Package org.apache.curator.framework.state

Class CircuitBreakingConnectionStateListener

  • All Implemented Interfaces:
    ConnectionStateListener
    public class CircuitBreakingConnectionStateListener
extends java.lang.Object
implements ConnectionStateListener

    A decorator/proxy for connection state listeners that adds circuit breaking behavior. During network outages ZooKeeper can become very noisy sending connection/disconnection events in rapid succession. Curator recipes respond to these messages by resetting state, etc. E.g. LeaderLatch must delete its lock node and try to recreate it in order to try to re-obtain leadership, etc.

    This noisy herding can be avoided by using the circuit breaking listener decorator. When it receives ConnectionState.SUSPENDED, the circuit becomes "open" (based on the provided RetryPolicy) and will ignore future connection state changes until RetryPolicy timeout has elapsed. Note: however, if the connection goes from ConnectionState.SUSPENDED to ConnectionState.LOST the first LOST state is sent.

    When the circuit decorator is closed, all connection state changes are forwarded to the managed listener. When the first disconnected state is received, the circuit becomes open. The state change that caused the circuit to open is sent to the managed listener and the RetryPolicy will be used to get a delay amount. While the delay is active, the decorator will store state changes but will not forward them to the managed listener (except, however, the first time the state changes from SUSPENDED to LOST). When the delay elapses, if the connection has been restored, the circuit closes and forwards the new state to the managed listener. If the connection has not been restored, the RetryPolicy is checked again. If the RetryPolicy indicates another retry is allowed the process repeats. If, however, the RetryPolicy indicates that retries are exhausted then the circuit closes - if the current state is different than the state that caused the circuit to open it is forwarded to the managed listener.

    • Constructor Detail

      • CircuitBreakingConnectionStateListener

        public CircuitBreakingConnectionStateListener​(CuratorFramework client,
                                              ConnectionStateListener listener,
                                              org.apache.curator.RetryPolicy retryPolicy)
        Parameters:
        client - Curator instance
        listener - listener to manage
        retryPolicy - breaking policy to use

      • CircuitBreakingConnectionStateListener

        public CircuitBreakingConnectionStateListener​(CuratorFramework client,
                                              ConnectionStateListener listener,
                                              org.apache.curator.RetryPolicy retryPolicy,
                                              java.util.concurrent.ScheduledExecutorService service)
        Parameters:
        client - Curator instance
        listener - listener to manage
        retryPolicy - breaking policy to use
        service - scheduler to use