Swtiching from Java 6 to Java 7 on Hadoop 2.2.0

[Adam Kawa <ka...@gmail.com>]

Hi All!

We are about to upgrade the Java version of our Hadoop cluster (Hadoop
2.2.0). Just would like to ask about your recommendations and experience:

(A) Should we schedule a downtime of a whole cluster and then upgrade Java
everywhere (all Hadoop projects e.g. HDFS, YARN, Pig, Hive, Sqoop etc)

or

(B) Can we do a rolling upgrade to avoid downtime (this means that we would
run some nodes/projects on Java 6 talking to nodes/projects running on Java
7).

According to our initial research, (A) is generally recommended (because
some libraries can have incompatible APIs between their java 7 and java 6
versions e.g. Google Guavaa), but we are curious if there are any ways to
make (B) happen.

Cheers!
Adam