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amazon-web-serviceselasticsearchjvm

Understanding why AWS Elasticsearch GC (young and old) keeps on rising while memory pressure is not

I am trying to understand if I have an issue with my AWS Elasticsearch garbage collection time but all the memory-related issues that I find are relating to memory pressure which seems OKish.

So while I run a load test on the environment, I observe a constant rise in all GC collection time metrics, for example:

GC Young collection time

But when looking at memory pressure, I see that I am not passing the 75% mark (but getting near..) which, according to documentation, will trigger a concurrent mark & sweep.

JVM Memory pressure

So I fear that once I add more load or run a longer test, I might start seeing real issues which will have an impact on my environment. So, do I have an issue here? how should I approach rising GC time when I cant take memory dumps and see what's going on?

Solution

  • I sent a query to AWS technical support and, counter to any intuitive behavior, the values of the Young and Old Collection time and count in Elasticsearch is cumulative. This means that this value keeps increasing and does not drop down to a value of 0 until there is a node drop or node restart