Zookeeper source code interpretation – a preliminary analysis of the node startup process, has learned the overall process of zooKeeper node startup, and finally analyzes the startup steps of QuorumPeer. This article continues to analyze the startup process of QuorumPeer from the source code.
Let’s revisit the runFromConfig method of QuorumPeerMain:
public void runFromConfig(QuorumPeerConfig config) throws IOException, AdminServerException {
try {
ManagedUtil.registerLog4jMBeans();
} catch (JMException e) {
LOG.warn("Unable to register log4j JMX control", e);
}
LOG.info("Starting quorum peer");
MetricsProvider metricsProvider;
try {
metricsProvider = MetricsProviderBootstrap.startMetricsProvider(
config.getMetricsProviderClassName(),
config.getMetricsProviderConfiguration());
} catch (MetricsProviderLifeCycleException error) {
throw new IOException("Cannot boot MetricsProvider " + config.getMetricsProviderClassName(), error);
}
try {
ServerMetrics.metricsProviderInitialized(metricsProvider);
ServerCnxnFactory cnxnFactory = null;
ServerCnxnFactory secureCnxnFactory = null;
if(config.getClientPortAddress() ! =null) {
cnxnFactory = ServerCnxnFactory.createFactory();
cnxnFactory.configure(config.getClientPortAddress(), config.getMaxClientCnxns(), config.getClientPortListenBacklog(), false);
}
if(config.getSecureClientPortAddress() ! =null) {
secureCnxnFactory = ServerCnxnFactory.createFactory();
secureCnxnFactory.configure(config.getSecureClientPortAddress(), config.getMaxClientCnxns(), config.getClientPortListenBacklog(), true);
}
quorumPeer = getQuorumPeer();
quorumPeer.setTxnFactory(new FileTxnSnapLog(config.getDataLogDir(), config.getDataDir()));
quorumPeer.enableLocalSessions(config.areLocalSessionsEnabled());
quorumPeer.enableLocalSessionsUpgrading(config.isLocalSessionsUpgradingEnabled());
//quorumPeer.setQuorumPeers(config.getAllMembers());
quorumPeer.setElectionType(config.getElectionAlg());
quorumPeer.setMyid(config.getServerId());
quorumPeer.setTickTime(config.getTickTime());
quorumPeer.setMinSessionTimeout(config.getMinSessionTimeout());
quorumPeer.setMaxSessionTimeout(config.getMaxSessionTimeout());
quorumPeer.setInitLimit(config.getInitLimit());
quorumPeer.setSyncLimit(config.getSyncLimit());
quorumPeer.setConnectToLearnerMasterLimit(config.getConnectToLearnerMasterLimit());
quorumPeer.setObserverMasterPort(config.getObserverMasterPort());
quorumPeer.setConfigFileName(config.getConfigFilename());
quorumPeer.setClientPortListenBacklog(config.getClientPortListenBacklog());
quorumPeer.setZKDatabase(new ZKDatabase(quorumPeer.getTxnFactory()));
quorumPeer.setQuorumVerifier(config.getQuorumVerifier(), false);
if(config.getLastSeenQuorumVerifier() ! =null) {
quorumPeer.setLastSeenQuorumVerifier(config.getLastSeenQuorumVerifier(), false);
}
quorumPeer.initConfigInZKDatabase();
quorumPeer.setCnxnFactory(cnxnFactory);
quorumPeer.setSecureCnxnFactory(secureCnxnFactory);
quorumPeer.setSslQuorum(config.isSslQuorum());
quorumPeer.setUsePortUnification(config.shouldUsePortUnification());
quorumPeer.setLearnerType(config.getPeerType());
quorumPeer.setSyncEnabled(config.getSyncEnabled());
quorumPeer.setQuorumListenOnAllIPs(config.getQuorumListenOnAllIPs());
if (config.sslQuorumReloadCertFiles) {
quorumPeer.getX509Util().enableCertFileReloading();
}
quorumPeer.setMultiAddressEnabled(config.isMultiAddressEnabled());
quorumPeer.setMultiAddressReachabilityCheckEnabled(config.isMultiAddressReachabilityCheckEnabled());
quorumPeer.setMultiAddressReachabilityCheckTimeoutMs(config.getMultiAddressReachabilityCheckTimeoutMs());
// sets quorum sasl authentication configurations
quorumPeer.setQuorumSaslEnabled(config.quorumEnableSasl);
if (quorumPeer.isQuorumSaslAuthEnabled()) {
quorumPeer.setQuorumServerSaslRequired(config.quorumServerRequireSasl);
quorumPeer.setQuorumLearnerSaslRequired(config.quorumLearnerRequireSasl);
quorumPeer.setQuorumServicePrincipal(config.quorumServicePrincipal);
quorumPeer.setQuorumServerLoginContext(config.quorumServerLoginContext);
quorumPeer.setQuorumLearnerLoginContext(config.quorumLearnerLoginContext);
}
quorumPeer.setQuorumCnxnThreadsSize(config.quorumCnxnThreadsSize);
quorumPeer.initialize();
if (config.jvmPauseMonitorToRun) {
quorumPeer.setJvmPauseMonitor(new JvmPauseMonitor(config));
}
quorumPeer.start();
ZKAuditProvider.addZKStartStopAuditLog();
quorumPeer.join();
} catch (InterruptedException e) {
// warn, but generally this is ok
LOG.warn("Quorum Peer interrupted", e);
} finally {
if(metricsProvider ! =null) {
try {
metricsProvider.stop();
} catch (Throwable error) {
LOG.warn("Error while stopping metrics", error); }}}}// @VisibleForTesting
protected QuorumPeer getQuorumPeer(a) throws SaslException {
return new QuorumPeer();
}
Copy the codeThese include the following two important steps:
-
1) Create the ServerCnxnFactory object and configure it
-
2) Create a New QuorumPeer object, set its properties, then start and wait to stop
As we know, ZooKeeper is a distributed coordination service cluster, which requires network communication between cluster nodes and access from external clients. Therefore, each node in the ZooKeeper cluster needs to serve as a communication server to receive and process access requests from other nodes and external clients. ServerCnxnFactory is the object used to create the communication server.
Let’s take a look at the createFactory method:
public static ServerCnxnFactory createFactory(a) throws IOException {
String serverCnxnFactoryName = System.getProperty(ZOOKEEPER_SERVER_CNXN_FACTORY);
if (serverCnxnFactoryName == null) {
serverCnxnFactoryName = NIOServerCnxnFactory.class.getName();
}
try {
ServerCnxnFactory serverCnxnFactory = (ServerCnxnFactory) Class.forName(serverCnxnFactoryName)
.getDeclaredConstructor()
.newInstance();
LOG.info("Using {} as server connection factory", serverCnxnFactoryName);
return serverCnxnFactory;
} catch (Exception e) {
IOException ioe = new IOException("Couldn't instantiate " + serverCnxnFactoryName, e);
throwioe; }}Copy the codeHere USES a reflection mechanism, the first access to environment variables to zookeeper. ServerCnxnFactory implementation class name, if you don’t have to configure this variable’s value, use the default implementation class NIOServerCnxnFactory, then by default constructor instantiate the object.
The default constructor for NIOServerCnxnFactory is an empty implementation, just a static block of code for a class that deals with the JVM bug that Selector. Open () may have null Pointers, and sets the directBufferBytes property value.
Then we call the config method of ServerCnxnFactory for parameter configuration. We enter the config method of the default implementation class NIOServerCnxnFactory.
@Override
public void configure(InetSocketAddress addr, int maxcc, int backlog, boolean secure) throws IOException {
if (secure) {
throw new UnsupportedOperationException("SSL isn't supported in NIOServerCnxn");
}
configureSaslLogin();
maxClientCnxns = maxcc;
initMaxCnxns();
sessionlessCnxnTimeout = Integer.getInteger(ZOOKEEPER_NIO_SESSIONLESS_CNXN_TIMEOUT, 10000);
// We also use the sessionlessCnxnTimeout as expiring interval for
// cnxnExpiryQueue. These don't need to be the same, but the expiring
// interval passed into the ExpiryQueue() constructor below should be
// less than or equal to the timeout.
cnxnExpiryQueue = new ExpiryQueue<NIOServerCnxn>(sessionlessCnxnTimeout);
expirerThread = new ConnectionExpirerThread();
int numCores = Runtime.getRuntime().availableProcessors();
// 32 cores sweet spot seems to be 4 selector threads
numSelectorThreads = Integer.getInteger(
ZOOKEEPER_NIO_NUM_SELECTOR_THREADS,
Math.max((int) Math.sqrt((float) numCores / 2), 1));
if (numSelectorThreads < 1) {
throw new IOException("numSelectorThreads must be at least 1");
}
numWorkerThreads = Integer.getInteger(ZOOKEEPER_NIO_NUM_WORKER_THREADS, 2 * numCores);
workerShutdownTimeoutMS = Long.getLong(ZOOKEEPER_NIO_SHUTDOWN_TIMEOUT, 5000);
String logMsg = "Configuring NIO connection handler with "
+ (sessionlessCnxnTimeout / 1000) + "s sessionless connection timeout, "
+ numSelectorThreads + " selector thread(s), "
+ (numWorkerThreads > 0 ? numWorkerThreads : "no") + " worker threads, and "
+ (directBufferBytes == 0 ? "gathered writes." : ("" + (directBufferBytes / 1024) + " kB direct buffers."));
LOG.info(logMsg);
for (int i = 0; i < numSelectorThreads; ++i) {
selectorThreads.add(new SelectorThread(i));
}
listenBacklog = backlog;
this.ss = ServerSocketChannel.open();
ss.socket().setReuseAddress(true);
LOG.info("binding to port {}", addr);
if (listenBacklog == -1) {
ss.socket().bind(addr);
} else {
ss.socket().bind(addr, listenBacklog);
}
ss.configureBlocking(false);
acceptThread = new AcceptThread(ss, addr, selectorThreads);
}
Copy the codeIt turns out that not only does it do some property configuration, but it also creates a server channel and creates various threads, so let’s look at that one by one.
- Create a ConnectionExpirerThread to close a connection that no longer has a session.
- Create multiple SelectorThread threads
- Enable ServerSocketChannel and bind the specified port. The default port is 2181
- Create the AcceptThread thread
The single-reactor multithreaded model is adopted, which is roughly as follows:
The above is just the preparation work of network communication, it can not work.
Let’s look at creating a QuorumPeer object.
1) Create a QuorumPeer object
An AdminServer object is created, implemented by default as the JettyAdminServer object, and the Jetty server is started to receive command requests and execute commands.
2) Set various properties of the QuorumPeer object
quorumPeer.setTxnFactory(new FileTxnSnapLog(config.getDataLogDir(), config.getDataDir()));
Transaction log and snapshot file handlers are set up
quorumPeer.setMyid(config.getServerId());
Example Set controller Myid
3) Start QuorumPeer
@Override
public synchronized void start(a) {
if(! getView().containsKey(myid)) {throw new RuntimeException("My id " + myid + " not in the peer list");
}
loadDataBase();
startServerCnxnFactory();
try {
adminServer.start();
} catch (AdminServerException e) {
LOG.warn("Problem starting AdminServer", e);
System.out.println(e);
}
startLeaderElection();
startJvmPauseMonitor();
super.start();
}
Copy the codeHere are the key points to analyze in this article. Let’s take a look at the steps:
- LoadDataBase starts to recover data from snapshots and transaction logs
- StartServerCnxnFactory Starts the NIO server
- StartLeaderElection Prepares to select a leader
- Execute the run method
LoadDataBase restores data from a snapshot file on the local disk to an in-memory tree and obtains the maximum valid ZXID.
Each of the above steps is complicated, so there is time to analyze it separately.