Force replication

Elastic Stack Elasticsearch
1

Hi there!

I started a new fresh Elasticsearch (7.9) cluster with sample flights data.

If I look up for the "number_of_replicas" setting of this index, I get 1. And, if I try to use the cat/shards API, I see one primary replicas one of my nodes and the other replica on other node.

Now, I want to modify the number_of_replicas from 1 to 2. When I do so, everything seems fine but I was excepting, into the /cat/shards API, to see a new replica and it's not the case.

Did I misunderstood the concept of replicas? Or maybe there is some time between the change of parameter and the moment the data is actually replicated?

Best regards,

2

You can never have more than one copy of a shard (primary/replica) per node so it will depend on the number of data nodes you have in the cluster.

3

I have 4 data nodes in my cluster

4

Can you share the output and how you changed the setting?

5

Thanks for the idea!!

The problem was the command I used to change the number of replicas

Instead of :

PUT /kibana_sample_data_ecommerce/_settings
{
"index" : {
"number_of_replicas" : 2
}
}

I had to use:

PUT /kibana_sample_data_ecommerce/_settings
{
"index" : {
"number_of_replicas" : 2,
"auto_expand_replicas": false
}
}

Now it's better!