Hi all, I would like to start a discussion on making Java 8 a minimum requirement for Kafka's next feature release (let's say Kafka 0.10.1.0 for now). This is the first discussion on the topic so the idea is to understand how people feel about it. If people feel it's too soon, then we can pick up the conversation again after Kafka 0.10.1.0. If the feedback is mostly positive, I will start a vote thread.
Let's start with some dates. Java 7 hasn't received public updates since April 2015[1], Java 8 was released in March 2014[2] and Java 9 is scheduled to be released in March 2017[3]. The first argument for dropping support for Java 7 is that the last public release by Oracle contains a large number of known security vulnerabilities. The effectiveness of Kafka's security features is reduced if the underlying runtime is not itself secure. The second argument for moving to Java 8 is that it adds a number of compelling features: * Lambda expressions and method references (particularly useful for the Kafka Streams DSL) * Default methods (very useful for maintaining compatibility when adding methods to interfaces) * java.util.stream (helpful for making collection transformations more concise) * Lots of improvements to java.util.concurrent (CompletableFuture, DoubleAdder, DoubleAccumulator, StampedLock, LongAdder, LongAccumulator) * Other nice things: SplittableRandom, Optional (and many others I have not mentioned) The third argument is that it will simplify our testing matrix, we won't have to test with Java 7 any longer (this is particularly useful for system tests that take hours to run). It will also make it easier to support Scala 2.12, which requires Java 8. The fourth argument is that many other open-source projects have taken the leap already. Examples are Cassandra[4], Lucene[5], Akka[6], Hadoop 3[7], Jetty[8], Eclipse[9], IntelliJ[10] and many others[11]. Even Android will support Java 8 in the next version (although it will take a while before most phones will use that version sadly). This reduces (but does not eliminate) the chance that we would be the first project that would cause a user to consider a Java upgrade. The main argument for not making the change is that a reasonable number of users may still be using Java 7 by the time Kafka 0.10.1.0 is released. More specifically, we care about the subset who would be able to upgrade to Kafka 0.10.1.0, but would not be able to upgrade the Java version. It would be great if we could quantify this in some way. What do you think? Ismael [1] https://java.com/en/download/faq/java_7.xml [2] https://blogs.oracle.com/thejavatutorials/entry/jdk_8_is_released [3] http://openjdk.java.net/projects/jdk9/ [4] https://github.com/apache/cassandra/blob/trunk/README.asc [5] https://lucene.apache.org/#highlights-of-this-lucene-release-include [6] http://akka.io/news/2015/09/30/akka-2.4.0-released.html [7] https://issues.apache.org/jira/browse/HADOOP-11858 [8] https://webtide.com/jetty-9-3-features/ [9] http://markmail.org/message/l7s276y3xkga2eqf [10] https://intellij-support.jetbrains.com/hc/en-us/articles/206544879-Selecting-the-JDK-version-the-IDE-will-run-under [11] http://markmail.org/message/l7s276y3xkga2eqf
