How to Enable Slow Query Logging in Elasticsearch

Problem:
You're experiencing search performance issues or suspect slow queries in your Elasticsearch cluster used with Mattermost, and want to enable slow query logging for further debugging.

Solution:

Slow query logging helps identify performance bottlenecks by logging queries and fetch phases that exceed a specified threshold. Follow the appropriate instructions based on your ES environment.

For Self-Hosted ElasticSearch Environments:

Use the following curl command to enable slow query logging for a specific index:

curl -X PUT "<ES_URL>/<index_name>/_settings?pretty" -H 'Content-Type: application/json' -d'
{
  "index.search.slowlog.threshold.query.warn": "1s",
  "index.search.slowlog.threshold.fetch.warn": "1s"
}
'

🔧 Replace <ES_URL> with your ES host and <index_name> with the name of the index you want to monitor (e.g., mattermost-index).

 For AWS OpenSearch users :

AWS provides a simplified way to enable slow query logging via the console. Please check the following doc-  https://aws.amazon.com/blogs/database/viewing-amazon-elasticsearch-service-slow-logs for the same.