HoustonPutman commented on code in PR #1650: URL: https://github.com/apache/solr/pull/1650#discussion_r1224420594
########## solr/core/src/java/org/apache/solr/cloud/api/collections/ReplicaMigrationUtils.java: ########## @@ -0,0 +1,304 @@ +/* + * 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.solr.cloud.api.collections; + +import static org.apache.solr.common.params.CommonAdminParams.ASYNC; + +import java.io.IOException; +import java.lang.invoke.MethodHandles; +import java.util.ArrayList; +import java.util.Collection; +import java.util.Collections; +import java.util.HashMap; +import java.util.List; +import java.util.Locale; +import java.util.Map; +import java.util.concurrent.CountDownLatch; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicBoolean; +import org.apache.solr.cloud.ActiveReplicaWatcher; +import org.apache.solr.common.SolrCloseableLatch; +import org.apache.solr.common.cloud.ClusterState; +import org.apache.solr.common.cloud.CollectionStateWatcher; +import org.apache.solr.common.cloud.Replica; +import org.apache.solr.common.cloud.ZkNodeProps; +import org.apache.solr.common.cloud.ZkStateReader; +import org.apache.solr.common.params.CoreAdminParams; +import org.apache.solr.common.util.NamedList; +import org.apache.zookeeper.KeeperException; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +public class ReplicaMigrationUtils { + private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass()); + + /** + * Code to migrate replicas to already chosen nodes. This will create new replicas, and delete the + * old replicas after the creation is done. + * + * <p>If an error occurs during the creation of new replicas, all new replicas will be deleted. + * + * @param ccc The collection command context to use from the API that calls this method + * @param movements a map from replica to the new node that the replica should live on + * @param parallel whether the replica creations should be done in parallel + * @param waitForFinalState wait for the final state of all newly created replicas before + * continuing + * @param timeout the amount of time to wait for new replicas to be created + * @param asyncId If provided, the command will be run under the given asyncId + * @param results push results (successful and failure) onto this list + * @return whether the command was successful + */ + static boolean migrateReplicas( + CollectionCommandContext ccc, + Map<Replica, String> movements, + boolean parallel, + boolean waitForFinalState, + int timeout, + String asyncId, + NamedList<Object> results) + throws IOException, InterruptedException, KeeperException { + // how many leaders are we moving? for these replicas we have to make sure that either: + // * another existing replica can become a leader, or + // * we wait until the newly created replica completes recovery (and can become the new leader) + // If waitForFinalState=true we wait for all replicas + int numLeaders = 0; + for (Replica replica : movements.keySet()) { + if (replica.isLeader() || waitForFinalState) { + numLeaders++; + } + } + // map of collectionName_coreNodeName to watchers + Map<String, CollectionStateWatcher> watchers = new HashMap<>(); + List<ZkNodeProps> createdReplicas = new ArrayList<>(); + + AtomicBoolean anyOneFailed = new AtomicBoolean(false); + SolrCloseableLatch countDownLatch = + new SolrCloseableLatch(movements.size(), ccc.getCloseableToLatchOn()); + + SolrCloseableLatch replicasToRecover = + new SolrCloseableLatch(numLeaders, ccc.getCloseableToLatchOn()); + + ClusterState clusterState = ccc.getZkStateReader().getClusterState(); + + for (Map.Entry<Replica, String> movement : movements.entrySet()) { + Replica sourceReplica = movement.getKey(); + String targetNode = movement.getValue(); + String sourceCollection = sourceReplica.getCollection(); + if (log.isInfoEnabled()) { + log.info( + "Going to create replica for collection={} shard={} on node={}", + sourceCollection, + sourceReplica.getShard(), + targetNode); + } + + ZkNodeProps msg = + sourceReplica + .toFullProps() + .plus("parallel", String.valueOf(parallel)) + .plus(CoreAdminParams.NODE, targetNode); + if (asyncId != null) msg.getProperties().put(ASYNC, asyncId); + NamedList<Object> nl = new NamedList<>(); + final ZkNodeProps addedReplica = + new AddReplicaCmd(ccc) + .addReplica( + clusterState, + msg, + nl, + () -> { + countDownLatch.countDown(); + if (nl.get("failure") != null) { + String errorString = + String.format( + Locale.ROOT, + "Failed to create replica for collection=%s shard=%s" + " on node=%s", + sourceCollection, + sourceReplica.getShard(), + targetNode); + log.warn(errorString); + // one replica creation failed. Make the best attempt to + // delete all the replicas created so far in the target + // and exit + synchronized (results) { + results.add("failure", errorString); + anyOneFailed.set(true); + } + } else { + if (log.isDebugEnabled()) { + log.debug( + "Successfully created replica for collection={} shard={} on node={}", + sourceCollection, + sourceReplica.getShard(), + targetNode); + } + } + }) + .get(0); + + if (addedReplica != null) { + createdReplicas.add(addedReplica); + if (sourceReplica.isLeader() || waitForFinalState) { + String shardName = sourceReplica.getShard(); + String replicaName = sourceReplica.getName(); + String key = sourceCollection + "_" + replicaName; + CollectionStateWatcher watcher; + if (waitForFinalState) { + watcher = + new ActiveReplicaWatcher( + sourceCollection, + null, + Collections.singletonList(addedReplica.getStr(ZkStateReader.CORE_NAME_PROP)), + replicasToRecover); + } else { + watcher = + new LeaderRecoveryWatcher( + sourceCollection, + shardName, + replicaName, + addedReplica.getStr(ZkStateReader.CORE_NAME_PROP), + replicasToRecover); + } + watchers.put(key, watcher); + log.debug("--- adding {}, {}", key, watcher); + ccc.getZkStateReader().registerCollectionStateWatcher(sourceCollection, watcher); + } else { + log.debug("--- not waiting for {}", addedReplica); + } + } + } + + log.debug("Waiting for replicas to be added"); + if (!countDownLatch.await(timeout, TimeUnit.SECONDS)) { + log.info("Timed out waiting for replicas to be added"); + anyOneFailed.set(true); + } else { + log.debug("Finished waiting for replicas to be added"); + } + + // now wait for leader replicas to recover + log.debug("Waiting for {} leader replicas to recover", numLeaders); + if (!replicasToRecover.await(timeout, TimeUnit.SECONDS)) { Review Comment: We really only need to ensure that there is another active replica to take leadership if we are deleting a leader in `cleanupReplicas()`, so we should probably just create another latch and loop for it after the `countDownLatch` is complete. 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