Elasticsearch 7.5.2 cluster is creating only one shard for an index by default

Question

I have a newly setup Elasticsearch 7.5.2 cluster. When I create an index, only one shard is created default for it.

My cluster strategy is as below:

Total Nodes: 5
--------------
Node 1 & Node 2 - Master Only
Node 3          - Master & Data Node
Node 4 & Node 5 - Data Only

Could not find any cluster setting that is restricting the shards for index creation. Is the issue with cluster strategy or am I missing any settings here?.

Please help me to find the the issue.

Answer 1

Earlier Elasticsearch had default number of primary shards to 5, which is changed from Elasticsearch 7.X, which you are using, hence you are seeing just 1 primary shard.

Elasticsearch link for this change and more info on this SO answer.

Apart from API which is applicable on a particular index, which @Kamal already mentioned, you can specify this setting in your elasticsearch.yml , which would be effective on every index created until you override using the API call.

Config to add in your elasticsearch.yml

index.number_of_shards: {your desired number of shards}

Note: This is for primary shards that can't be changed dynamically, so be cautious of setting this, Unlike the number of replicas which can be changed dynamically.

Answer 2

That is correct. Post version 7, Elasticsearch by default creates index with shard size 1 as mentioned here

You can always specify the index shard using the below settings, while creating the index.

PUT <your_index_name>
{
    "settings" : {
        "index" : {
            "number_of_shards" : 5
        }
    }
}

Hope this helps!