How to settings a elasticsearch cluster correctly

Elastic Stack Elasticsearch
1

Hello!
According to the terms of reference, I have to set up a cluster of five nodes.

I have a number of questions.

  1. Can I specify one of the nodes simultaneously as a master node and as a data node?

  2. If I specified one master node (coordinator), what happens if it fails? Will other nodes choose a new coordinator? How to properly configure the nodes so that when the coordinator fails, they choose a new one from the remaining four nodes?

2

You can have 3 nodes as master & data

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3

Okay, I'm just worried that if one of the three masters fails, then a situation might occur: Split brain. Am I correct in understanding that when two masters work, this can happen? If so, how can this situation be avoided?

4

Three master eligible nodes protect you from split brain scenarios.

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6

I understand, but if one of the three fails, what then?

7

Then the remaining two can still form a majority until the failed node returns.

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8

Well thank you!
I found the information I needed:
In Elasticsearch, setting node.master: true does not mean that this node is a master, it just says that it can be selected as a master node.

Is it really so?

9

Yes. Each cluster only has one master node at any time but this need to be able to change if you want HA which is why you need 3 or more master eligible nodes.

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10

Thank!

11

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