A complete overview of upgrading Elasticsearch including common tips

Opster Team

Nov 2020

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The following configuration error was detected on node 123...

Description

This error can have a severe impact on your system. It's important to understand that it was caused by...

Recommendation

In order to resolve this issue and prevent it from occurring again, we recommend that you begin by changing the configuration to...

X-PUT curl -H "Content-Type: application/json" [customized recommendation]

Overview

Upgrade refers to migrating your Elasticsearch version to a newer version. An upgrade of an existing cluster can be done in two ways: through a rolling upgrade and through a full cluster restart. The benefit of a rolling upgrade is having zero downtime.

Common problems and important points

The major problem with upgrades is version incompatibility. Elasticsearch supports rolling upgrades only between minor versions. You need to make sure to go through the official documentation to see if your cluster can support a rolling upgrade, otherwise a complete reindexing is required.
Once you upgrade an Elasticsearch node, a rollback can not be done. You need to make sure to take data backups before an upgrade.
Elasticsearch continuously removes or deprecates some of its features with every release, so keep an eye on the change logs of each version before planning an upgrade.
While doing a rolling upgrade, it is important to disable shard allocation before stopping a node and enable the shard allocation when node is upgraded and restarted. This process helps in avoiding unnecessary IO load in the cluster.