[[rolling-upgrades]] == Rolling upgrades A rolling upgrade allows an {es} cluster to be upgraded one node at a time so upgrading does not interrupt service. Running multiple versions of {es} in the same cluster beyond the duration of an upgrade is not supported, as shards cannot be replicated from upgraded nodes to nodes running the older version. Rolling upgrades are supported: * Between minor versions * https://www.elastic.co/guide/en/elastic-stack/6.8/upgrading-elastic-stack.html[From 5.6 to 6.8] * From 6.8 to {version} Upgrading directly to {version} from 6.7 or earlier requires a <>. To perform a rolling upgrade from 6.8 to {version}: . *Disable shard allocation*. + -- include::disable-shard-alloc.asciidoc[] -- . *Stop non-essential indexing and perform a synced flush.* (Optional) + -- While you can continue indexing during the upgrade, shard recovery is much faster if you temporarily stop non-essential indexing and perform a <>. include::synced-flush.asciidoc[] -- . *Temporarily stop the tasks associated with active {ml} jobs and {dfeeds}.* (Optional) + -- include::close-ml.asciidoc[] -- . [[upgrade-node]] *Shut down a single node*. + -- include::shut-down-node.asciidoc[] -- . *Upgrade the node you shut down.* + -- include::upgrade-node.asciidoc[] include::set-paths-tip.asciidoc[] -- . *Upgrade any plugins.* + Use the `elasticsearch-plugin` script to install the upgraded version of each installed {es} plugin. All plugins must be upgraded when you upgrade a node. . If you use {es} {security-features} to define realms, verify that your realm settings are up-to-date. The format of realm settings changed in version 7.0, in particular, the placement of the realm type changed. See <>. . *Start the upgraded node.* + -- Start the newly-upgraded node and confirm that it joins the cluster by checking the log file or by submitting a `_cat/nodes` request: [source,sh] -------------------------------------------------- GET _cat/nodes -------------------------------------------------- // CONSOLE -- . *Reenable shard allocation.* + -- Once the node has joined the cluster, remove the `cluster.routing.allocation.enable` setting to enable shard allocation and start using the node: [source,js] -------------------------------------------------- PUT _cluster/settings { "persistent": { "cluster.routing.allocation.enable": null } } -------------------------------------------------- // CONSOLE -- . *Wait for the node to recover.* + -- Before upgrading the next node, wait for the cluster to finish shard allocation. You can check progress by submitting a <> request: [source,sh] -------------------------------------------------- GET _cat/health?v -------------------------------------------------- // CONSOLE Wait for the `status` column to switch from `yellow` to `green`. Once the node is `green`, all primary and replica shards have been allocated. [IMPORTANT] ==================================================== During a rolling upgrade, primary shards assigned to a node running the new version cannot have their replicas assigned to a node with the old version. The new version might have a different data format that is not understood by the old version. If it is not possible to assign the replica shards to another node (there is only one upgraded node in the cluster), the replica shards remain unassigned and status stays `yellow`. In this case, you can proceed once there are no initializing or relocating shards (check the `init` and `relo` columns). As soon as another node is upgraded, the replicas can be assigned and the status will change to `green`. ==================================================== Shards that were not <> might take longer to recover. You can monitor the recovery status of individual shards by submitting a <> request: [source,sh] -------------------------------------------------- GET _cat/recovery -------------------------------------------------- // CONSOLE If you stopped indexing, it is safe to resume indexing as soon as recovery completes. -- . *Repeat* + -- When the node has recovered and the cluster is stable, repeat these steps for each node that needs to be updated. -- . *Restart machine learning jobs.* + -- include::open-ml.asciidoc[] -- [IMPORTANT] ==================================================== During a rolling upgrade, the cluster continues to operate normally. However, any new functionality is disabled or operates in a backward compatible mode until all nodes in the cluster are upgraded. New functionality becomes operational once the upgrade is complete and all nodes are running the new version. Once that has happened, there's no way to return to operating in a backward compatible mode. Nodes running the previous major version will not be allowed to join the fully-updated cluster. In the unlikely case of a network malfunction during the upgrade process that isolates all remaining old nodes from the cluster, you must take the old nodes offline and upgrade them to enable them to join the cluster. If you stop half or more of the master-eligible nodes all at once during the upgrade then the cluster will become unavailable, meaning that the upgrade is no longer a _rolling_ upgrade. If this happens, you should upgrade and restart all of the stopped master-eligible nodes to allow the cluster to form again, as if performing a <>. It may also be necessary to upgrade all of the remaining old nodes before they can join the cluster after it re-forms. ====================================================