We have been noticing high CPU usage and performance degradation after migrated to Zulu OpenJDK. So can any one throw some light on it?
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Hi Varun and Erick!
Zulu is OpenJDK, so it doesn't make too much sense to say that DSE is tested on OpenJDK and that other vendor versions aren't specifically tested. OpenJDK is not a vendor, and not a vendor-specific term.
The DataStax supported platforms page says "DataStax recommends the latest build of a TCK Certified OpenJDK version 8 or supported Oracle JRE or JDK version 8." and where it goes into any detail about OpenJDK, it just says OpenJDK. It doesn't specify a vendor anywhere other than the reference to Oracle.
Here's a list of vendors that provide builds of OpenJDK, you can see which ones are TCK Certified, including Zulu: https://en.wikipedia.org/wiki/OpenJDK#OpenJDK_builds
@Erick Ramirez, if you'd like to suggest your users use a specific vendor's build of OpenJDK, you need to specify the vendor. You can't just suggest temporarily switching from Zulu to OpenJDK, because Zulu is equally OpenJDK as any other vendor's OpenJDK build.
@vkayanala_42513, what happened with your testing with Zulu? How did that get resolved? Zulu should perform the same with Cassandra as any other OpenJDK build (of the same JDK version and update level, of course). If you found that to be different, it would be unexpected and considered a bug, and we'd want to know about it and resolve it.
(From the Azul Systems support team)
@vkayanala_42513 As a general rule, any TCK-compliant JRE/JDK will work with Cassandra. As long as the Java vendor/version passes the TCK specification tests, it should work. However in practice, we are aware that users report various issues with some variants like IBM's version of Java.
For what it's worth, release-testing for open-source Apache Cassandra and even DataStax Enterprise is done on OpenJDK. That doesn't mean other vendor versions won't work -- it's just that they're not specifically tested. It's impossible to test all available variants as you'd appreciate.
My suggestion is that if you're having issues with Zulu, temporarily switch to OpenJDK and do some tests to rule out issues specific to your cluster's configuration. If you continue to have issues with Zulu, perhaps you should engage Azul for assistance. Cheers!
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