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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.htrace;
import org.htrace.impl.AlwaysSampler;
import org.htrace.impl.NeverSampler;
/**
* Extremely simple callback to determine the frequency that an action should be
* performed.
*
* 'T' is the object type you require to create a more advanced sampling
* function. For example if there is some RPC information in a 'Call' object,
* you might implement Sampler. Then when the RPC is received you can call
* one of the Trace.java functions that takes the extra 'info' parameter, which
* will be passed into the next function you implemented.
*
* For the example above, the next(T info) function may look like this
*
* public boolean next(T info){
* if (info == null) {
* return false;
* } else if (info.getName().equals("get")) {
* return Math.random() > 0.5;
* } else if (info.getName().equals("put")) {
* return Math.random() > 0.25;
* } else {
* return false;
* }
* }
* This would trace 50% of all gets, 75% of all puts and would not trace any other requests.
*/
public interface Sampler {
public static final Sampler ALWAYS = AlwaysSampler.INSTANCE;
public static final Sampler NEVER = NeverSampler.INSTANCE;
public boolean next(T info);
}