| /* |
| * 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.apache.htrace; |
| |
| import org.apache.htrace.impl.AlwaysSampler; |
| import org.apache.htrace.impl.NeverSampler; |
| |
| /** |
| * Extremely simple callback to determine the frequency that an action should be |
| * performed. |
| * <p/> |
| * '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<Call>. 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. |
| * <p/> |
| * For the example above, the next(T info) function may look like this |
| * <p/> |
| * 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<T> { |
| |
| public static final Sampler<?> ALWAYS = AlwaysSampler.INSTANCE; |
| public static final Sampler<?> NEVER = NeverSampler.INSTANCE; |
| |
| public boolean next(T info); |
| |
| } |