| /** |
| * 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 com.twitter.distributedlog.client.routing; |
| |
| import com.google.common.collect.ImmutableSet; |
| import com.twitter.distributedlog.service.DLSocketAddress; |
| |
| /** |
| * Watch on server set changes. |
| */ |
| public interface ServerSetWatcher { |
| |
| /** |
| * Exception thrown when failed to monitor serverset. |
| */ |
| class MonitorException extends Exception { |
| |
| private static final long serialVersionUID = 392751505154339548L; |
| |
| public MonitorException(String msg) { |
| super(msg); |
| } |
| |
| public MonitorException(String msg, Throwable cause) { |
| super(msg, cause); |
| } |
| } |
| |
| /** |
| * An interface to an object that is interested in receiving notification whenever the host set changes. |
| */ |
| interface ServerSetMonitor { |
| |
| /** |
| * Called when either the available set of services changes. |
| * |
| * <p>It happens either when a service dies or a new INSTANCE comes on-line or |
| * when an existing service advertises a status or health change. |
| * |
| * @param hostSet the current set of available ServiceInstances |
| */ |
| void onChange(ImmutableSet<DLSocketAddress> hostSet); |
| } |
| |
| /** |
| * Registers a monitor to receive change notices for this server set as long as this jvm process is alive. |
| * |
| * <p>Blocks until the initial server set can be gathered and delivered to the monitor. |
| * The monitor will be notified if the membership set or parameters of existing members have |
| * changed. |
| * |
| * @param monitor the server set monitor to call back when the host set changes |
| * @throws MonitorException if there is a problem monitoring the host set |
| */ |
| void watch(final ServerSetMonitor monitor) throws MonitorException; |
| } |