The Apache Hadoop project is
a collection of many sub projects and ZooKeeper(now
a top-level project in its own) is one among them and is noticeable for its
wide applicability for building distributed systems.
ZooKeeper is a distributed, open-source coordination service for
distributed applications. Very large Hadoop clusters
can be maintained by multiple ZooKeeper servers as it ensures the availability
by never-ending services.In Hadoop project it is used
to manage master election and store other process metadata.
For example
In Hadoop we do
have many types’ nodes, master and multiple worker nodes. If by any chance
the master node fails then role of master node has to be transferred to
different node. This is done by zookeeper as it takes care of clusters by
assigning tasks to new master node
