All Downloads are FREE. Search and download functionalities are using the official Maven repository.

com.splout.db.qnode.ReplicaBalancer Maven / Gradle / Ivy

Go to download

Splout SQL is a read only, horizontally scalable and partitioned SQL database that plays well with Hadoop.

The newest version!
package com.splout.db.qnode;

/*
 * #%L
 * Splout SQL Server
 * %%
 * Copyright (C) 2012 - 2013 Datasalt Systems S.L.
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see .
 * #L%
 */

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.splout.db.common.ReplicationEntry;
import com.splout.db.common.ReplicationMap;
import com.splout.db.common.Tablespace;
import com.splout.db.hazelcast.DNodeInfo;
import com.splout.db.hazelcast.TablespaceVersion;

/**
 * A specialized {@link QNode} module that takes care of detecting under-replicated replicas and possibly coordinating
 * sending files between DNodes to compensate those.
 * 

* TODO Work in progress: coordinating with Hazelcast, etc. Time to wait before sending an order-> SAFE MODE (QNode), * should not start this daemon before X time. */ public class ReplicaBalancer { protected final static Log log = LogFactory.getLog(ReplicaBalancer.class); private QNodeHandlerContext context; public ReplicaBalancer(QNodeHandlerContext context) { this.context = context; } /** * Bean that represents an action that has to be taken for balancing a partition. The origin node should copy its * partition from the tablespace/version to the final node. *

* Note that originNodeId is a DNode if (Thrift) whereas finalNodeHttpAddres is an HTTP end-point (not a DNode Id). */ @SuppressWarnings("serial") public static class BalanceAction implements Serializable { private String originNodeId; private String finalNodeHttpAddress; private String tablespace; private int partition; private long version; // Note that originNodeId is a DNode if (Thrift) whereas finalNodeHttpAddres is an HTTP end-point (not a DNode Id) public BalanceAction(String originNode, String finalNodeHttpAddress, String tablespace, int partition, long version) { this.originNodeId = originNode; this.finalNodeHttpAddress = finalNodeHttpAddress; this.tablespace = tablespace; this.partition = partition; this.version = version; } public String toString() { return originNodeId + " => " + finalNodeHttpAddress + " (" + tablespace + ", " + partition + ", " + version + ")"; } /** * Because of the semantics of this object, we consider equals another one even if the origin node is different. We * only care about the final node and the data that will be transfered. */ @Override public boolean equals(Object obj) { BalanceAction action = (BalanceAction) obj; return action.getFinalNode().equals(getFinalNode()) && action.getTablespace().equals(getTablespace()) && action.getVersion() == getVersion() && action.getPartition() == getPartition(); } @Override public int hashCode() { return getFinalNode().hashCode() ^ getTablespace().hashCode() ^ Long.valueOf(getVersion()).hashCode() ^ getPartition(); } // ---- Getters ---- // public String getOriginNode() { return originNodeId; } public String getFinalNode() { return finalNodeHttpAddress; } public String getTablespace() { return tablespace; } public int getPartition() { return partition; } public long getVersion() { return version; } } public List scanPartitions() { // get list of DNodes List aliveDNodes = context.getDNodeList(); Collections.sort(aliveDNodes); log.info(Thread.currentThread() + " - alive DNodes : " + aliveDNodes); // actions that can be taken after analyzing the current replicas / partitions List balanceActions = new ArrayList(); // we will use round robin for assigning new partitions to DNodes // so that if several BalanceAction have to be taken, they will be more or less spread int roundRobinCount = 0; Map tablespaceVersion = context.getTablespaceVersionsMap(); log.info(Thread.currentThread() + " - Tablespace versions: " + tablespaceVersion); for(Map.Entry entry : tablespaceVersion.entrySet()) { ReplicationMap replicationMap = entry.getValue().getReplicationMap(); for(ReplicationEntry rEntry : replicationMap.getReplicationEntries()) { log.info(rEntry); // for every missing replica... maybe perform a BalanceAction if(rEntry.getNodes().size() > 0) { for(int i = rEntry.getNodes().size(); i < rEntry.getExpectedReplicationFactor(); i++) { // we found an under-replicated partition! add it as candidate // we will copy the partition from the first available node in this partition String originNode = rEntry.getNodes().get(0); // ... then find the first DNode which doesn't currently hold this partition // as candidate to receive it for(int k = 0; k < aliveDNodes.size(); k++) { int roundRobinIndex = (roundRobinCount + k) % aliveDNodes.size(); String finalNode = aliveDNodes.get(roundRobinIndex); if(rEntry.getNodes().contains(finalNode)) { continue; } // we have a possible balance action // note we must exchange the DNode Id by its HTTP end-point to be able to send files there String finalHttpAddress = null; for(DNodeInfo dnode : context.getCoordinationStructures().getDNodes().values()) { if(dnode.getAddress().equals(finalNode)) { finalHttpAddress = dnode.getHttpExchangerAddress(); } } if(finalHttpAddress == null) { // race condition: DNode went down right in the middle - cancel this and try another one } else { // add balance action and break for() loop balanceActions.add(new BalanceAction(originNode, finalHttpAddress, entry.getKey() .getTablespace(), rEntry.getShard(), entry.getKey().getVersion())); roundRobinCount++; break; } } } } } } return balanceActions; } }





© 2015 - 2024 Weber Informatics LLC | Privacy Policy