/**
* 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.zookeeper.server.quorum.flexible;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.IOException;
import java.util.HashSet;
import java.util.HashMap;
import java.util.Properties;
import java.util.Map.Entry;
import org.apache.log4j.Logger;
import org.apache.zookeeper.server.quorum.QuorumPeerConfig.ConfigException;
/**
* This class implements a validator for hierarchical quorums. With this
* construction, zookeeper servers are split into disjoint groups, and
* each server has a weight. We obtain a quorum if we get more than half
* of the total weight of a group for a majority of groups.
*
* The configuration of quorums uses two parameters: group and weight.
* Groups are sets of ZooKeeper servers, and we set a group by passing
* a colon-separated list of server ids. It is also necessary to assign
* weights to server. Here is an example of a configuration that creates
* three groups and assigns a weight of 1 to each server:
*
* group.1=1:2:3
* group.2=4:5:6
* group.3=7:8:9
*
* weight.1=1
* weight.2=1
* weight.3=1
* weight.4=1
* weight.5=1
* weight.6=1
* weight.7=1
* weight.8=1
* weight.9=1
*
* Note that it is still necessary to define peers using the server keyword.
*/
public class QuorumHierarchical implements QuorumVerifier {
private static final Logger LOG = Logger.getLogger(QuorumHierarchical.class);
HashMap<Long, Long> serverWeight;
HashMap<Long, Long> serverGroup;
HashMap<Long, Long> groupWeight;
int numGroups;
/**
* This contructor requires the quorum configuration
* to be declared in a separate file, and it takes the
* file as an input parameter.
*/
public QuorumHierarchical(String filename)
throws ConfigException {
this.serverWeight = new HashMap<Long, Long>();
this.serverGroup = new HashMap<Long, Long>();
this.groupWeight = new HashMap<Long, Long>();
this.numGroups = 0;
readConfigFile(filename);
}
/**
* This constructor takes a set of properties. We use
* it in the unit test for this feature.
*/
public QuorumHierarchical(Properties qp)
throws ConfigException {
this.serverWeight = new HashMap<Long, Long>();
this.serverGroup = new HashMap<Long, Long>();
this.groupWeight = new HashMap<Long, Long>();
this.numGroups = 0;
parse(qp);
LOG.info(serverWeight.size() + ", " + serverGroup.size() + ", " + groupWeight.size());
}
/**
* This contructor takes the two hash maps needed to enable
* validating quorums. We use it with QuorumPeerConfig. That is,
* we declare weights and groups in the server configuration
* file along with the other parameters.
* @param numGroups
* @param serverWeight
* @param serverGroup
*/
public QuorumHierarchical(int numGroups,
HashMap<Long, Long> serverWeight,
HashMap<Long, Long> serverGroup)
{
this.serverWeight = serverWeight;
this.serverGroup = serverGroup;
this.groupWeight = new HashMap<Long, Long>();
this.numGroups = numGroups;
computeGroupWeight();
}
/**
* Returns the weight of a server.
*
* @param id
*/
public long getWeight(long id){
return serverWeight.get(id);
}
/**
* Reads a configration file. Called from the constructor
* that takes a file as an input.
*/
private void readConfigFile(String filename)
throws ConfigException{
File configFile = new File(filename);
LOG.info("Reading configuration from: " + configFile);
try {
if (!configFile.exists()) {
throw new IllegalArgumentException(configFile.toString()
+ " file is missing");
}
Properties cfg = new Properties();
FileInputStream in = new FileInputStream(configFile);
try {
cfg.load(in);
} finally {
in.close();
}
parse(cfg);
} catch (IOException e) {
throw new ConfigException("Error processing " + filename, e);
} catch (IllegalArgumentException e) {
throw new ConfigException("Error processing " + filename, e);
}
}
/**
* Parse properties if configuration given in a separate file.
*/
private void parse(Properties quorumProp){
for (Entry<Object, Object> entry : quorumProp.entrySet()) {
String key = entry.getKey().toString();
String value = entry.getValue().toString();
if (key.startsWith("group")) {
int dot = key.indexOf('.');
long gid = Long.parseLong(key.substring(dot + 1));
numGroups++;
String parts[] = value.split(":");
for(String s : parts){
long sid = Long.parseLong(s);
serverGroup.put(sid, gid);
}
} else if(key.startsWith("weight")) {
int dot = key.indexOf('.');
long sid = Long.parseLong(key.substring(dot + 1));
serverWeight.put(sid, Long.parseLong(value));
}
}
computeGroupWeight();
}
/**
* This method pre-computes the weights of groups to speed up processing
* when validating a given set. We compute the weights of groups in
* different places, so we have a separate method.
*/
private void computeGroupWeight(){
for(long sid : serverGroup.keySet()){
Long gid = serverGroup.get(sid);
if(!groupWeight.containsKey(gid))
groupWeight.put(gid, serverWeight.get(sid));
else {
long totalWeight = serverWeight.get(sid) + groupWeight.get(gid);
groupWeight.put(gid, totalWeight);
}
}
/*
* Do not consider groups with weight zero
*/
for(long weight: groupWeight.values()){
LOG.debug("Group weight: " + weight);
if(weight == ((long) 0)){
numGroups--;
LOG.debug("One zero-weight group: " + 1 + ", " + numGroups);
}
}
}
/**
* Verifies if a given set is a quorum.
*/
public boolean containsQuorum(HashSet<Long> set){
HashMap<Long, Long> expansion = new HashMap<Long, Long>();
/*
* Adds up weights per group
*/
if(set.size() == 0) return false;
else LOG.debug("Set size: " + set.size());
for(long sid : set){
Long gid = serverGroup.get(sid);
if(!expansion.containsKey(gid))
expansion.put(gid, serverWeight.get(sid));
else {
long totalWeight = serverWeight.get(sid) + expansion.get(gid);
expansion.put(gid, totalWeight);
}
}
/*
* Check if all groups have majority
*/
int majGroupCounter = 0;
for(long gid : expansion.keySet()) {
LOG.debug("Group info: " + expansion.get(gid) + ", " + gid + ", " + groupWeight.get(gid));
if(expansion.get(gid) > (groupWeight.get(gid) / 2) )
majGroupCounter++;
}
LOG.debug("Majority group counter: " + majGroupCounter + ", " + numGroups);
if((majGroupCounter > (numGroups / 2))){
LOG.debug("Positive set size: " + set.size());
return true;
}
else {
LOG.debug("Negative set size: " + set.size());
return false;
}
}
}