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From: aledsage <git@git.apache.org>
To: dev@brooklyn.incubator.apache.org
Reply-To: dev@brooklyn.incubator.apache.org
References: <git-pr-272-incubator-brooklyn@git.apache.org>
In-Reply-To: <git-pr-272-incubator-brooklyn@git.apache.org>
Subject: [GitHub] incubator-brooklyn pull request: Brooklyn node and cluster
 upgrade
Content-Type: text/plain
Message-Id: <20141027182956.77A7690ABD2@tyr.zones.apache.org>
Date: Mon, 27 Oct 2014 18:29:56 +0000 (UTC)

Github user aledsage commented on a diff in the pull request:

    https://github.com/apache/incubator-brooklyn/pull/272#discussion_r19426439
  
    --- Diff: software/base/src/main/java/brooklyn/entity/brooklynnode/effector/SelectMasterEffectorBody.java ---
    @@ -0,0 +1,173 @@
    +/*
    + * 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 brooklyn.entity.brooklynnode.effector;
    +
    +import java.util.NoSuchElementException;
    +import java.util.concurrent.Callable;
    +import java.util.concurrent.atomic.AtomicBoolean;
    +
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +import brooklyn.entity.Effector;
    +import brooklyn.entity.Entity;
    +import brooklyn.entity.Group;
    +import brooklyn.entity.basic.EntityPredicates;
    +import brooklyn.entity.brooklynnode.BrooklynCluster;
    +import brooklyn.entity.brooklynnode.BrooklynCluster.SelectMasterEffector;
    +import brooklyn.entity.brooklynnode.BrooklynNode;
    +import brooklyn.entity.brooklynnode.BrooklynNode.SetHighAvailabilityModeEffector;
    +import brooklyn.entity.brooklynnode.BrooklynNode.SetHighAvailabilityPriorityEffector;
    +import brooklyn.entity.effector.EffectorBody;
    +import brooklyn.entity.effector.Effectors;
    +import brooklyn.management.ha.HighAvailabilityMode;
    +import brooklyn.management.ha.ManagementNodeState;
    +import brooklyn.util.collections.MutableMap;
    +import brooklyn.util.config.ConfigBag;
    +import brooklyn.util.repeat.Repeater;
    +import brooklyn.util.task.DynamicTasks;
    +import brooklyn.util.time.Duration;
    +
    +import com.google.api.client.util.Preconditions;
    +import com.google.common.collect.Iterables;
    +
    +public class SelectMasterEffectorBody extends EffectorBody<Void> implements SelectMasterEffector {
    +    public static final Effector<Void> SELECT_MASTER = Effectors.effector(SelectMasterEffector.SELECT_MASTER).impl(new SelectMasterEffectorBody()).build();
    +    
    +    private static final Logger LOG = LoggerFactory.getLogger(SelectMasterEffectorBody.class);
    +
    +    private static final int HA_STANDBY_PRIORITY = 0;
    +    private static final int HA_MASTER_PRIORITY = 1;
    +
    +    private AtomicBoolean selectMasterInProgress = new AtomicBoolean();
    +
    +    @Override
    +    public Void call(ConfigBag parameters) {
    +        if (!selectMasterInProgress.compareAndSet(false, true)) {
    +            throw new IllegalStateException("A master change is already in progress.");
    +        }
    +
    +        try {
    +            selectMaster(parameters);
    +        } finally {
    +            selectMasterInProgress.set(false);
    +        }
    +        return null;
    +    }
    +
    +    private void selectMaster(ConfigBag parameters) {
    +        String newMasterId = parameters.get(NEW_MASTER_ID);
    +        Preconditions.checkNotNull(newMasterId, NEW_MASTER_ID.getName() + " parameter is required");
    +
    +        final Entity oldMaster = entity().getAttribute(BrooklynCluster.MASTER_NODE);
    +        if (oldMaster != null && oldMaster.getId().equals(newMasterId)) {
    +            LOG.info(newMasterId + " is already the current master, no change needed.");
    +            return;
    +        }
    +
    +        final Entity newMaster = getMember(newMasterId);
    +
    +        //1. Increase the priority of the node we wish to become master
    +        setNodePriority(newMaster, HA_MASTER_PRIORITY);
    +
    +        //2. Denote the existing master so a new election takes place
    +        try {
    +            //If no master was yet selected, at least wait to see
    +            //if the new master will be what we expect.
    +            if (oldMaster != null) {
    +                setNodeState(oldMaster, HighAvailabilityMode.HOT_STANDBY);
    +            }
    +
    +            waitMasterHandover(oldMaster, newMaster);
    +        } finally {
    +            //3. Revert the priority of the node once it has become master
    +            setNodePriority(newMaster, HA_STANDBY_PRIORITY);
    +        }
    +
    +        checkMasterSelected(newMaster);
    +    }
    +
    +    private void waitMasterHandover(final Entity oldMaster, final Entity newMaster) {
    +        boolean masterChanged = Repeater.create()
    +            .backoff(Duration.millis(500), 1.2, Duration.FIVE_SECONDS)
    +            .limitTimeTo(Duration.ONE_MINUTE)
    +            .until(new Callable<Boolean>() {
    +                @Override
    +                public Boolean call() throws Exception {
    +                    Entity master = getMasterNode();
    +                    return master != oldMaster && master != null;
    +                }
    +            })
    +            .run();
    +        if (!masterChanged) {
    +            LOG.warn("Timeout waiting for node to become master: " + newMaster + ".");
    +        }
    +    }
    +
    +    private void setNodeState(Entity oldMaster, HighAvailabilityMode mode) {
    +        ManagementNodeState oldState = DynamicTasks.queue(
    +                Effectors.invocation(
    +                        oldMaster,
    +                        BrooklynNode.SET_HIGH_AVAILABILITY_MODE,
    +                        MutableMap.of(SetHighAvailabilityModeEffector.MODE, mode))
    +            ).asTask().getUnchecked();
    +
    +        if (oldState != ManagementNodeState.MASTER) {
    +            LOG.warn("The previous HA state on node " + oldMaster.getId() + " was " + oldState +
    +                    ", while the expected value is " + ManagementNodeState.MASTER + ".");
    +        }
    +    }
    +
    +    private void setNodePriority(Entity newMaster, int newPriority) {
    +        Integer oldPriority = DynamicTasks.queue(
    +                Effectors.invocation(
    +                    newMaster,
    +                    BrooklynNode.SET_HIGH_AVAILABILITY_PRIORITY,
    +                    MutableMap.of(SetHighAvailabilityPriorityEffector.PRIORITY, newPriority))
    +            ).asTask().getUnchecked();
    +
    +        Integer expectedPriority = (newPriority == HA_MASTER_PRIORITY ? HA_STANDBY_PRIORITY : HA_MASTER_PRIORITY);
    --- End diff --
    
    Again this logic is surprising given the method name.
    Also, the parameter name `newMaster` doesn't feel right, given we're either setting it to be master or standby.


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