/**
* 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;
/**
* The metrics system interface
*/
public interface MetricsSystem extends MetricsSystemMXBean {
/**
* Register a metrics source
* @param <T> the type of the source
* @param source to register
* @param name of the source. Must be unique.
* @param desc the description of the source.
* @return the source
* @exception MetricsException
*/
<T extends MetricsSource> T register(String name, String desc, T source);
/**
* 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
*/
<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.
*/
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.
*/
void shutdown();
/**
* The metrics system callback interface
*/
@SuppressWarnings("PublicInnerClass")
static 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
*/
@SuppressWarnings("PublicInnerClass")
public static abstract class AbstractCallback implements Callback {
public void preStart() {}
public void postStart() {}
public void preStop() {}
public void postStop() {}
}
}