| /** |
| * 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.ipc; |
| |
| import java.util.ArrayList; |
| import java.util.Collection; |
| |
| import com.google.common.base.Joiner; |
| import com.google.common.collect.HashMultimap; |
| import com.google.common.collect.Multimap; |
| |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * Used to registry custom methods to refresh at runtime. |
| * Each identifier maps to one or more RefreshHandlers. |
| */ |
| @InterfaceStability.Unstable |
| public class RefreshRegistry { |
| public static final Logger LOG = |
| LoggerFactory.getLogger(RefreshRegistry.class); |
| |
| // Used to hold singleton instance |
| private static class RegistryHolder { |
| @SuppressWarnings("All") |
| public static RefreshRegistry registry = new RefreshRegistry(); |
| } |
| |
| // Singleton access |
| public static RefreshRegistry defaultRegistry() { |
| return RegistryHolder.registry; |
| } |
| |
| private final Multimap<String, RefreshHandler> handlerTable; |
| |
| public RefreshRegistry() { |
| handlerTable = HashMultimap.create(); |
| } |
| |
| /** |
| * Registers an object as a handler for a given identity. |
| * Note: will prevent handler from being GC'd, object should unregister itself |
| * when done |
| * @param identifier a unique identifier for this resource, |
| * such as org.apache.hadoop.blacklist |
| * @param handler the object to register |
| */ |
| public synchronized void register(String identifier, RefreshHandler handler) { |
| if (identifier == null) { |
| throw new NullPointerException("Identifier cannot be null"); |
| } |
| handlerTable.put(identifier, handler); |
| } |
| |
| /** |
| * Remove the registered object for a given identity. |
| * @param identifier the resource to unregister |
| * @return the true if removed |
| */ |
| public synchronized boolean unregister(String identifier, RefreshHandler handler) { |
| return handlerTable.remove(identifier, handler); |
| } |
| |
| public synchronized void unregisterAll(String identifier) { |
| handlerTable.removeAll(identifier); |
| } |
| |
| /** |
| * Lookup the responsible handler and return its result. |
| * This should be called by the RPC server when it gets a refresh request. |
| * @param identifier the resource to refresh |
| * @param args the arguments to pass on, not including the program name |
| * @throws IllegalArgumentException on invalid identifier |
| * @return the response from the appropriate handler |
| */ |
| public synchronized Collection<RefreshResponse> dispatch(String identifier, String[] args) { |
| Collection<RefreshHandler> handlers = handlerTable.get(identifier); |
| |
| if (handlers.size() == 0) { |
| String msg = "Identifier '" + identifier + |
| "' does not exist in RefreshRegistry. Valid options are: " + |
| Joiner.on(", ").join(handlerTable.keySet()); |
| |
| throw new IllegalArgumentException(msg); |
| } |
| |
| ArrayList<RefreshResponse> responses = |
| new ArrayList<RefreshResponse>(handlers.size()); |
| |
| // Dispatch to each handler and store response |
| for(RefreshHandler handler : handlers) { |
| RefreshResponse response; |
| |
| // Run the handler |
| try { |
| response = handler.handleRefresh(identifier, args); |
| if (response == null) { |
| throw new NullPointerException("Handler returned null."); |
| } |
| |
| LOG.info(handlerName(handler) + " responds to '" + identifier + |
| "', says: '" + response.getMessage() + "', returns " + |
| response.getReturnCode()); |
| } catch (Exception e) { |
| response = new RefreshResponse(-1, e.getLocalizedMessage()); |
| } |
| |
| response.setSenderName(handlerName(handler)); |
| responses.add(response); |
| } |
| |
| return responses; |
| } |
| |
| private String handlerName(RefreshHandler h) { |
| return h.getClass().getName() + '@' + Integer.toHexString(h.hashCode()); |
| } |
| } |