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of file_roots and pillar_roots need to be kept in sync with processes external
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to Salt as well
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A tutorial on setting up multimaster with "hot" masters is here:
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:doc:`Multimaster Tutorial </topics/tutorials/multimaster>`
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Multimaster with Failover
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=========================
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Changing the ``master_type`` parameter from ``str`` to ``failover`` will
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cause minions to connect to the first responding master in the list of masters.
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Every ``master_alive_check`` seconds the minions will check to make sure
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the current master is still responding. If the master does not respond,
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the minion will attempt to connect to the next master in the list. If the
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minion runs out of masters, the list will be recycled in case dead masters
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have been restored. Note that ``master_alive_check`` must be present in the
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minion configuration, or else the recurring job to check master status
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will not get scheduled.
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Failover can be combined with PKI-style encrypted keys, but PKI is NOT
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REQUIRED to use failover.
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Multimaster with PKI and Failover is discussed in
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:doc:`this tutorial </topics/tutorials/multimaster_pki>`
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``master_type: failover`` can be combined with ``master_shuffle: True``
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to spread minion connections across all masters (one master per
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minion, not each minion connecting to all masters). Adding Salt Syndics
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into the mix makes it possible to create a load-balanced Salt infrastructure.
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If a master fails, minions will notice and select another master from the
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available list.
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Syndic
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======
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Salt's Syndic feature is a way to create differing infrastructure
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topologies. It is not strictly an HA feature, but can be treated as such.
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With the syndic, a Salt infrastructure can be partitioned in such a way that
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certain masters control certain segments of the infrastructure, and "Master
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of Masters" nodes can control multiple segments underneath them.
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Syndics are covered in depth in :doc:`Salt Syndic </topics/topology/syndic>`.
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Syndic with Multimaster
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=======================
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.. versionadded:: 2015.5.0
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Syndic with Multimaster lets you connect a syndic to multiple masters to provide
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an additional layer of redundancy in a syndic configuration.
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Syndics are covered in depth in :doc:`Salt Syndic </topics/topology/syndic>`.
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