There's a new version of Apache Curator, the Java/JVM client library for Apache ZooKeeper. Zookeeper is a distributed  coordination service. The new release of Curator adds support for TTL Nodes, and a strongly typed DSL.

Curator includes a high-level API framework and utilities to make using Apache ZooKeeper easier and more reliable. It also includes recipes for common use cases and extensions such as service discovery and a Java 8 asynchronous DSL.

ZooKeeper has been developed by Apache for developing and maintaining an open-source server which enables highly reliable distributed coordination. It is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services. All of these kinds of services are used in some form or another by distributed applications. ZooKeeper has Java and C interfaces for the applications themselves. A variety of client bindings is available for a number of languages including Python, Ruby and Go.

Curator is a set of Java libraries that make using Apache ZooKeeper much easier. Although ZooKeeper does comes bundled with a Java client, using it is quite tricky and can be error prone.

Curator consists of three components that build on each other. Curator Client is a replacement for the bundled ZooKeeper class that takes care of some low-level housekeeping and provides some useful utilities. Curator Framework is a high-level API that greatly simplifies using ZooKeeper. It adds many features that build on ZooKeeper and handles the complexity of managing connections to the ZooKeeper cluster and retrying operations. Curator Recipes consists of implementations of some of the common ZooKeeper "recipes". Additionally, Curator Test is included which includes utilities to help with unit testing ZooKeeper-based applications.

The main benefits of Curator are the simplified API; the automatic ZooKeeper connection management with retries; and better ZooKeeper recipe handling, including a set of complete, well-tested ZooKeeper recipes, and a framework that makes it easier to write new ZooKeeper recipes.

The updates to Curator start with support for TTL Nodes. ZooKeeper TTL (Time-to-live) nodes let you create and use nodes that are not tied to a session but that will expire automatically if action is not taken by some client within a time window. They were recently introduced to ZooKeeper and are now supported by Curator.

The next improvement is a new strongly typed, modeled DSL (Domain Specific Language). Until now, all of Curator's CRUD methods worked with raw byte arrays. The addition makes it possible to use strongly typed models.

The addition of the DSL gave rise to the other main improvement, a framework for data migration so developers can import or migrate data models. 

More Information

Curator Site

ZooKeeper Site

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