Pros of ZooKeeper

• More comprehensive and feature-rich distributed coordination service
• Actively maintained by Apache with regular updates and improvements
• Extensive documentation and community support

Cons of ZooKeeper

• Higher complexity and steeper learning curve
• Requires more resources and infrastructure to set up and maintain
• May be overkill for simpler use cases where a lightweight client suffices

Code Comparison

ZooKeeper:

ZooKeeper zk = new ZooKeeper("localhost:2181", 3000, new Watcher() {
    public void process(WatchedEvent we) {}
});
zk.create("/mynode", "mydata".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

ZkClient:

ZkClient zkClient = new ZkClient("localhost:2181", 10000);
zkClient.createPersistent("/mynode", "mydata");

ZooKeeper provides a more low-level API with explicit handling of connections and watchers, while ZkClient offers a simpler, more abstracted interface for common operations. ZooKeeper is better suited for complex distributed systems requiring fine-grained control, whereas ZkClient is more appropriate for simpler use cases or as a convenient wrapper around ZooKeeper functionality.

Pros of Curator

• More comprehensive and feature-rich ZooKeeper client library
• Actively maintained with regular updates and bug fixes
• Provides high-level abstractions and utilities for common ZooKeeper operations

Cons of Curator

• Steeper learning curve due to more complex API
• Larger dependency footprint compared to ZkClient
• May be overkill for simple ZooKeeper interactions

Code Comparison

ZkClient example:

ZkClient zkClient = new ZkClient("localhost:2181", 10000);
zkClient.createPersistent("/myPath", "myData");
String data = zkClient.readData("/myPath");

Curator example:

CuratorFramework client = CuratorFrameworkFactory.newClient("localhost:2181", new ExponentialBackoffRetry(1000, 3));
client.start();
client.create().forPath("/myPath", "myData".getBytes());
byte[] data = client.getData().forPath("/myPath");

Summary

Curator offers a more robust and feature-rich solution for ZooKeeper interactions, with active maintenance and a comprehensive API. However, it comes with a steeper learning curve and larger footprint. ZkClient provides a simpler interface for basic ZooKeeper operations but lacks some advanced features and ongoing development. The choice between the two depends on the complexity of your ZooKeeper usage and your project requirements.

Pros of Commons

• More comprehensive library with a wider range of utilities and components
• Better maintained with more recent updates and active community support
• Includes additional features like stats collection and service management

Cons of Commons

• Larger codebase and dependencies, potentially increasing complexity
• May include unnecessary components for projects only needing ZooKeeper functionality
• Steeper learning curve due to broader scope

Code Comparison

ZKClient:

ZkClient zkClient = new ZkClient("localhost:2181", 10000);
String data = zkClient.readData("/mypath");
zkClient.close();

Commons:

CuratorFramework client = CuratorFrameworkFactory.newClient("localhost:2181", new ExponentialBackoffRetry(1000, 3));
client.start();
byte[] data = client.getData().forPath("/mypath");
client.close();

Summary

While ZKClient focuses specifically on ZooKeeper client functionality, Commons offers a broader set of utilities and components for distributed systems. Commons provides more features and active maintenance but may be overkill for simple ZooKeeper interactions. ZKClient offers a simpler API for basic ZooKeeper operations, while Commons (using Curator) provides more robust connection handling and additional features.

Pros of Exhibitor

• Provides a web UI for ZooKeeper management and monitoring
• Offers automatic instance management and backup/restore features
• Includes a REST API for programmatic access to ZooKeeper operations

Cons of Exhibitor

• More complex setup and configuration compared to zkclient
• Requires additional infrastructure to run (e.g., web server)
• May be overkill for simple ZooKeeper client needs

Code Comparison

zkclient:

ZkClient zkClient = new ZkClient("localhost:2181", 10000, 10000, new SerializableSerializer());
zkClient.createPersistent("/myPath", "myData");
String data = zkClient.readData("/myPath");

Exhibitor:

ExhibitorRestClient client = new ExhibitorRestClient("http://localhost:8080");
client.putNode("/myPath", "myData".getBytes(), CreateMode.PERSISTENT);
byte[] data = client.getData("/myPath");

Both libraries provide methods for interacting with ZooKeeper, but Exhibitor offers a REST-based approach, while zkclient uses a more direct Java API. Exhibitor's code requires setting up the Exhibitor server separately, whereas zkclient connects directly to ZooKeeper.