Thanks as always for the feedback everyone. Some inline comments to Arun's email, as his were the most extensive:
> Given that we already agreed to put in JDK7 in 2.7, and that the > classpath is a fairly minor irritant given some existing solutions (e.g. a > new default classloader), how do you quantify the benefit for users? > > I looked at our thread on this topic from last time, and we (meaning at least myself and Tucu) agreed to a one-time exception to the JDK7 bump in 2.x for practical reasons. We waited for so long that we had some assurance JDK6 was on the outs. Multiple distros also already had bumped their min version to JDK7. This is not true this time around. Bumping the JDK version is hugely impactful on the end user, and my email on the earlier thread still reflects my thoughts on JDK compatibility: http://mail-archives.apache.org/mod_mbox/hadoop-common-dev/201406.mbox/%3CCAGB5D2a5fEDfBApQyER_zyhc8a4Xd_ea1wJSsxxkiAiDZO9%2BNg%40mail.gmail.com%3E Regarding classpath isolation, based on what I hear from our customers, it's still a big problem (even after the MR classloader work). The latest Jackson version bump was quite painful for our downstream projects, and the HDFS client still leaks a lot of dependencies. Would welcome more discussion of this on HADOOP-11656, Steve, Colin, and Haohui have already chimed in. Having the freedom to upgrade our dependencies at will would also be a big win for us as developers. We could just do JDK8 in hadoop-2.10 or some such, you are definitely > welcome to run the RM role for that release. > > Furthermore, I'm really concerned that this will be used as an > opportunity to further break compat in more egregious ways. > > Also, are you foreseeing more compat breaks? OTOH, if we all agree that > we should absolutely prevent compat breakages such as the client-server > wire protocol, I feel the point of a major release is kinda lost. > > Right now, the incompatible changes would be JDK8, classpath isolation, and whatever is already in trunk. I can audit these existing trunk changes when branch-3 is cut. I would like to keep this list as short as possible, to preserve wire compat and rolling upgrade. As far as major releases go, this is not one to be scared of. However, since it's incompatible, it still needs that major version bump. Best, Andrew P.S. Vinod, the shell script rewrite is incompatible. Allen intentionally excluded it from branch-2 for this reason.
