This JIRA is used to log JDK-related issues that often cause Spark to throw weird runtime exceptions or be permanently unresponsive.
For Spark users, these issues tend to be very common but difficult to locate. When users encounter such questions, the JIRA may help them get quick answers when googling. The answers may often simply require them to upgrade the JDK versions.
These issues are also difficult for the community to deal with in Spark's code, and even maintaining documentation for troubleshooting in the code can be a challenge. As a distributed JVM application, problems with the JDK can take many forms.
So JIRA might be a good choice for documenting these problems