159 lines
4.7 KiB
Plaintext
159 lines
4.7 KiB
Plaintext
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[[rolling-upgrades]]
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=== Rolling upgrades
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A rolling upgrade allows an Elasticsearch cluster to be upgraded one node at
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a time so upgrading does not interrupt service. Running multiple versions of
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Elasticsearch in the same cluster beyond the duration of an upgrade is
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not supported, as shards cannot be replicated from upgraded nodes to nodes
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running the older version.
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Rolling upgrades can be performed between minor versions. Elasticsearch
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6.x supports rolling upgrades from *Elasticsearch 5.6*.
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Upgrading from earlier 5.x versions requires a <<restart-upgrade,
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full cluster restart>>. You must <<reindex-upgrade,reindex to upgrade>> from
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versions prior to 5.x.
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To perform a rolling upgrade:
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. *Disable shard allocation*.
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+
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--
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include::disable-shard-alloc.asciidoc[]
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--
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. *Stop non-essential indexing and perform a synced flush.* (Optional)
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+
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--
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While you can continue indexing during the upgrade, shard recovery
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is much faster if you temporarily stop non-essential indexing and perform a
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<<indices-synced-flush, synced-flush>>.
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include::synced-flush.asciidoc[]
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--
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. [[upgrade-node]] *Shut down a single node*.
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+
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--
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include::shut-down-node.asciidoc[]
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--
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. *Upgrade the node you shut down.*
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+
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--
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include::upgrade-node.asciidoc[]
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include::set-paths-tip.asciidoc[]
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--
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. *Upgrade any plugins.*
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+
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Use the `elasticsearch-plugin` script to install the upgraded version of each
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installed Elasticsearch plugin. All plugins must be upgraded when you upgrade
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a node.
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. *Start the upgraded node.*
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+
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--
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Start the newly-upgraded node and confirm that it joins the cluster by checking
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the log file or by submitting a `_cat/nodes` request:
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[source,sh]
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--------------------------------------------------
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GET _cat/nodes
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--------------------------------------------------
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// CONSOLE
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--
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. *Reenable shard allocation.*
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+
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--
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Once the node has joined the cluster, reenable shard allocation to start using
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the node:
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[source,js]
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--------------------------------------------------
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PUT _cluster/settings
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{
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"transient": {
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"cluster.routing.allocation.enable": "all"
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}
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}
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--------------------------------------------------
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// CONSOLE
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--
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. *Wait for the node to recover.*
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+
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--
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Before upgrading the next node, wait for the cluster to finish shard allocation.
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You can check progress by submitting a <<cat-health,`_cat/health`>> request:
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[source,sh]
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--------------------------------------------------
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GET _cat/health
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--------------------------------------------------
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// CONSOLE
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Wait for the `status` column to switch from `yellow` to `green`. Once the
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node is `green`, all primary and replica shards have been allocated.
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[IMPORTANT]
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====================================================
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During a rolling upgrade, primary shards assigned to a node running the new
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version cannot have their replicas assigned to a node with the old
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version. The new version might have a different data format that is
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not understood by the old version.
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If it is not possible to assign the replica shards to another node
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(there is only one upgraded node in the cluster), the replica
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shards remain unassigned and status stays `yellow`.
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In this case, you can proceed once there are no initializing or relocating shards
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(check the `init` and `relo` columns).
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As soon as another node is upgraded, the replicas can be assigned and the
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status will change to `green`.
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====================================================
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Shards that were not <<indices-synced-flush,sync-flushed>> might take longer to
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recover. You can monitor the recovery status of individual shards by
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submitting a <<cat-recovery,`_cat/recovery`>> request:
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[source,sh]
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--------------------------------------------------
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GET _cat/recovery
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--------------------------------------------------
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// CONSOLE
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If you stopped indexing, it is safe to resume indexing as soon as
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recovery completes.
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--
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. *Repeat*
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+
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--
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When the node has recovered and the cluster is stable, repeat these steps
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for each node that needs to be updated.
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--
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[IMPORTANT]
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====================================================
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During a rolling upgrade, the cluster continues to operate normally. However,
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any new functionality is disabled or operates in a backward compatible mode
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until all nodes in the cluster are upgraded. New functionality
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becomes operational once the upgrade is complete and all nodes are running the
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new version. Once that has happened, there's no way to return to operating
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in a backward compatible mode. Nodes running the previous major version will
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not be allowed to join the fully-updated cluster.
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In the unlikely case of a network malfunction during the upgrade process that
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isolates all remaining old nodes from the cluster, you must take the
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old nodes offline and upgrade them to enable them to join the cluster.
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====================================================
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