Apache Avro is a data serialization format. Avro shares many features with Google’s Protocol Buffers and Apache Thrift, including: Rich data types, Compact serialization, Support for many programming languages, Datatype evolution, also known as versioning.
Apache ZooKeeper provides operational services for a Hadoop cluster. ZooKeeper provides a distributed configuration service, a synchronization service and a naming registry for distributed systems. Distributed applications use Zookeeper to store and mediate updates to important configuration information.