| /** |
| * 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 exposed by the ZKFailoverController, allowing for graceful |
| * failover. |
| */ |
| @KerberosInfo( |
| serverPrincipal=CommonConfigurationKeys.HADOOP_SECURITY_SERVICE_USER_NAME_KEY) |
| @InterfaceAudience.Private |
| @InterfaceStability.Evolving |
| public interface ZKFCProtocol { |
| /** |
| * Initial version of the protocol |
| */ |
| public static final long versionID = 1L; |
| |
| /** |
| * Request that this service yield from the active node election for the |
| * specified time period. |
| * |
| * If the node is not currently active, it simply prevents any attempts |
| * to become active for the specified time period. Otherwise, it first |
| * tries to transition the local service to standby state, and then quits |
| * the election. |
| * |
| * If the attempt to transition to standby succeeds, then the ZKFC receiving |
| * this RPC will delete its own breadcrumb node in ZooKeeper. Thus, the |
| * next node to become active will not run any fencing process. Otherwise, |
| * the breadcrumb will be left, such that the next active will fence this |
| * node. |
| * |
| * After the specified time period elapses, the node will attempt to re-join |
| * the election, provided that its service is healthy. |
| * |
| * If the node has previously been instructed to cede active, and is still |
| * within the specified time period, the later command's time period will |
| * take precedence, resetting the timer. |
| * |
| * A call to cedeActive which specifies a 0 or negative time period will |
| * allow the target node to immediately rejoin the election, so long as |
| * it is healthy. |
| * |
| * @param millisToCede period for which the node should not attempt to |
| * become active |
| * @throws IOException if the operation fails |
| * @throws AccessControlException if the operation is disallowed |
| */ |
| @Idempotent |
| public void cedeActive(int millisToCede) |
| throws IOException, AccessControlException; |
| |
| /** |
| * Request that this node try to become active through a graceful failover. |
| * |
| * If the node is already active, this is a no-op and simply returns success |
| * without taking any further action. |
| * |
| * If the node is not healthy, it will throw an exception indicating that it |
| * is not able to become active. |
| * |
| * If the node is healthy and not active, it will try to initiate a graceful |
| * failover to become active, returning only when it has successfully become |
| * active. See {@link ZKFailoverController#gracefulFailoverToYou()} for the |
| * implementation details. |
| * |
| * If the node fails to successfully coordinate the failover, throws an |
| * exception indicating the reason for failure. |
| * |
| * @throws IOException if graceful failover fails |
| * @throws AccessControlException if the operation is disallowed |
| */ |
| @Idempotent |
| public void gracefulFailover() |
| throws IOException, AccessControlException; |
| } |