7.6 KiB
7.6 KiB
启动
createDataNode
DataNode核心启动类是从createDataNode开始的。
public static DataNode createDataNode(String args[], Configuration conf,
SecureResources resources) throws IOException {
// 初始化DataNode,核心函数在makeInstance里面的new DataNode()进行初始化。
DataNode dn = instantiateDataNode(args, conf, resources);
if (dn != null) {
// 启动DataNode
dn.runDatanodeDaemon();
}
return dn;
}
makeInstance
初始化DataNode实例。
static DataNode makeInstance(Collection<StorageLocation> dataDirs,
Configuration conf, SecureResources resources) throws IOException {
List<StorageLocation> locations;
StorageLocationChecker storageLocationChecker =
new StorageLocationChecker(conf, new Timer());
try {
// 对存储路径进行检查。返回可用的位置。
locations = storageLocationChecker.check(conf, dataDirs);
} catch (InterruptedException ie) {
throw new IOException("Failed to instantiate DataNode", ie);
}
DefaultMetricsSystem.initialize("DataNode");
assert locations.size() > 0 : "number of data directories should be > 0";
// 初始化DataNode实例。在构造函数里面startDataNode比较重要，是启动DataNode的核心函数，需要重点关注。
return new DataNode(conf, locations, storageLocationChecker, resources);
}
startDataNode
void startDataNode(List<StorageLocation> dataDirectories,
SecureResources resources
) throws IOException {
// settings global for all BPs in the Data Node
this.secureResources = resources;
synchronized (this) {
this.dataDirs = dataDirectories;
}
this.dnConf = new DNConf(this);
checkSecureConfig(dnConf, getConf(), resources);
// ... 省略 ....
storage = new DataStorage();
// global DN settings
registerMXBean();
// 初始化dataXceiver服务：用于DN接受客户端和其他DN发送过来的数据的服务。
initDataXceiver();
// 初始化HTTP服务。
startInfoServer();
//TODO 待定。
pauseMonitor = new JvmPauseMonitor();
pauseMonitor.init(getConf());
pauseMonitor.start();
// BlockPoolTokenSecretManager is required to create ipc server.
this.blockPoolTokenSecretManager = new BlockPoolTokenSecretManager();
// Login is done by now. Set the DN user name.
dnUserName = UserGroupInformation.getCurrentUser().getUserName();
LOG.info("dnUserName = {}", dnUserName);
LOG.info("supergroup = {}", supergroup);
// 初始化DN的RPC调用服务。
initIpcServer();
metrics = DataNodeMetrics.create(getConf(), getDisplayName());
peerMetrics = dnConf.peerStatsEnabled ?
DataNodePeerMetrics.create(getDisplayName(), getConf()) : null;
metrics.getJvmMetrics().setPauseMonitor(pauseMonitor);
ecWorker = new ErasureCodingWorker(getConf(), this);
blockRecoveryWorker = new BlockRecoveryWorker(this);
blockPoolManager = new BlockPoolManager(this);
// DN向NN注册，其中核心的函数为doRefreshNamenodes
blockPoolManager.refreshNamenodes(getConf());
// Create the ReadaheadPool from the DataNode context so we can
// exit without having to explicitly shutdown its thread pool.
readaheadPool = ReadaheadPool.getInstance();
saslClient = new SaslDataTransferClient(dnConf.getConf(),
dnConf.saslPropsResolver, dnConf.trustedChannelResolver);
saslServer = new SaslDataTransferServer(dnConf, blockPoolTokenSecretManager);
startMetricsLogger();
if (dnConf.diskStatsEnabled) {
diskMetrics = new DataNodeDiskMetrics(this,
dnConf.outliersReportIntervalMs, getConf());
}
}
doRefreshNamenodes
主要是向NN注册当前DN。
private void doRefreshNamenodes(
Map<String, Map<String, InetSocketAddress>> addrMap,
Map<String, Map<String, InetSocketAddress>> lifelineAddrMap)
throws IOException {
Set<String> toRefresh = Sets.newLinkedHashSet();
Set<String> toAdd = Sets.newLinkedHashSet();
Set<String> toRemove;
synchronized (this) {
// Step 1. For each of the new nameservices, figure out whether
// it's an update of the set of NNs for an existing NS,
// or an entirely new nameservice.
// 判断当前DN中的nameservice是否已经存在：如果已经存在则需要刷新；否则需要添加。
for (String nameserviceId : addrMap.keySet()) {
if (bpByNameserviceId.containsKey(nameserviceId)) {
toRefresh.add(nameserviceId);
} else {
toAdd.add(nameserviceId);
}
}
// Step 2. Any nameservices we currently have but are no longer present
// need to be removed.
// 计算当前DN需要删除的nameservice
toRemove = Sets.newHashSet(Sets.difference(
bpByNameserviceId.keySet(), addrMap.keySet()));
// Step 3. 启动新的nameservice
if (!toAdd.isEmpty()) {
for (String nsToAdd : toAdd) {
Map<String, InetSocketAddress> nnIdToAddr = addrMap.get(nsToAdd);
Map<String, InetSocketAddress> nnIdToLifelineAddr =
lifelineAddrMap.get(nsToAdd);
ArrayList<InetSocketAddress> addrs =
Lists.newArrayListWithCapacity(nnIdToAddr.size());
ArrayList<String> nnIds =
Lists.newArrayListWithCapacity(nnIdToAddr.size());
ArrayList<InetSocketAddress> lifelineAddrs =
Lists.newArrayListWithCapacity(nnIdToAddr.size());
for (String nnId : nnIdToAddr.keySet()) {
addrs.add(nnIdToAddr.get(nnId));
nnIds.add(nnId);
lifelineAddrs.add(nnIdToLifelineAddr != null ?
nnIdToLifelineAddr.get(nnId) : null);
}
BPOfferService bpos = createBPOS(nsToAdd, nnIds, addrs,
lifelineAddrs);
bpByNameserviceId.put(nsToAdd, bpos);
offerServices.add(bpos);
}
}
startAll();
}
// Step 4. 停止掉老的nameservice. This happens outside
// of the synchronized(this) lock since they need to call
// back to .remove() from another thread
if (!toRemove.isEmpty()) {
for (String nsToRemove : toRemove) {
BPOfferService bpos = bpByNameserviceId.get(nsToRemove);
bpos.stop();
bpos.join();
// they will call remove on their own
}
}
// Step 5. Update nameservices whose NN list has changed
// 更新nameservices
if (!toRefresh.isEmpty()) {
for (String nsToRefresh : toRefresh) {
BPOfferService bpos = bpByNameserviceId.get(nsToRefresh);
Map<String, InetSocketAddress> nnIdToAddr = addrMap.get(nsToRefresh);
Map<String, InetSocketAddress> nnIdToLifelineAddr =
lifelineAddrMap.get(nsToRefresh);
ArrayList<InetSocketAddress> addrs =
Lists.newArrayListWithCapacity(nnIdToAddr.size());
ArrayList<InetSocketAddress> lifelineAddrs =
Lists.newArrayListWithCapacity(nnIdToAddr.size());
ArrayList<String> nnIds = Lists.newArrayListWithCapacity(
nnIdToAddr.size());
for (String nnId : nnIdToAddr.keySet()) {
addrs.add(nnIdToAddr.get(nnId));
lifelineAddrs.add(nnIdToLifelineAddr != null ?
nnIdToLifelineAddr.get(nnId) : null);
nnIds.add(nnId);
}
try {
UserGroupInformation.getLoginUser()
.doAs(new PrivilegedExceptionAction<Object>() {
@Override
public Object run() throws Exception {
// 刷新NNList 核心实现.
bpos.refreshNNList(nsToRefresh, nnIds, addrs, lifelineAddrs);
return null;
}
});
} catch (InterruptedException ex) {
IOException ioe = new IOException();
ioe.initCause(ex.getCause());
throw ioe;
}
}
}
}