com.transferwise.envoy.xds.api.DiscoveryServiceManagerMetrics Maven / Gradle / Ivy

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package com.transferwise.envoy.xds.api;

import java.util.function.Supplier;

/**
 * Records metrics about state update latencies for Envoy clients.
 *
 * One instance will be instantiated per discovery stream.
 * Thread safety: unsafe! The caller must make sure synchronization happens.
 * The synchronization implemented by caller may only extend to the specific instance
 * but not globally over all instances. So the implementation must arrange any internal
 * synchronization to a shared metric storage, if needed.
 * 
 */
public interface DiscoveryServiceManagerMetrics {

    DiscoveryServiceManagerMetrics NOOP_METRICS = new NoopMetrics();
    Supplier METRICS_DISABLED = () -> NOOP_METRICS;

    default void close() {

    }

    /**
     * This is called when we begin pushing messages generated by a state update towards a client.
     * onPushBegin() and onPushComplete() must be called in pairs, and must not be called after close().
     */
    default void onPushBegin() {

    }

    /**
     * This is called once client has acked all of the messages sent to it for a state update.
     * onPushBegin() and onPushComplete() must be called in pairs, and must not be called after close().
     */
    default void onPushComplete() {

    }

    /**
     * This is called when a discovery service is expecting an ack.
     */
    default void onAwaitingAck() {

    }

    /**
     * This is called when envoy acks an outstanding message.
     */
    default void onMessageAcked() {

    }

    class NoopMetrics implements DiscoveryServiceManagerMetrics {
    }

}