对kafka中zookeeper启动过程解析
首先kafka中zookeeper启动的命令是：
/usr/local/kafka/bin/zookeeper-server-start.sh /usr/local/kafka/config/zookeeper.properties &
查看zookeeper-server-start.sh里面最后一行是：
exec $base_dir/kafka-run-class.sh $EXTRA_ARGS org.apache.zookeeper.server.quorum.QuorumPeerMain $@
它去执行了org.apache.zookeeper.server.quorum.QuorumPeerMain 这个main方法，那我们就跑到这个main里面去看下究竟吧
/**
* To start the replicated server specify the configuration file name on
* the command line.
* @param args path to the configfile
*/
public static void main(String[] args) {
QuorumPeerMain main = new QuorumPeerMain();
try {
main.initializeAndRun(args);
} catch (IllegalArgumentException e) {
LOG.fatal("Invalid arguments, exiting abnormally", e);
LOG.info(USAGE);
System.err.println(USAGE);
System.exit(2);
} catch (ConfigException e) {
LOG.fatal("Invalid config, exiting abnormally", e);
System.err.println("Invalid config, exiting abnormally");
System.exit(2);
} catch (Exception e) {
LOG.fatal("Unexpected exception, exiting abnormally", e);
System.exit(1);
}
LOG.info("Exiting normally");
System.exit(0);
}
protected void initializeAndRun(String[] args)
throws ConfigException, IOException
{
QuorumPeerConfig config = new QuorumPeerConfig();
if (args.length == 1) {
config.parse(args[0]);
}
if (args.length == 1 && config.servers.size() > 0) {
runFromConfig(config);
} else {
LOG.warn("Either no config or no quorum defined in config, running "
+ " in standalone mode");
// there is only server in the quorum -- run as standalone
ZooKeeperServerMain.main(args);
}
}
从启动的log上看到:WARN Either no config or no quorum defined in config, running in standalone mode (org.apache.zookeeper.server.quorum.QuorumPeerMain)接下来让我们去ZooKeeperServerMain.main(args)继续看吧
protected void initializeAndRun(String[] args)
throws ConfigException, IOException
{
try {
ManagedUtil.registerLog4jMBeans();
} catch (JMException e) {
LOG.warn("Unable to register log4j JMX control", e);
}
ServerConfig config = new ServerConfig();
if (args.length == 1) {
config.parse(args[0]);
} else {
config.parse(args);
}
runFromConfig(config);
}
ServerConfig去读取配置文件
public void parseProperties(Properties zkProp)
throws IOException, ConfigException {
int clientPort = 0;
String clientPortAddress = null;
for (Entry<Object, Object> entry : zkProp.entrySet()) {
String key = entry.getKey().toString().trim();
String value = entry.getValue().toString().trim();
if (key.equals("dataDir")) {
dataDir = value;
} else if (key.equals("dataLogDir")) {
dataLogDir = value;
} else if (key.equals("clientPort")) {
clientPort = Integer.parseInt(value);
} else if (key.equals("clientPortAddress")) {
clientPortAddress = value.trim();
} else if (key.equals("tickTime")) {
tickTime = Integer.parseInt(value);
} else if (key.equals("maxClientCnxns")) {
maxClientCnxns = Integer.parseInt(value);
} else if (key.equals("minSessionTimeout")) {
minSessionTimeout = Integer.parseInt(value);
} else if (key.equals("maxSessionTimeout")) {
maxSessionTimeout = Integer.parseInt(value);
} else if (key.equals("initLimit")) {
initLimit = Integer.parseInt(value);
} else if (key.equals("syncLimit")) {
syncLimit = Integer.parseInt(value);
} else if (key.equals("electionAlg")) {
electionAlg = Integer.parseInt(value);
} else if (key.equals("peerType")) {
if (value.toLowerCase().equals("observer")) {
peerType = LearnerType.OBSERVER;
} else if (value.toLowerCase().equals("participant")) {
peerType = LearnerType.PARTICIPANT;
} else
{
throw new ConfigException("Unrecognised peertype: " + value);
}
} else if (key.startsWith("server.")) {
int dot = key.indexOf('.');
long sid = Long.parseLong(key.substring(dot + 1));
String parts[] = value.split(":");
if ((parts.length != 2) && (parts.length != 3) && (parts.length !=4)) {
LOG.error(value
+ " does not have the form host:port or host:port:port " +
" or host:port:port:type");
}
InetSocketAddress addr = new InetSocketAddress(parts[0],
Integer.parseInt(parts[1]));
if (parts.length == 2) {
servers.put(Long.valueOf(sid), new QuorumServer(sid, addr));
} else if (parts.length == 3) {
InetSocketAddress electionAddr = new InetSocketAddress(
parts[0], Integer.parseInt(parts[2]));
servers.put(Long.valueOf(sid), new QuorumServer(sid, addr,
electionAddr));
} else if (parts.length == 4) {
InetSocketAddress electionAddr = new InetSocketAddress(
parts[0], Integer.parseInt(parts[2]));
LearnerType type = LearnerType.PARTICIPANT;
if (parts[3].toLowerCase().equals("observer")) {
type = LearnerType.OBSERVER;
observers.put(Long.valueOf(sid), new QuorumServer(sid, addr,
electionAddr,type));
} else if (parts[3].toLowerCase().equals("participant")) {
type = LearnerType.PARTICIPANT;
servers.put(Long.valueOf(sid), new QuorumServer(sid, addr,
electionAddr,type));
} else {
throw new ConfigException("Unrecognised peertype: " + value);
}
}
} else 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);
if(serverGroup.containsKey(sid))
throw new ConfigException("Server " + sid + "is in multiple groups");
else
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));
} else {
System.setProperty("zookeeper." + key, value);
}
}
if (dataDir == null) {
throw new IllegalArgumentException("dataDir is not set");
}
if (dataLogDir == null) {
dataLogDir = dataDir;
} else {
if (!new File(dataLogDir).isDirectory()) {
throw new IllegalArgumentException("dataLogDir " + dataLogDir
+ " is missing.");
}
}
if (clientPort == 0) {
throw new IllegalArgumentException("clientPort is not set");
}
if (clientPortAddress != null) {
this.clientPortAddress = new InetSocketAddress(
InetAddress.getByName(clientPortAddress), clientPort);
} else {
this.clientPortAddress = new InetSocketAddress(clientPort);
}
if (tickTime == 0) {
throw new IllegalArgumentException("tickTime is not set");
}
if (minSessionTimeout > maxSessionTimeout) {
throw new IllegalArgumentException(
"minSessionTimeout must not be larger than maxSessionTimeout");
}
if (servers.size() == 0) {
if (observers.size() > 0) {
throw new IllegalArgumentException("Observers w/o participants is an invalid configuration");
}
// Not a quorum configuration so return immediately - not an error
// case (for b/w compatibility), server will default to standalone
// mode.
return;
} else if (servers.size() == 1) {
if (observers.size() > 0) {
throw new IllegalArgumentException("Observers w/o quorum is an invalid configuration");
}
// HBase currently adds a single server line to the config, for
// b/w compatibility reasons we need to keep this here.
LOG.error("Invalid configuration, only one server specified (ignoring)");
servers.clear();
} else if (servers.size() > 1) {
if (servers.size() == 2) {
LOG.warn("No server failure will be tolerated. " +
"You need at least 3 servers.");
} else if (servers.size() % 2 == 0) {
LOG.warn("Non-optimial configuration, consider an odd number of servers.");
}
if (initLimit == 0) {
throw new IllegalArgumentException("initLimit is not set");
}
if (syncLimit == 0) {
throw new IllegalArgumentException("syncLimit is not set");
}
/*
* If using FLE, then every server requires a separate election
* port.
*/
if (electionAlg != 0) {
for (QuorumServer s : servers.values()) {
if (s.electionAddr == null)
throw new IllegalArgumentException(
"Missing election port for server: " + s.id);
}
}
/*
* Default of quorum config is majority
*/
if(serverGroup.size() > 0){
if(servers.size() != serverGroup.size())
throw new ConfigException("Every server must be in exactly one group");
/*
* The deafult weight of a server is 1
*/
for(QuorumServer s : servers.values()){
if(!serverWeight.containsKey(s.id))
serverWeight.put(s.id, (long) 1);
}
/*
* Set the quorumVerifier to be QuorumHierarchical
*/
quorumVerifier = new QuorumHierarchical(numGroups,
serverWeight, serverGroup);
} else {
/*
* The default QuorumVerifier is QuorumMaj
*/
LOG.info("Defaulting to majority quorums");
quorumVerifier = new QuorumMaj(servers.size());
}
// Now add observers to servers, once the quorums have been
// figured out
servers.putAll(observers);
File myIdFile = new File(dataDir, "myid");
if (!myIdFile.exists()) {
throw new IllegalArgumentException(myIdFile.toString()
+ " file is missing");
}
BufferedReader br = new BufferedReader(new FileReader(myIdFile));
String myIdString;
try {
myIdString = br.readLine();
} finally {
br.close();
}
try {
serverId = Long.parseLong(myIdString);
} catch (NumberFormatException e) {
throw new IllegalArgumentException("serverid " + myIdString
+ " is not a number");
}
}
}这一大段都是关于解析配置文件，所以大家在配置文件的时候不要配错了。
/**
* Run from a ServerConfig.
* @param config ServerConfig to use.
* @throws IOException
*/
public void runFromConfig(ServerConfig config) throws IOException {
LOG.info("Starting server");
try {
// Note that this thread isn't going to be doing anything else,
// so rather than spawning another thread, we will just call
// run() in this thread.
// create a file logger url from the command line args
ZooKeeperServer zkServer = new ZooKeeperServer();
FileTxnSnapLog ftxn = new FileTxnSnapLog(new
File(config.dataLogDir), new File(config.dataDir));
zkServer.setTxnLogFactory(ftxn);
zkServer.setTickTime(config.tickTime);
zkServer.setMinSessionTimeout(config.minSessionTimeout);
zkServer.setMaxSessionTimeout(config.maxSessionTimeout);
cnxnFactory = new NIOServerCnxn.Factory(config.getClientPortAddress(),
config.getMaxClientCnxns());
cnxnFactory.startup(zkServer);
cnxnFactory.join();
if (zkServer.isRunning()) {
zkServer.shutdown();
}
} catch (InterruptedException e) {
// warn, but generally this is ok
LOG.warn("Server interrupted", e);
}
}
接下来继续看
cnxnFactory.startup(zkServer);代码是要开始
* This class handles communication with clients using NIO. There is one per * client, but only one thread doing the communication.
从字面上的意思就是开启一个线程去监控客户端与zookeeper的socket的最大连接数，
注：zookeeper的最大连接数是在zookeeper.properties的maxClientCnxns=150设置。
若超出最大连接数将会导致socket close
</pre><p><pre name="code" class="java"> public void deserialize(DataTree dt, Map<Long, Integer> sessions,
InputArchive ia) throws IOException {
FileHeader header = new FileHeader();
header.deserialize(ia, "fileheader");
if (header.getMagic() != SNAP_MAGIC) {
throw new IOException("mismatching magic headers "
+ header.getMagic() +
" != " + FileSnap.SNAP_MAGIC);
}
SerializeUtils.deserializeSnapshot(dt,ia,sessions);
}这一段代码是去读取本地文件，获取到上一次断掉的sessions点，是反序列话读取的，就是从最后一个读取并且用tree来排列
public void startup() {
createSessionTracker();
setupRequestProcessors();
registerJMX();
synchronized (this) {
running = true;
notifyAll();
}
}这里将启动启动线程来管理session
太多了，先到这里，有什么问题或者意见直接留言。
接下来有时间会继续进行优化和更新。
接下来将会去kafka本身是怎么利用zookeeper来实现管理topic数据的，并且还要继续了解kafka生产消息和消费消息的原理，