Total_shards_per_node on an index pattern instead of an simple index

Elastic Stack Elasticsearch
1

Hello,

I'm looking for a way to limit the number of shards per nodes on a group of index. Is it possible, may be by using index patterns ?

My situation is :

  • I have a set of 14 indexes with 12 shards for each
  • We have 10 nodes
  • I need those 14 indexes to be spread as flat as possible on the nodes, meaning 16-17 shards by nodes. However we have many other indexes in the stack, and elasticsearch sometimes changes the shards repartition for my 14 indexes (after a node falling, or because we lower the load on those 14 indexes, etc.).
  • Therefore I would love to be able to set something like
  "my-14-indexes-pattern*": {
    "settings": {
      "index.routing.allocation.total_shards_per_node": "17" 
    }

Would you have an idea to share ?
Thank you !

2

Hello,
no, total_shards_per_node is an index level setting, you cannot assign a specific value to a group of indices. You have to deal with individual index and set it to 2 (for instance) in order to avoid hotspots.
Be aware that this is a hard limit to the number of shards (primary+replica) of these indices that each data node will accept.
Out of curiosity, why 12 shards per index ? are they only primaries or does it include replica ?

3

Hello Vincent, thank you for your answer !

The thing is that the limit of 2 / index allows hotspots of 28 shards and only that destroys my performances.
I don't quite understand why ES rebalancing choses to create hotspot while my indexes are (normally) solicited in a homogeneous way. And a proof for that is that as soon as a hotspot appears, the node's latency is 3 to 4 times greater than the other nodes latencies.

We have only primaries for those indexes and 12 shards makes each shard being 50Go and this repartitions seems optimal for our performances :slight_smile:

4

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