NealSun96 commented on a change in pull request #727: Add MetadataStoreRoutingDataWriter with DistributedLeaderElection URL: https://github.com/apache/helix/pull/727#discussion_r376675370
########## File path: helix-rest/src/main/java/org/apache/helix/rest/metadatastore/accessor/ZkRoutingDataWriter.java ########## @@ -0,0 +1,256 @@ +package org.apache.helix.rest.metadatastore.accessor; + +/* + * 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 java.util.Collections; +import java.util.List; +import java.util.Map; + +import org.I0Itec.zkclient.exception.ZkNodeExistsException; +import org.apache.helix.ZNRecord; +import org.apache.helix.manager.zk.ZNRecordSerializer; +import org.apache.helix.manager.zk.ZkBaseDataAccessor; +import org.apache.helix.manager.zk.client.DedicatedZkClientFactory; +import org.apache.helix.manager.zk.client.HelixZkClient; +import org.apache.helix.rest.metadatastore.concurrency.ZkDistributedLeaderElection; +import org.apache.helix.rest.metadatastore.constant.MetadataStoreRoutingConstants; +import org.apache.helix.rest.metadatastore.exceptions.ZkLockException; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + + +public class ZkRoutingDataWriter implements MetadataStoreRoutingDataWriter { + private static final Logger LOG = LoggerFactory.getLogger(ZkBaseDataAccessor.class); + + private final String _namespace; + private final String _zkAddress; + private final HelixZkClient _zkClient; + private final ZkDistributedLeaderElection _leaderElection; + + public ZkRoutingDataWriter(String namespace, String zkAddress) { + if (namespace == null || namespace.isEmpty()) { + throw new IllegalArgumentException("namespace cannot be null or empty!"); + } + _namespace = namespace; + if (zkAddress == null || zkAddress.isEmpty()) { + throw new IllegalArgumentException("Zk address cannot be null or empty!"); + } + _zkAddress = zkAddress; + _zkClient = DedicatedZkClientFactory.getInstance() + .buildZkClient(new HelixZkClient.ZkConnectionConfig(zkAddress), + new HelixZkClient.ZkClientConfig().setZkSerializer(new ZNRecordSerializer())); + + // Ensure that ROUTING_DATA_PATH exists in ZK. If not, create + // create() semantic will fail if it already exists + try { + _zkClient.createPersistent(MetadataStoreRoutingConstants.ROUTING_DATA_PATH); + } catch (ZkNodeExistsException e) { + // This is okay + } + + // Get the hostname (REST endpoint) from System property + ZNRecord myServerInfo = new ZNRecord("dummy hostname"); + _leaderElection = new ZkDistributedLeaderElection(_zkClient, + MetadataStoreRoutingConstants.LEADER_ELECTION_ZNODE, myServerInfo); + } + + @Override + public synchronized boolean addMetadataStoreRealm(String realm) { + if (_leaderElection.isLeader()) { + if (_zkClient.isClosed()) { + throw new IllegalStateException("ZkClient is closed!"); + } + return createZkRealm(realm); + } + + // TODO: Forward the request to leader + return true; + } + + @Override + public synchronized boolean deleteMetadataStoreRealm(String realm) { + if (_leaderElection.isLeader()) { + if (_zkClient.isClosed()) { + throw new IllegalStateException("ZkClient is closed!"); + } + return _zkClient.delete(MetadataStoreRoutingConstants.ROUTING_DATA_PATH + "/" + realm); + } + + // TODO: Forward the request to leader + return true; + } + + @Override + public synchronized boolean addShardingKey(String realm, String shardingKey) { + if (_leaderElection.isLeader()) { + if (_zkClient.isClosed()) { + throw new IllegalStateException("ZkClient is closed!"); + } + // If the realm does not exist already, then create the realm + if (!_zkClient.exists(MetadataStoreRoutingConstants.ROUTING_DATA_PATH + "/" + realm)) { + // Create the realm + if (!createZkRealm(realm)) { + // Failed to create the realm - log and return false + LOG.error( + "Failed to add sharding key because ZkRealm creation failed! Namespace: {}, Realm: {}, Sharding key: {}", + _namespace, realm, shardingKey); + return false; + } + } + + // Add the sharding key to an empty ZNRecord + ZNRecord znRecord; + try { + znRecord = + _zkClient.readData(MetadataStoreRoutingConstants.ROUTING_DATA_PATH + "/" + realm); + } catch (Exception e) { + LOG.error( + "Failed to read the realm ZNRecord in addShardingKey()! Namespace: {}, Realm: {}, ShardingKey: {}", + _namespace, realm, shardingKey, e); + return false; + } + znRecord.setListField(MetadataStoreRoutingConstants.ZNRECORD_LIST_FIELD_KEY, + Collections.singletonList(shardingKey)); + try { + _zkClient + .writeData(MetadataStoreRoutingConstants.ROUTING_DATA_PATH + "/" + realm, znRecord); + } catch (Exception e) { + LOG.error( + "Failed to write the realm ZNRecord in addShardingKey()! Namespace: {}, Realm: {}, ShardingKey: {}", + _namespace, realm, shardingKey, e); + return false; + } + return true; + } + + // TODO: Forward the request to leader + return true; + } + + @Override + public synchronized boolean deleteShardingKey(String realm, String shardingKey) { + if (_leaderElection.isLeader()) { + if (_zkClient.isClosed()) { + throw new IllegalStateException("ZkClient is closed!"); + } + ZNRecord znRecord = + _zkClient.readData(MetadataStoreRoutingConstants.ROUTING_DATA_PATH + "/" + realm, true); + if (znRecord == null || !znRecord + .getListField(MetadataStoreRoutingConstants.ZNRECORD_LIST_FIELD_KEY) + .contains(shardingKey)) { + // This realm does not exist or shardingKey doesn't exist. Return true! + return true; + } + znRecord.getListField(MetadataStoreRoutingConstants.ZNRECORD_LIST_FIELD_KEY) + .remove(shardingKey); + // Overwrite this ZNRecord with the sharding key removed + try { + _zkClient + .writeData(MetadataStoreRoutingConstants.ROUTING_DATA_PATH + "/" + realm, znRecord); + } catch (Exception e) { + LOG.error( + "Failed to write the data back in deleteShardingKey()! Namespace: {}, Realm: {}, ShardingKey: {}", + _namespace, realm, shardingKey, e); + return false; + } + return true; + } + + // TODO: Forward the request to leader + return true; + } + + @Override + public synchronized boolean setRoutingData(Map<String, List<String>> routingData) { + if (_leaderElection.isLeader()) { + if (_zkClient.isClosed()) { + throw new IllegalStateException("ZkClient is closed!"); + } + if (routingData == null) { + throw new IllegalArgumentException("routingData given is null!"); + } + + // Remove existing routing data + for (String zkRealm : _zkClient + .getChildren(MetadataStoreRoutingConstants.ROUTING_DATA_PATH)) { + if (!_zkClient.delete(MetadataStoreRoutingConstants.ROUTING_DATA_PATH + "/" + zkRealm)) { + LOG.error( + "Failed to delete existing routing data in setRoutingData()! Namespace: {}, Realm: {}", + _namespace, zkRealm); + return false; + } + } + + // For each ZkRealm, write the given routing data to ZooKeeper + for (Map.Entry<String, List<String>> routingDataEntry : routingData.entrySet()) { + String zkRealm = routingDataEntry.getKey(); + List<String> shardingKeyList = routingDataEntry.getValue(); + + ZNRecord znRecord = new ZNRecord(zkRealm); + znRecord + .setListField(MetadataStoreRoutingConstants.ZNRECORD_LIST_FIELD_KEY, shardingKeyList); + try { + if (!_zkClient.exists(MetadataStoreRoutingConstants.ROUTING_DATA_PATH + "/" + zkRealm)) { Review comment: I believe @narendly 's logic here is to not write on top of an existing node, therefore the if statement is necessary even with try catch. However, this check is unnecessary for another reason: this is a synchronized function and each loop of `routingData` guarantees a different `zkRealm`, therefore the node will never already exist here. Correct me if I'm wrong, please. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
