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/*
* Copyright DataStax, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.datastax.driver.core;
/**
* Interface for objects that are interested in tracking the latencies of the driver queries to each
* Cassandra nodes.
*
* An implementation of this interface can be registered against a Cluster object trough the
* {@link Cluster#register} method, after which the {@link #update(Host, Statement, Exception,
* long)} method will be called after each query of the driver to a Cassandra host with the
* latency/duration (in nanoseconds) of this operation.
*/
public interface LatencyTracker {
/**
* A method that is called after each request to a Cassandra node with the duration of that
* operation.
*
*
Note that there is no guarantee that this method won't be called concurrently by multiple
* threads, so implementations should synchronize internally if need be.
*
* @param host The Cassandra host on which a request has been performed. This parameter is never
* {@code null}.
* @param statement The {@link com.datastax.driver.core.Statement} that has been executed. This
* parameter is never {@code null}.
* @param exception An {@link Exception} thrown when receiving the response, or {@code null} if
* the response was successful.
* @param newLatencyNanos the latency in nanoseconds of the operation. This latency corresponds to
* the time elapsed between when the query was sent to {@code host} and when the response was
* received by the driver (or the operation timed out, in which {@code newLatencyNanos} will
* approximately be the timeout value).
*/
public void update(Host host, Statement statement, Exception exception, long newLatencyNanos);
/**
* Gets invoked when the tracker is registered with a cluster, or at cluster startup if the
* tracker was registered at initialization with {@link
* com.datastax.driver.core.Cluster.Initializer#register(LatencyTracker)}.
*
* @param cluster the cluster that this tracker is registered with.
*/
void onRegister(Cluster cluster);
/**
* Gets invoked when the tracker is unregistered from a cluster, or at cluster shutdown if the
* tracker was not unregistered.
*
* @param cluster the cluster that this tracker was registered with.
*/
void onUnregister(Cluster cluster);
}