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Comment by aorth | Hacker News Reader

> In the old cluster, we used Java 8 to run Elasticsearch which was the latest Java version supported at the time. In the new cluster, we use the bundled Java 18 version which allows us to utilize a more modern garbage collector that works better with larger heaps. We used CMS in the old cluster and use G1 in the new one.

/me cries in legacy Java 8 application.

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Makes me wonder whats holding back an upgrade?

I'm guessing they were too far behind to do nice incremental one. Pretty much every major version upgrade in the past meant reindexing and some functionality changes.

In the meldwater case yes, but was interested in the parent's reason.

You can use G1 on Java 8 with -XX:+UseG1GC

I wouldn't recommend it, however, especially with Elasticsearch. I spent a lot of time with their team debugging issues that came down to G1GC issues in those days.

On a related note, for years I had been following ShawnHeisy's wiki notes on Java / Solr. For a long time there was a HUGE warning about G1GC + Lucene (which is the underlying technology in both Solr and Elasticsearch).

https://cwiki.apache.org/confluence/display/solr/shawnheisey

Those warnings have gone away recently. Make of that what you will.

In Elasticsearch, the default has changed more than 3 years ago (since we always ship the current JDK by default): https://github.com/elastic/elasticsearch/pull/49123

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