001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018 package org.apache.hadoop.ha;
019
020 import org.apache.hadoop.classification.InterfaceAudience;
021 import org.apache.hadoop.classification.InterfaceStability;
022 import org.apache.hadoop.fs.CommonConfigurationKeys;
023 import org.apache.hadoop.io.retry.Idempotent;
024 import org.apache.hadoop.security.AccessControlException;
025 import org.apache.hadoop.security.KerberosInfo;
026
027 import java.io.IOException;
028
029 /**
030 * Protocol interface that provides High Availability related primitives to
031 * monitor and fail-over the service.
032 *
033 * This interface could be used by HA frameworks to manage the service.
034 */
035 @KerberosInfo(
036 serverPrincipal=CommonConfigurationKeys.HADOOP_SECURITY_SERVICE_USER_NAME_KEY)
037 @InterfaceAudience.Public
038 @InterfaceStability.Evolving
039 public interface HAServiceProtocol {
040 /**
041 * Initial version of the protocol
042 */
043 public static final long versionID = 1L;
044
045 /**
046 * An HA service may be in active or standby state. During startup, it is in
047 * an unknown INITIALIZING state. During shutdown, it is in the STOPPING state
048 * and can no longer return to active/standby states.
049 */
050 public enum HAServiceState {
051 INITIALIZING("initializing"),
052 ACTIVE("active"),
053 STANDBY("standby"),
054 STOPPING("stopping");
055
056 private String name;
057
058 HAServiceState(String name) {
059 this.name = name;
060 }
061
062 @Override
063 public String toString() {
064 return name;
065 }
066 }
067
068 public static enum RequestSource {
069 REQUEST_BY_USER,
070 REQUEST_BY_USER_FORCED,
071 REQUEST_BY_ZKFC;
072 }
073
074 /**
075 * Information describing the source for a request to change state.
076 * This is used to differentiate requests from automatic vs CLI
077 * failover controllers, and in the future may include epoch
078 * information.
079 */
080 public static class StateChangeRequestInfo {
081 private final RequestSource source;
082
083 public StateChangeRequestInfo(RequestSource source) {
084 super();
085 this.source = source;
086 }
087
088 public RequestSource getSource() {
089 return source;
090 }
091 }
092
093 /**
094 * Monitor the health of service. This periodically called by the HA
095 * frameworks to monitor the health of the service.
096 *
097 * Service is expected to perform checks to ensure it is functional.
098 * If the service is not healthy due to failure or partial failure,
099 * it is expected to throw {@link HealthCheckFailedException}.
100 * The definition of service not healthy is left to the service.
101 *
102 * Note that when health check of an Active service fails,
103 * failover to standby may be done.
104 *
105 * @throws HealthCheckFailedException
106 * if the health check of a service fails.
107 * @throws AccessControlException
108 * if access is denied.
109 * @throws IOException
110 * if other errors happen
111 */
112 @Idempotent
113 public void monitorHealth() throws HealthCheckFailedException,
114 AccessControlException,
115 IOException;
116
117 /**
118 * Request service to transition to active state. No operation, if the
119 * service is already in active state.
120 *
121 * @throws ServiceFailedException
122 * if transition from standby to active fails.
123 * @throws AccessControlException
124 * if access is denied.
125 * @throws IOException
126 * if other errors happen
127 */
128 @Idempotent
129 public void transitionToActive(StateChangeRequestInfo reqInfo)
130 throws ServiceFailedException,
131 AccessControlException,
132 IOException;
133
134 /**
135 * Request service to transition to standby state. No operation, if the
136 * service is already in standby state.
137 *
138 * @throws ServiceFailedException
139 * if transition from active to standby fails.
140 * @throws AccessControlException
141 * if access is denied.
142 * @throws IOException
143 * if other errors happen
144 */
145 @Idempotent
146 public void transitionToStandby(StateChangeRequestInfo reqInfo)
147 throws ServiceFailedException,
148 AccessControlException,
149 IOException;
150
151 /**
152 * Return the current status of the service. The status indicates
153 * the current <em>state</em> (e.g ACTIVE/STANDBY) as well as
154 * some additional information. {@see HAServiceStatus}
155 *
156 * @throws AccessControlException
157 * if access is denied.
158 * @throws IOException
159 * if other errors happen
160 */
161 @Idempotent
162 public HAServiceStatus getServiceStatus() throws AccessControlException,
163 IOException;
164 }