mate szalay-beko <> in hadoop

HADOOP-16579. Upgrade to Curator 4.2.0 and ZooKeeper 3.5.5 (#1656). Contributed by Norbert Kalmár, Mate Szalay-Beko

* HADOOP-16579 - Upgrade to Apache Curator 4.2.0 and ZooKeeper 3.5.5

- Add a static initializer for the unit tests using ZooKeeper to enable

the four-letter-words diagnostic telnet commands. (this is an interface

that become disabled by default, so to keep the ZooKeeper 3.4.x behavior

we enabled it for the tests)

- Also fix ZKFailoverController to look for relevant fail-over ActiveAttempt

records. The new ZooKeeper seems to respond quicker during the fail-over

tests than the ZooKeeper, so we made sure to catch all the relevant records

by adding a new parameter to ZKFailoverontroller.waitForActiveAttempt().

Co-authored-by: Norbert Kalmár <>