WARNING: Version 5.1 of Elasticsearch has passed its EOL date.
This documentation is no longer being maintained and may be removed. If you are running this version, we strongly advise you to upgrade. For the latest information, see the current release documentation.
Elasticsearch uses a number of thread pools for different types of operations. It is important that it is able to create new threads whenever needed. Make sure that the number of threads that the Elasticsearch user can create is at least 2048.