NIFI-3214: Added fetch and replace to DistributedMapCache

[ijokarumawak]

There's no Processor that utilizes these new cache operations yet, but will be added by JIRA-3216. To test client and server communication, please use org.apache.nifi.distributed.cache.server.TestServerAndClient test class in nifi-distributed-cache-server project. If you need to test it on Mac OS X, then you also have to comment out these lines. Sometime it fails due to JVM issue but sometime it works:

Assume.assumeFalse("test is skipped due to build environment being OS X with JDK 1.8. See https://issues.apache.org/jira/browse/NIFI-437",
    SystemUtils.IS_OS_MAC && SystemUtils.IS_JAVA_1_8);

• Using fetch and replace together can provide optimistic locking for concurrency control.
• Added fetch to get cache entry with its meta data such as revision number.
• Added replace to update cache only if it has not been updated.
• Added Map Cache protocol version 2 for those new operations.
• Existing operations such as get or put can work with protocol version 1.

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[bbende]

Reviewing...

[bbende]

+1 Verified build passes with contrib-check, tested the Wait/Notify processors to test original cache functionality, code looks good, will merge to master, thanks Koji!