jiajunwang commented on a change in pull request #827: Add intermediate storage for customized state URL: https://github.com/apache/helix/pull/827#discussion_r387864354
########## File path: helix-core/src/main/java/org/apache/helix/common/caches/ParticipantStateCache.java ########## @@ -0,0 +1,183 @@ +package org.apache.helix.common.caches; + +/* + * 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. + */ + +import com.google.common.collect.Maps; +import java.util.ArrayList; +import java.util.Collections; +import java.util.HashMap; +import java.util.HashSet; +import java.util.List; +import java.util.Map; +import java.util.Set; +import org.apache.helix.HelixDataAccessor; +import org.apache.helix.PropertyKey; +import org.apache.helix.common.controllers.ControlContextProvider; +import org.apache.helix.controller.LogUtil; +import org.apache.helix.model.LiveInstance; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * Represent a cache that holds a certain participant side state of for the whole cluster. + */ +public abstract class ParticipantStateCache<T> extends AbstractDataCache { + private static Logger LOG = LoggerFactory.getLogger(ParticipantStateCache.class); + protected Map<String, Map<String, Map<String, T>>> _participantStateMap; + + protected Map<PropertyKey, T> _participantStateCache = Maps.newHashMap(); + + public ParticipantStateCache(ControlContextProvider controlContextProvider) { + super(controlContextProvider); + _participantStateMap = Collections.emptyMap(); + } + + /** + * This refreshes the participant state cache data by re-fetching the data from zookeeper in an + * efficient way + * @param accessor + * @param liveInstanceMap map of all liveInstances in cluster + * @return + */ + public boolean refresh(HelixDataAccessor accessor, Map<String, LiveInstance> liveInstanceMap, + Boolean snapshotEnabled, Set<String> restrictedKeys) { + long startTime = System.currentTimeMillis(); + + refreshParticipantStatesCacheFromZk(accessor, liveInstanceMap, snapshotEnabled, restrictedKeys); + Map<String, Map<String, Map<String, T>>> allParticipantStateMap = new HashMap<>(); + // There should be 4 levels of keys. The first one is the cluster name, the second one is the + // instance name, the third one is a customized key (could be session Id or customized state + // type), the fourth one is the resourceName + for (PropertyKey key : _participantStateCache.keySet()) { + T participantState = _participantStateCache.get(key); + String[] params = key.getParams(); + if (participantState != null && params.length >= 4) { + String instanceName = params[1]; + String customizedName = params[2]; + String resourceName = params[3]; + Map<String, Map<String, T>> instanceMap = allParticipantStateMap.get(instanceName); + if (instanceMap == null) { + instanceMap = Maps.newHashMap(); + allParticipantStateMap.put(instanceName, instanceMap); + } + Map<String, T> customizedMap = instanceMap.get(customizedName); + if (customizedMap == null) { + customizedMap = Maps.newHashMap(); + instanceMap.put(customizedName, customizedMap); + } + customizedMap.put(resourceName, participantState); + } else { + LogUtil.logError(LOG, genEventInfo(), + "Invalid key found in the participant state cache" + key); + } + } + + _participantStateMap = Collections.unmodifiableMap(allParticipantStateMap); + + long endTime = System.currentTimeMillis(); + LogUtil.logInfo(LOG, genEventInfo(), + "END: participantStateCache.refresh() for cluster " + + _controlContextProvider.getClusterName() + ", started at : " + startTime + ", took " + + (endTime - startTime) + " ms"); + if (LOG.isDebugEnabled()) { + LogUtil.logDebug(LOG, genEventInfo(), + String.format("Participant State refreshed : %s", _participantStateMap.toString())); + } + return true; + } + + // reload participant states that has been changed from zk to local cache. + private void refreshParticipantStatesCacheFromZk(HelixDataAccessor accessor, + Map<String, LiveInstance> liveInstanceMap, Boolean snapshotEnabled, + Set<String> restrictedKeys) { + + long start = System.currentTimeMillis(); + Set<PropertyKey> participantStateKeys = new HashSet<>(); + PopulateParticipantKeys(accessor, participantStateKeys, liveInstanceMap, restrictedKeys); + + // All new entries from zk not cached locally yet should be read from ZK. + Set<PropertyKey> reloadKeys = new HashSet<>(participantStateKeys); + reloadKeys.removeAll(_participantStateCache.keySet()); + + Set<PropertyKey> cachedKeys = new HashSet<>(_participantStateCache.keySet()); + cachedKeys.retainAll(participantStateKeys); + + Set<PropertyKey> reloadedKeys = new HashSet<>(); + Map<PropertyKey, T> newStateCache = Collections.unmodifiableMap(refreshProperties(accessor, + reloadKeys, new ArrayList<>(cachedKeys), _participantStateCache, reloadedKeys)); + + if (snapshotEnabled) { + refreshSnapshot(newStateCache, _participantStateCache, reloadedKeys); + } + + _participantStateCache = newStateCache; + + if (LOG.isDebugEnabled()) { + LogUtil.logDebug(LOG, genEventInfo(), "# of participant state reload: " + reloadKeys.size() + + ", skipped:" + (participantStateKeys.size() - reloadKeys.size()) + ". took " + + (System.currentTimeMillis() - start) + + " ms to reload new participant states for cluster: " + + _controlContextProvider.getClusterName() + "and state: " + this.getClass().getName()); + } + } + + public void PopulateParticipantKeys(HelixDataAccessor accessor, Review comment: Usually, this class should be protected only. 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