| /* |
| * 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.iotdb.db.storageengine.dataregion.wal.allocation; |
| |
| import org.apache.iotdb.db.storageengine.dataregion.wal.node.IWALNode; |
| import org.apache.iotdb.db.storageengine.dataregion.wal.node.WALNode; |
| |
| import java.util.ArrayList; |
| import java.util.HashMap; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.concurrent.locks.Lock; |
| import java.util.concurrent.locks.ReentrantLock; |
| |
| /** |
| * This strategy creates wal nodes according to the number of memTables. Each wal node manages fixed |
| * number of memTables. |
| */ |
| public class ElasticStrategy extends AbstractNodeAllocationStrategy { |
| // each wal node manages fixed number of memTables |
| public static final int APPLICATION_NODE_RATIO = 4; |
| |
| // protect concurrent safety of wal nodes, including walNodes, nodeCursor and nodeIdCounter |
| private final Lock nodesLock = new ReentrantLock(); |
| // region these variables should be protected by nodesLock |
| // wal nodes, the max number of wal nodes is MAX_WAL_NUM |
| private final List<WALNode> walNodes; |
| // help allocate node for users |
| private final Map<String, WALNode> uniqueId2Nodes = new HashMap<>(); |
| // each wal node has a unique long value identifier |
| private int nodeIdCounter = -1; |
| |
| // endregion |
| |
| public ElasticStrategy() { |
| this.walNodes = new ArrayList<>(); |
| } |
| |
| // it's safe to not close WALNode here, we use clear method to close all WALNodes. |
| @SuppressWarnings("squid:S2095") |
| @Override |
| public IWALNode applyForWALNode(String applicantUniqueId) { |
| nodesLock.lock(); |
| try { |
| if (!uniqueId2Nodes.containsKey(applicantUniqueId)) { |
| // add 1 node when reaching threshold |
| if (uniqueId2Nodes.size() == walNodes.size() * APPLICATION_NODE_RATIO) { |
| nodeIdCounter++; |
| IWALNode node = createWALNode(String.valueOf(nodeIdCounter)); |
| if (!(node instanceof WALNode)) { |
| return node; |
| } |
| walNodes.add((WALNode) node); |
| } |
| uniqueId2Nodes.put(applicantUniqueId, walNodes.get(nodeIdCounter)); |
| } |
| |
| return uniqueId2Nodes.get(applicantUniqueId); |
| } finally { |
| nodesLock.unlock(); |
| } |
| } |
| |
| @Override |
| public List<WALNode> getNodesSnapshot() { |
| List<WALNode> snapshot; |
| nodesLock.lock(); |
| try { |
| snapshot = new ArrayList<>(walNodes); |
| } finally { |
| nodesLock.unlock(); |
| } |
| return snapshot; |
| } |
| |
| @Override |
| public int getNodesNum() { |
| return walNodes.size(); |
| } |
| |
| @Override |
| public void clear() { |
| nodesLock.lock(); |
| try { |
| nodeIdCounter = -1; |
| uniqueId2Nodes.clear(); |
| for (WALNode walNode : walNodes) { |
| walNode.close(); |
| } |
| walNodes.clear(); |
| } finally { |
| nodesLock.unlock(); |
| } |
| } |
| } |