Configuring a multiple data center OpenSearch cluster

When the nodes in the OpenSearch cluster are hosted in different data centers, racks, or zones, you should use allocation awareness. This will ensure that the data is correctly spread between the different locations and that you will still have all your data in case the connection to a location is lost.

There are two kinds of allocation awareness: shard allocation awareness and forced awareness. The difference between these two is the way they handle the shards when a location is suddenly unreachable. Shard allocation awareness will assign the shards of the missing replicas nodes that can still be reached in the other locations. This can cause a big load on those nodes. If your nodes would not be able to handle this, you can solve this by using forced awareness instead. Forced awareness will never allow copies of the same shard to be allocated to the same locations.

Important

We recommend using shard allocation awareness, as we have not yet tested setups with forced awareness.

Tip

For more information , refer to Allocation Awareness in the OpenSearch documentation.

Configuring allocation awareness

To configure allocation awareness, you will need to add some parameters in the opensearch.yaml file on each node. To do so:

Stop the OpenSearch service on the Linux server.

For Debian-based systems, you can do this with following command:
```
sudo systemctl stop opensearch.service
```
Open the opensearch.yaml file. By default this is located in the /etc/opensearch/ folder.
Adjust the configuration as necessary.

For example, below you can see what the configuration would look like in a 6-node cluster spread over 2 data centers:
- Node 1, 2, and 3 in data center 1:
```
node.attr.zone: zoneA
```
- Node 4, 5, and 6 in data center 2:
```
node.attr.zone: zoneB
```
With this example configuration, a new attribute called zone is created for the allocation awareness, and it is configured with the values zoneA and zoneB.
When each opensearch.yaml file has been changed, start the OpenSearch service again.

For Debian-based systems, you can use following command:
```
sudo systemctl start opensearch.service
```

Notify the OpenSearch cluster that this has been configured. You can do this with a PUT message.

This can be done from Kibana or from a Postman session:

PUT http://[IP of node]:9200/_cluster/settings
{ 
    "persistent": 
        { 
            "cluster.routing.allocation.awareness.attributes" : "zone" 
        } 
}

The OpenSearch cluster will now start moving data. Depending on how much data is already stored in your database, this can take a while.

Table of Contents

Configuring a multiple data center OpenSearch cluster

Important

Tip

Configuring allocation awareness