We are running a somewhat untypical setup (not your usual production elasticsearch usage) of around 40 very small (single node) elasticsearch docker instances (version 7.17.3) per server.
Most instances contain very little data even the biggest ones are only a few hundred MB in disk size.
Every night at midnight (local time) we experience extremely high load caused by the ES docker containers. For about 20 seconds the CPUs are saturated and RAM is maxed out, then for about 10 seconds high disk write occurs.
The load has been high enough to occasionally freeze our (reasonably sized) server for a few minutes. The only workaround we have found is to spread out our applications to more servers but of course otherwise the servers are moreless idle.
Are there any daily cleanup jobs in elasticsearch (similar to postgres auto vacuum etc.) which are triggered by default at midnight?
If yes - is it possible to configure a different default start time (which would solve our issues)?
If no - how to find the culprit? Is there some kind of monitoring log which can be activated to catch anything causing such high load inside the ES containers?
A example monitoring graph from one of our severs.
This is the exact docker configuration we are using:
elasticsearch: # https://www.docker.elastic.co/r/elasticsearch image: docker.elastic.co/elasticsearch/elasticsearch:7.17.3 restart: unless-stopped environment: - discovery.type=single-node - xpack.security.enabled=false - http.cors.allow-origin=http://localhost:1358,http://127.0.0.1:1358 - http.cors.enabled=true - http.cors.allow-headers=X-Requested-With,X-Auth-Token,Content-Type,Content-Length,Authorization - http.cors.allow-credentials=true - cluster.routing.allocation.disk.threshold_enabled=false # Disable watermark check (safeguard which sets write only indexes on low disk space) - bootstrap.memory_lock=true - "ES_JAVA_OPTS=-Xms512m -Xmx512m" ulimits: memlock: soft: -1 hard: -1 volumes: - ./data/elastic01:/usr/share/elasticsearch/data