What is the working principle of ZooKeeper?
ZooKeeper operates on a cluster model based on distributed coordination services. It is an open-source distributed coordination service mainly used for coordinating and synchronizing distributed applications.
A ZooKeeper cluster is made up of multiple servers, with one serving as the Leader and the rest as Followers. The Leader is responsible for handling client requests and syncing updates to the Follower nodes. Each node maintains a data tree in memory, similar to a file system, with the ability to store data in each node.
The working principle of ZooKeeper can be summarized in the following steps:
- The client connects to any node in the ZooKeeper cluster and sends a request.
- The Leader node in the cluster receives and processes client requests, converting the operations into transaction logs.
- The Leader node synchronizes the transaction log to the Follower node, ensuring consistency of data across all nodes.
- The client receives the response of the operation and proceeds to the next step if necessary.
- If the Leader node fails, one of the Follower nodes in the cluster will be elected as the new Leader to continue processing client requests.
ZooKeeper achieves data consistency and durability by utilizing the ZAB (ZooKeeper Atomic Broadcast) protocol. The ZAB protocol ensures the ordered consistency of transactions and considers an operation successful only after most nodes have received the transaction log.
The working principle of ZooKeeper allows it to be used for implementing distributed locks, naming services, configuration management, and other distributed application scenarios, providing a reliable coordination and synchronization mechanism for distributed systems.
