Dec 21, 2017: [EN][Elasticsearch] Knobs to turn for better indexing performance

You have a high volume logging use case and have followed these recommendations:

What other knobs can you turn to improve indexing performance?

You can find more details here.

If your use case can tolerate increased risk of data loss in event of hardware failures, these options will push the write througput even further.

  • Boost index.translog.flush_threshold_size. Once the translog reaches the specified size, a flush will take place. Defaults 512mb.
  • Set index.translog.durability to async. This setting is risky as all acknowledged writes since the last commit will be discarded if a hardware failure should occur. Depending on the use case, this may be worth considering.

All except indices.memory.index_buffer_size are index level settings and dynamically configurable. Also, you can add them to an index template to make them defaults for all indices matching the index-patterns. For example,

PUT _template/logs
  "order": 0,
  "index_patterns": "logs-*",
  "settings": {
    "refresh_interval": "30s",
    "number_of_shards": "3",
    "translog": {
      "flush_threshold_size": "1gb",
      "durability": "async"
    "unassigned": {
      "node_left": {
        "delayed_timeout": "5m"
    "query": {
      "default_field": "message"
    "number_of_replicas": "1"
  "mappings": {
    "doc": {
      "_field_names": {
        "enabled": false

And what does the future hold for better indexing performance? In the up and coming Elasticsearch version 7, we are working towards an intelligent refresh, where we will skip the refresh on a shard that has not been searched on for a period of time (30s by default) and perform the refresh at the next scheduled interval if a search request should arrive for the shard.