Description
Kibana uses Client#child to create an instance of the Elasticsearch client that has the authentication headers for the current end-user. As such, almost every single HTTP request to Kibana will end up calling Client#child. While doing some load testing of Kibana, the performance of Client#child is looking like a bottleneck.
During a load-test where 1000 users hit a simple HTTP Kibana API which performs authentication, I'm seeing approximately 5% of the CPU time being spent within Client#child:
The biggest culprits appear to be the use of Object.assign and ESAPI.
There are some situations where Kibana can not call Client#child until it's absolutely needed, which definitely helps, but if we can optimize the performance of Client#child it will greatly help the general performance of Kibana.
If it's not feasible to improve the performance of Client#child, Kibana can also potentially take advantage of the overloaded methods which support the TransportRequestOptions, but there are some potential complications with this approach.