172 lines
5.9 KiB
Plaintext
172 lines
5.9 KiB
Plaintext
[[rolling-upgrades]]
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=== Rolling upgrades
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A rolling upgrade allows the Elasticsearch cluster to be upgraded one node at
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a time, with no downtime for end users. Running multiple versions of
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Elasticsearch in the same cluster for any length of time beyond that required
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for an upgrade is not supported, as shards will not be replicated from the
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more recent version to the older version.
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Consult this <<setup-upgrade,table>> to verify that rolling upgrades are
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supported for your version of Elasticsearch.
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To perform a rolling upgrade:
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==== Step 1: Disable shard allocation
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When you shut down a node, the allocation process will immediately try to
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replicate the shards that were on that node to other nodes in the cluster,
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causing a lot of wasted I/O. This can be avoided by disabling allocation
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before shutting down a node:
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[source,json]
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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": "none"
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}
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}
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--------------------------------------------------
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// AUTOSENSE
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==== Step 2: Stop non-essential indexing and perform a synced flush (Optional)
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added[1.6.0,Synced flush is only supported in Elasticsearch 1.6.0 and above]
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You may happily continue indexing during the upgrade. However, shard recovery
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will be much faster if you temporarily stop non-essential indexing and issue a
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<<indices-synced-flush, synced-flush>> request:
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[source,json]
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--------------------------------------------------
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POST /_flush/synced
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--------------------------------------------------
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// AUTOSENSE
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A synced flush request is a ``best effort'' operation. It will fail if there
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are any pending indexing operations, but it is safe to reissue the request
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multiple times if necessary.
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[[upgrade-node]]
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==== Step 3: Stop and upgrade a single node
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Shut down one of the nodes in the cluster *before* starting the upgrade.
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[TIP]
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================================================
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When using the zip or tarball packages, the `config`, `data`, `logs` and
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`plugins` directories are placed within the Elasticsearch home directory by
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default.
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It is a good idea to place these directories in a different location so that
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there is no chance of deleting them when upgrading Elasticsearch. These
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custom paths can be <<paths,configured>> with the `path.config` and
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`path.data` settings.
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The Debian and RPM packages place these directories in the
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<<setup-dir-layout,appropriate place>> for each operating system.
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================================================
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To upgrade using a <<setup-repositories,Debian or RPM>> package:
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* Use `rpm` or `dpkg` to install the new package. All files should be
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placed in their proper locations, and config files should not be
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overwritten.
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To upgrade using a zip or compressed tarball:
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* Extract the zip or tarball to a new directory, to be sure that you don't
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overwrite the `config` or `data` directories.
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* Either copy the files in the `config` directory from your old installation
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to your new installation, or use the `--path.config` option on the command
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line to point to an external config directory.
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* Either copy the files in the `data` directory from your old installation
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to your new installation, or configure the location of the data directory
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in the `config/elasticsearch.yml` file, with the `path.data` setting.
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==== Step 4: Start the upgraded node
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Start the now upgraded node and confirm that it joins the cluster by checking
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the log file or by checking the output of this 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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// AUTOSENSE
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==== Step 5: Reenable shard allocation
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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,json]
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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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// AUTOSENSE
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==== Step 6: Wait for the node to recover
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You should wait for the cluster to finish shard allocation before upgrading
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the next node. You can check on progress with the <<cat-health,`_cat/health`>>
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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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// AUTOSENSE
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Wait for the `status` column to move from `yellow` to `green`. Status `green`
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means that 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 with the higher
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version will never have their replicas assigned to a node with the lower
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version, because the newer version may have a different data format which is
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not understood by the older version.
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If it is not possible to assign the replica shards to another node with the
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higher version -- e.g. if there is only one node with the higher version in
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the cluster -- then the replica shards will remain unassigned and the
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cluster health will remain status `yellow`.
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In this case, check that there are no initializing or relocating shards (the
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`init` and `relo` columns) before proceding.
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As soon as another node is upgraded, the replicas should be assigned and the
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cluster health will reach status `green`.
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====================================================
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Shards that have not been <<indices-synced-flush,sync-flushed>> may take some time to
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recover. The recovery status of individual shards can be monitored with the
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<<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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// AUTOSENSE
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If you stopped indexing, then it is safe to resume indexing as soon as
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recovery has completed.
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==== Step 7: Repeat
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When the cluster is stable and the node has recovered, repeat the above steps
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for all remaining nodes.
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