Just linking a discussion we had one and a half years back on the same [1], considering nothing has changed since then because Java 7 was EOLed in July 2015 and Phoenix 5.0 was also out, it majorly comes to the point of the inconvenience of working on old code style and extra efforts required to create patches for each branch.
Let's say if we decide to upgrade to Java8(Option 3), don't we require the following changes? * Major version upgrade from 4.x-HBase-1.x to 5.x-HBase-1.x:- As upgrading 4.x branches to Java8 breaks the compatibility with HBase and Java runtime, we need to ensure that we adhere to dependency compatibility between the minor releases as it is expected that Phoenix minor upgrade should be just a server jar drop and a restart (even though we don't explicit covers Java runtime in our backward compatibility [2] as HBase does[3] but people are used to it now) * Release Notes and convenience libraries:- Though we would say that it is compatible with HBase version 1.x but require a Java8, so we need to be explicit with our convenience libraries as well , like append "jdk8" to a name or something similar (phoenix-server-HBase-1.x-jdk8.jar). And also provide clarity on the version upgrade * Avoiding issues during runtime:- Though JAVA8 and JAVA7 are said to be binary compatible and are expected to be fine in Java8 runtime but it has been called out there are rare instances which can cause issues due to some incompatibilities between JRE and JDK[4]. (As Andrew also called out and might have observed the same) Though I agreed with Istvan that creating multiple patches and dealing with change in code style every time we switch branches has put additional load on the contributor but IMHO, we should wait for HBase-1.x to upgrade Java before we do it to avoid the some of the issues listed above related to Option 3. Option2 would be preferred at the time when we decide on whether we want to diverge from feature parity in our major releases and we do only limited fixes for 4.x branch. So basically I'm also in favor of Option 1 (continuing Java 7 for HBase-1.x and code style as much possible for 5.x). [1] https://lists.apache.org/thread.html/970db0b5cb0560c49654e450aafb8fb759596384cefe4f02808e80cc%40%3Cdev.phoenix.apache.org%3E [2]http://phoenix.apache.org/upgrading.html [3] https://hbase.apache.org/book.html#hbase.versioning [4] https://www.oracle.com/technetwork/java/javase/8-compatibility-guide-2156366.html#A999387 Regards, Ankit Singhal
