| /* |
| * MetricsContext.java |
| * |
| * 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.metrics; |
| |
| import java.io.IOException; |
| import java.util.Collection; |
| import java.util.Map; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.apache.hadoop.metrics.spi.OutputRecord; |
| |
| /** |
| * The main interface to the metrics package. |
| */ |
| @InterfaceAudience.Private |
| @InterfaceStability.Evolving |
| public interface MetricsContext { |
| |
| /** |
| * Default period in seconds at which data is sent to the metrics system. |
| */ |
| public static final int DEFAULT_PERIOD = 5; |
| |
| /** |
| * Initialize this context. |
| * @param contextName The given name for this context |
| * @param factory The creator of this context |
| */ |
| public void init(String contextName, ContextFactory factory); |
| |
| /** |
| * Returns the context name. |
| * |
| * @return the context name |
| */ |
| public abstract String getContextName(); |
| |
| /** |
| * Starts or restarts monitoring, the emitting of metrics records as they are |
| * updated. |
| */ |
| public abstract void startMonitoring() |
| throws IOException; |
| |
| /** |
| * Stops monitoring. This does not free any data that the implementation |
| * may have buffered for sending at the next timer event. It |
| * is OK to call <code>startMonitoring()</code> again after calling |
| * this. |
| * @see #close() |
| */ |
| public abstract void stopMonitoring(); |
| |
| /** |
| * Returns true if monitoring is currently in progress. |
| */ |
| public abstract boolean isMonitoring(); |
| |
| /** |
| * Stops monitoring and also frees any buffered data, returning this |
| * object to its initial state. |
| */ |
| public abstract void close(); |
| |
| /** |
| * Creates a new MetricsRecord instance with the given <code>recordName</code>. |
| * Throws an exception if the metrics implementation is configured with a fixed |
| * set of record names and <code>recordName</code> is not in that set. |
| * |
| * @param recordName the name of the record |
| * @throws MetricsException if recordName conflicts with configuration data |
| */ |
| public abstract MetricsRecord createRecord(String recordName); |
| |
| /** |
| * Registers a callback to be called at regular time intervals, as |
| * determined by the implementation-class specific configuration. |
| * |
| * @param updater object to be run periodically; it should updated |
| * some metrics records and then return |
| */ |
| public abstract void registerUpdater(Updater updater); |
| |
| /** |
| * Removes a callback, if it exists. |
| * |
| * @param updater object to be removed from the callback list |
| */ |
| public abstract void unregisterUpdater(Updater updater); |
| |
| /** |
| * Returns the timer period. |
| */ |
| public abstract int getPeriod(); |
| |
| /** |
| * Retrieves all the records managed by this MetricsContext. |
| * Useful for monitoring systems that are polling-based. |
| * |
| * @return A non-null map from all record names to the records managed. |
| */ |
| Map<String, Collection<OutputRecord>> getAllRecords(); |
| } |