Elasticsearch shows duplicated logs and poor performance in OpenShift Container Platform

Issue

• In Kibana it is sometime visible a high amount of logs for a specific period of time, specially in the .operations indices.
• It is visible duplicated logs over the time
• After the cluster has gone through a period of stress, Elasticsearch takes a lot of time to recover and indices size grow considerably
• In fluentd pods logs any of these timeout messages appear frequently:

2017-09-25 16:07:41 +0200 [warn]: buffer flush took longer time than slow_flush_log_threshold: plugin_id="object:13c4370" elapsed_time=36.999487413 slow_flush_log_threshold=20.0

2017-09-25 16:07:38 +0200 [warn]: Could not push logs to Elasticsearch, resetting connection and trying again. read timeout reached

2017-09-25 16:23:59 +0200 [warn]: temporarily failed to flush the buffer. next_retry=2017-09-25 16:20:37 +0200 error_class="Fluent::ElasticsearchOutput::ConnectionFailure" error="Could not push logs to Elasticsearch after 2 retries. read timeout reached" plugin_id="object:13c4370"