| /** |
| * 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.hadoop.metrics2; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| /** |
| * The metrics system interface |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Evolving |
| public abstract class MetricsSystem implements MetricsSystemMXBean { |
| |
| @InterfaceAudience.Private |
| public abstract MetricsSystem init(String prefix); |
| |
| /** |
| * Register a metrics source |
| * @param <T> the actual type of the source object |
| * @param source object to register |
| * @param name of the source. Must be unique or null (then extracted from |
| * the annotations of the source object.) |
| * @param desc the description of the source (or null. See above.) |
| * @return the source object |
| * @exception MetricsException |
| */ |
| public abstract <T> T register(String name, String desc, T source); |
| |
| /** |
| * Unregister a metrics source |
| * @param name of the source. This is the name you use to call register() |
| */ |
| public abstract void unregisterSource(String name); |
| |
| /** |
| * Register a metrics source (deriving name and description from the object) |
| * @param <T> the actual type of the source object |
| * @param source object to register |
| * @return the source object |
| * @exception MetricsException |
| */ |
| public <T> T register(T source) { |
| return register(null, null, source); |
| } |
| |
| /** |
| * @param name of the metrics source |
| * @return the metrics source (potentially wrapped) object |
| */ |
| @InterfaceAudience.Private |
| public abstract MetricsSource getSource(String name); |
| |
| /** |
| * Register a metrics sink |
| * @param <T> the type of the sink |
| * @param sink to register |
| * @param name of the sink. Must be unique. |
| * @param desc the description of the sink |
| * @return the sink |
| * @exception MetricsException |
| */ |
| public abstract <T extends MetricsSink> |
| T register(String name, String desc, T sink); |
| |
| /** |
| * Register a callback interface for JMX events |
| * @param callback the callback object implementing the MBean interface. |
| */ |
| public abstract void register(Callback callback); |
| |
| /** |
| * Requests an immediate publish of all metrics from sources to sinks. |
| * |
| * This is a "soft" request: the expectation is that a best effort will be |
| * done to synchronously snapshot the metrics from all the sources and put |
| * them in all the sinks (including flushing the sinks) before returning to |
| * the caller. If this can't be accomplished in reasonable time it's OK to |
| * return to the caller before everything is done. |
| */ |
| public abstract void publishMetricsNow(); |
| |
| /** |
| * Shutdown the metrics system completely (usually during server shutdown.) |
| * The MetricsSystemMXBean will be unregistered. |
| * @return true if shutdown completed |
| */ |
| public abstract boolean shutdown(); |
| |
| /** |
| * The metrics system callback interface (needed for proxies.) |
| */ |
| public interface Callback { |
| /** |
| * Called before start() |
| */ |
| void preStart(); |
| |
| /** |
| * Called after start() |
| */ |
| void postStart(); |
| |
| /** |
| * Called before stop() |
| */ |
| void preStop(); |
| |
| /** |
| * Called after stop() |
| */ |
| void postStop(); |
| } |
| |
| /** |
| * Convenient abstract class for implementing callback interface |
| */ |
| public static abstract class AbstractCallback implements Callback { |
| @Override public void preStart() {} |
| @Override public void postStart() {} |
| @Override public void preStop() {} |
| @Override public void postStop() {} |
| } |
| } |