Elasticsearch How to Upgrade Elasticsearch from Version 7 to Version 8

By Opster Expert Team

Updated: Jan 28, 2024

| 6 min read

Quick Links

• Upgrade Elasticsearch 7.17 to Elasticsearch 8.x
  • Preparing to upgrade Elasticsearch nodes
    1. Use the Kibana Upgrade Assistant
    2. Check the deprecation log
    3. Review the breaking changes
    4. Check the Elasticsearch plugins’ compatibility
    5. Set up a test environment
    6. Backup your data
    7. Check your security configuration
• The correct order for upgrading nodes
• How to upgrade nodes in a rolling upgrade
• Kibana deprecation issue

Upgrade Elasticsearch 7.17 to Elasticsearch 8.x

In this article, we will focus on upgrading Elasticsearch 7.17 to Elasticsearch 8.x. For more information on version upgrades in general, the different methods available, and everything you need to know prior to initiating the upgrade, you can see our complete guide here: How to Upgrade Elasticsearch Versions.  

Rolling upgrades are only supported from Elasticsearch version 7.17 to Elasticsearch version 8.x. To upgrade from earlier versions (7.1, 7.2, etc.) to version 8, you need a full cluster restart or you must upgrade first to version 7.17 before upgrading to version 8.

Preparing to upgrade Elasticsearch nodes

Elasticsearch nodes cannot be downgraded after upgrading. Before starting the upgrade process you should do the following: 

1. Use the Kibana Upgrade Assistant

The Kibana Upgrade Assistant is very helpful because it can indicate:

• Indices that are not compatible with version 8 and must be reindexed.
• Settings in elasticsearch.yml and/or kibana.yml that are deprecated and must be updated/replaced.
• Cluster settings that are not compatible with version 8.

2. Check the deprecation log 

You should read and resolve any issues highlighted in the deprecation log. These logs are usually located in:

/var/log/elasticsearch/Your-Cluster-Name_deprecation.log

3. Review the breaking changes

Breaking changes documentation is published with each new version of Elasticsearch to make you aware of any functionality that may change or disappear. You should always check that documentation to ensure that none of those settings, configurations, or mappings are being used in your setup. The main things that could be affected are:

• Node configuration (elasticsearch.yml)
• Index mappings and templates
• Cluster settings
• Code used in Elasticsearch clients (applications and indexing scripts)

The most important breaking changes in version 8 are:

• Doc_types are deprecated, and all references to them must be removed 
• Security is enabled by default
• Kibana can no longer use “elastic” user, it must have its own “kibana_system” user
• Python client syntax changes, e.g., instead of “body”, you need to pass in separate arguments for “query”, ”aggs”, ”sort”, etc.

4. Check the Elasticsearch plugins’ compatibility

If you are using any Elasticsearch plugins, you should check the availability and compatibility of those plugins with the new version.

In particular, bear in mind that most of the snapshot repository plugins are now part of the standard distribution, with no plugin required.

5. Set up a test environment 

You should first try the upgrade process in a test or staging environment in order to check and resolve all issues before upgrading your production cluster.

6. Backup your data  

Remember that it is not possible to downgrade an Elasticsearch node, so the only way to practically reverse a failed upgrade is to create a new cluster with the old version and recover your data from snapshots. Therefore, it is essential to take snapshots of all Elasticsearch indices before starting the upgrade process.

7. Check your security configuration

Security is enabled by default in version 8, so if you do NOT have security enabled in version 7, it is recommended to either set up security in version 7 before upgrading or set:

xpack.security.enabled: false

It is not recommended to try to add security and upgrade in the same process because adding tls certificates will result in some downtime.

Note that Kibana often requires some extra security configuration, which should be performed BEFORE upgrading. You can read more about this below.

After taking all the steps listed above, we are ready to upgrade Elasticsearch Cluster version 7.17.5 to Elasticsearch version 8.3.3.

The correct order for upgrading nodes

1. Begin by upgrading nodes that are not master-eligible. To find these nodes, use either the GET /_nodes/_all,master:false/_none API call or locate nodes configured with node.master: false.
2. Proceed with the upgrade tier-by-tier, starting with the frozen tier. Complete the upgrade for all nodes in each data tier before moving to the next one. Upgrade the frozen tier first, followed by the cold, warm, and finally the hot tier. This ensures that the data can still flow through the tiers during the upgrade. To obtain a list of nodes in a specific tier, use the GET /_nodes request. For example, GET /_nodes/data_frozen:true/_none.
3. Finally, upgrade the master-eligible nodes. Retrieve a list of these nodes using GET /_nodes/master:true.

Following this order guarantees that all nodes can join the cluster during the upgrade process. Upgraded nodes can join a cluster with an older master, but older nodes may not be able to join a cluster with an upgraded master.

Upgrading nodes in a rolling upgrade

To stop a node, run:

systemctl stop elasticsearch

To disable shard allocation, run:

PUT _cluster/settings
{
  "persistent": {
    "cluster.routing.allocation.enable": "primaries"
  }
}

To remove plugins, e.g., s3:

sudo bin/elasticsearch-plugin remove repository-s3

To reload the daemon after upgrading:

systemctl   daemon-reload
systemctl  enable elasticsearch

To re-enable shard allocation, run:

PUT _cluster/settings
{
  "persistent": {
    "cluster.routing.allocation.enable": null
  }
}

To get cluster status and see how many nodes are in the cluster, use:

GET _cluster/health

Kibana deprecation issue

When upgrading an Elasticsearch cluster, it is common to encounter the following error:

“Using ‘elasticsearch.username’ elastic is deprecated”

To solve that issue, run the following command BEFORE upgrading the Elasticsearch cluster:

POST /_security/service/elastic/kibana/credential/token

Doing so will create the following result:

{
  "created" : true,
  "token" : {
    "name" : "token_NHoHZYIB67fR10103kQc",
    "value" : "AAEAAWVsYXN0aWMva2liYW5hL3Rva2VuX05Ib0haWUlCNjdmUjEwMTAza1FjOkFtMnlQcjB1UmNDZWU3WUIxSVJDa1E"
  }
}

Then, you copy the value and add the configuration below to kibana.yml:

elasticsearch.serviceAccountToken:AAEAAWVsYXN0aWMva2liYW5hL3Rva2VuX05Ib0haWUlCNjdmUjEwMTAza1FjOkFtMnlQcjB1UmNDZWU3WUIxSVJDa1E"

And then remove these configurations lines from kibana.yml:

elasticsearch.username: "elastic"
elasticsearch.password: "password"

After that, you should restart Kibana and ensure that it can still connect and that the issue has been removed from the Kibana Upgrade Assistant.