Java tutorial
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See the License for the * specific language governing permissions and limitations * under the License. */ package org.apache.brooklyn.entity.brooklynnode.effector; import java.util.NoSuchElementException; import java.util.concurrent.Callable; import java.util.concurrent.atomic.AtomicBoolean; import org.apache.brooklyn.api.effector.Effector; import org.apache.brooklyn.api.entity.Entity; import org.apache.brooklyn.api.entity.Group; import org.apache.brooklyn.api.mgmt.ha.HighAvailabilityMode; import org.apache.brooklyn.api.mgmt.ha.ManagementNodeState; import org.apache.brooklyn.core.effector.EffectorBody; import org.apache.brooklyn.core.effector.Effectors; import org.apache.brooklyn.core.entity.EntityPredicates; import org.apache.brooklyn.entity.brooklynnode.BrooklynCluster; import org.apache.brooklyn.entity.brooklynnode.BrooklynNode; import org.apache.brooklyn.entity.brooklynnode.BrooklynCluster.SelectMasterEffector; import org.apache.brooklyn.entity.brooklynnode.BrooklynNode.SetHighAvailabilityModeEffector; import org.apache.brooklyn.entity.brooklynnode.BrooklynNode.SetHighAvailabilityPriorityEffector; import org.apache.brooklyn.util.collections.MutableMap; import org.apache.brooklyn.util.core.config.ConfigBag; import org.apache.brooklyn.util.core.task.DynamicTasks; import org.apache.brooklyn.util.repeat.Repeater; import org.apache.brooklyn.util.time.Duration; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.google.common.base.Preconditions; import com.google.common.base.Objects; 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 toggleNodePriority(newMaster, HA_MASTER_PRIORITY); //2. Demote the existing master so a new election takes place try { // this allows the finally block to run even on failure DynamicTasks.swallowChildrenFailures(); if (oldMaster != null) { demoteOldMaster(oldMaster, HighAvailabilityMode.HOT_STANDBY); } waitMasterHandover(oldMaster, newMaster); } finally { //3. Revert the priority of the node once it has become master toggleNodePriority(newMaster, HA_STANDBY_PRIORITY); } checkMasterSelected(newMaster); } private void waitMasterHandover(final Entity oldMaster, final Entity newMaster) { boolean masterChanged = Repeater.create() .backoff(Repeater.DEFAULT_REAL_QUICK_PERIOD, 1.5, Duration.FIVE_SECONDS) .limitTimeTo(Duration.ONE_MINUTE).until(new Callable<Boolean>() { @Override public Boolean call() throws Exception { Entity master = getMasterNode(); return !Objects.equal(master, oldMaster) && master != null; } }).run(); if (!masterChanged) { LOG.warn("Timeout waiting for node to become master: " + newMaster + "."); } } private void demoteOldMaster(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 toggleNodePriority(Entity node, int newPriority) { Integer oldPriority = DynamicTasks .queue(Effectors.invocation(node, BrooklynNode.SET_HIGH_AVAILABILITY_PRIORITY, MutableMap.of(SetHighAvailabilityPriorityEffector.PRIORITY, newPriority))) .asTask().getUnchecked(); Integer expectedPriority = (newPriority == HA_MASTER_PRIORITY ? HA_STANDBY_PRIORITY : HA_MASTER_PRIORITY); if (oldPriority != expectedPriority) { LOG.warn("The previous HA priority on node " + node.getId() + " was " + oldPriority + ", while the expected value is " + expectedPriority + " (while setting priority " + newPriority + ")."); } } private void checkMasterSelected(Entity newMaster) { Entity actualMaster = getMasterNode(); if (actualMaster != newMaster) { throw new IllegalStateException("Expected node " + newMaster + " to be master, but found that " + "master is " + actualMaster + " instead."); } } private Entity getMember(String memberId) { Group cluster = (Group) entity(); try { return Iterables.find(cluster.getMembers(), EntityPredicates.idEqualTo(memberId)); } catch (NoSuchElementException e) { throw new IllegalStateException(memberId + " is not an ID of brooklyn node in this cluster"); } } private Entity getMasterNode() { return entity().getAttribute(BrooklynCluster.MASTER_NODE); } }