org.apache.hadoop.ha.HAServiceProtocol Maven / Gradle / Ivy
/**
* 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.ha;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.CommonConfigurationKeys;
import org.apache.hadoop.io.retry.Idempotent;
import org.apache.hadoop.security.AccessControlException;
import org.apache.hadoop.security.KerberosInfo;
import java.io.IOException;
/**
* Protocol interface that provides High Availability related primitives to
* monitor and fail-over the service.
*
* This interface could be used by HA frameworks to manage the service.
*/
@KerberosInfo(
serverPrincipal=CommonConfigurationKeys.HADOOP_SECURITY_SERVICE_USER_NAME_KEY)
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface HAServiceProtocol {
/**
* Initial version of the protocol
*/
public static final long versionID = 1L;
/**
* An HA service may be in active or standby state. During startup, it is in
* an unknown INITIALIZING state. During shutdown, it is in the STOPPING state
* and can no longer return to active/standby states.
*/
public enum HAServiceState {
INITIALIZING("initializing"),
ACTIVE("active"),
STANDBY("standby"),
OBSERVER("observer"),
STOPPING("stopping");
private String name;
HAServiceState(String name) {
this.name = name;
}
@Override
public String toString() {
return name;
}
}
public enum RequestSource {
REQUEST_BY_USER,
REQUEST_BY_USER_FORCED,
REQUEST_BY_ZKFC;
}
/**
* Information describing the source for a request to change state.
* This is used to differentiate requests from automatic vs CLI
* failover controllers, and in the future may include epoch
* information.
*/
public static class StateChangeRequestInfo {
private final RequestSource source;
public StateChangeRequestInfo(RequestSource source) {
super();
this.source = source;
}
public RequestSource getSource() {
return source;
}
}
/**
* Monitor the health of service. This periodically called by the HA
* frameworks to monitor the health of the service.
*
* Service is expected to perform checks to ensure it is functional.
* If the service is not healthy due to failure or partial failure,
* it is expected to throw {@link HealthCheckFailedException}.
* The definition of service not healthy is left to the service.
*
* Note that when health check of an Active service fails,
* failover to standby may be done.
*
* @throws HealthCheckFailedException
* if the health check of a service fails.
* @throws AccessControlException
* if access is denied.
* @throws IOException
* if other errors happen
*/
@Idempotent
public void monitorHealth() throws HealthCheckFailedException,
AccessControlException,
IOException;
/**
* Request service to transition to active state. No operation, if the
* service is already in active state.
*
* @throws ServiceFailedException
* if transition from standby to active fails.
* @throws AccessControlException
* if access is denied.
* @throws IOException
* if other errors happen
*/
@Idempotent
public void transitionToActive(StateChangeRequestInfo reqInfo)
throws ServiceFailedException,
AccessControlException,
IOException;
/**
* Request service to transition to standby state. No operation, if the
* service is already in standby state.
*
* @throws ServiceFailedException
* if transition from active to standby fails.
* @throws AccessControlException
* if access is denied.
* @throws IOException
* if other errors happen
*/
@Idempotent
public void transitionToStandby(StateChangeRequestInfo reqInfo)
throws ServiceFailedException,
AccessControlException,
IOException;
/**
* Request service to transition to observer state. No operation, if the
* service is already in observer state.
*
* @throws ServiceFailedException
* if transition from standby to observer fails.
* @throws AccessControlException
* if access is denied.
* @throws IOException
* if other errors happen
*/
@Idempotent
void transitionToObserver(StateChangeRequestInfo reqInfo)
throws ServiceFailedException,
AccessControlException,
IOException;
/**
* Return the current status of the service. The status indicates
* the current state (e.g ACTIVE/STANDBY) as well as
* some additional information.
*
* @throws AccessControlException
* if access is denied.
* @throws IOException
* if other errors happen
* @see HAServiceStatus
*/
@Idempotent
public HAServiceStatus getServiceStatus() throws AccessControlException,
IOException;
}