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/*
* Copyright (C) 2012 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 object 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
* {@code update} 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 thread, so implementations should synchronize
* internally if need be.
*
* @param host the Cassandra host on which a request has been performed.
* @param newLatencyNanos the latency in nanoseconds of the operation. This
* latency corresponds to the time elapsed between when the query was send
* 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, long newLatencyNanos);
}