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/*
 * 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
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 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
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package org.apache.brooklyn.api.mgmt.ha;

import java.util.Map;

import com.google.common.annotations.Beta;
import com.google.common.annotations.VisibleForTesting;

/**
 * Monitors other management nodes (via the {@link ManagementPlaneSyncRecordPersister}) to detect
 * if the current master has failed or stopped. If so, then deterministically chooses a new master.
 * If that master is self, then promotes.

 * Users are not expected to implement this class, or to call methods on it directly.
 * 
 * Expected lifecycle of methods calls on this is:
 * 
    *
  1. {@link #setPersister(ManagementPlaneSyncRecordPersister)} *
  2. Exactly one of {@link #disabled()} or {@link #start(HighAvailabilityMode)} *
  3. {@link #stop()} *
* * @since 0.7.0 */ @Beta public interface HighAvailabilityManager { ManagementNodeState getNodeState(); /** The time in milliseconds when the state was last changed. -1 if no state transition has occurred yet.*/ long getLastStateChange(); /** * @param persister * @return self */ HighAvailabilityManager setPersister(ManagementPlaneSyncRecordPersister persister); /** * Indicates that HA is disabled: this node will act as the only management node in this management plane, * and will not persist HA meta-information (meaning other nodes cannot join). *

* Subsequently can expect {@link #getNodeState()} to be {@link ManagementNodeState#MASTER} * and {@link #loadManagementPlaneSyncRecord(boolean)} to show just this one node -- * as if it were running HA with just one node -- * but {@link #isRunning()} will return false. *

* Currently this method is intended to be called early in the lifecycle, * instead of {@link #start(HighAvailabilityMode)}. It may be an error if * this is called after this HA Manager is started. */ @Beta void disabled(); /** Whether HA mode is operational */ boolean isRunning(); /** * Starts the monitoring of other nodes (and thus potential promotion of this node from standby to master). *

* When this method returns, the status of this node will be set, * either {@link ManagementNodeState#MASTER} if appropriate * or {@link ManagementNodeState#STANDBY} / {@link ManagementNodeState#HOT_STANDBY} / {@link ManagementNodeState#HOT_BACKUP}. * * @param startMode mode to start with * @throws IllegalStateException if current state of the management-plane doesn't match that desired by {@code startMode} */ void start(HighAvailabilityMode startMode); /** * Stops this node, then publishes own status (via {@link ManagementPlaneSyncRecordPersister} of {@link ManagementNodeState#TERMINATED}. */ void stop(); /** changes the mode that this HA server is running in *

* note it will be an error to {@link #changeMode(HighAvailabilityMode)} to {@link ManagementNodeState#MASTER} * when there is already a master; to promote a node explicitly set its priority higher than * the others and invoke {@link #changeMode(HighAvailabilityMode)} to a standby mode on the existing master */ void changeMode(HighAvailabilityMode mode); /** sets the priority, and publishes it synchronously so it is canonical */ void setPriority(long priority); long getPriority(); /** deletes non-master node records; active nodes (including this) will republish, * so this provides a simple way to clean out the cache of dead brooklyn nodes */ @Beta void publishClearNonMaster(); /** * Returns a snapshot of the management-plane's current / most-recently-known status, * as last read from {@link #loadManagementPlaneSyncRecord(boolean)}, or null if none read. */ ManagementPlaneSyncRecord getLastManagementPlaneSyncRecord(); /** * @param useLocalKnowledgeForThisNode - if true, the record for this mgmt node will be replaced with the * actual current status known in this JVM (may be more recent than what is persisted); * for most purposes there is little difference but in some cases the local node being updated * may be explicitly wanted or not wanted */ ManagementPlaneSyncRecord loadManagementPlaneSyncRecord(boolean useLocalKnowledgeForThisNode); @VisibleForTesting ManagementPlaneSyncRecordPersister getPersister(); /** Returns a collection of metrics */ Map getMetrics(); }





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