Moved the requirement for memory visibility of a Reducers internal state to the framework by piggybacking it to an internal field
fixed checkstyle
Changed position for the happens-before
Update MR-Introduction.md

Fixed documentation notice on version
Update Reducer.java

Fixed Javadoc as well
Fixed java.lang.IllegalArgumentException: Target cannot be null!. This was caused by the node.masterAddress being null.
This can happen after a cluster merge in the window of time between masterAddresses being cleared and repopulated.
Merge pull request #3868 from noctarius/mapreduce-issue-3866-maintenance

Moved the requirement for memory visibility of a Reducers internal state
backport: add replicated map to spring configuration
checkstyle fix
terminate the node since there is no need to wait for backups.fixes #3957
Merge pull request #4116 from mesutcelik/fix/3.3/3966

backport: add replicated map to spring configuration
Merge pull request #4109 from atlassian/nullpointerexception-in-hasongoingmigrationmaster

Fixed java.lang.IllegalArgumentException: Target cannot be null! This was caused by the node.masterAddress being null.
Merge remote-tracking branch 'hz/maintenance-3.x' into maintenance-3.x-seeburger