Introducing Apache ZooKeeper

Apache ZooKeeper is a software project of the Apache Software Foundation; it provides an open source solution to the various coordination problems in large distributed systems. ZooKeeper was originally developed at Yahoo!

ZooKeeper, as a centralized coordination service, is distributed and highly reliable, running on a cluster of servers called a ZooKeeper ensemble. Distributed consensus, group management, presence protocols, and leader election are implemented by the service so that the applications do not need to reinvent the wheel by implementing them on their own. On top of these, the primitives exposed by ZooKeeper can be used by applications to build much more powerful abstractions to solve a wide variety of problems. We will dive deeper into these concepts in Chapter 4, Performing Common Distributed System Tasks.

Apache ZooKeeper is implemented in Java. It ships with C, Java, Perl, and Python client bindings. Community-contributed client libraries are available for a plethora of languages such as Go, Scala, Erlang, and so on.

Apache ZooKeeper is widely used by a large number of organizations, such as Yahoo! Inc., Twitter, Netflix, and Facebook, in their distributed application platforms as a coordination service. We will discuss more about how ZooKeeper is used in the real world in Chapter 7, ZooKeeper in Action.