序
本文主要研究一下flink的BlobServer
BlobServer
flink-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/blob/BlobServer.java
public class BlobServer extends Thread implements BlobService, BlobWriter, PermanentBlobService, TransientBlobService {
/** The log object used for debugging. */
private static final Logger LOG = LoggerFactory.getLogger(BlobServer.class);
/** Counter to generate unique names for temporary files. */
private final AtomicLong tempFileCounter = new AtomicLong(0);
/** The server socket listening for incoming connections. */
private final ServerSocket serverSocket;
/** Blob Server configuration. */
private final Configuration blobServiceConfiguration;
/** Indicates whether a shutdown of server component has been requested. */
private final AtomicBoolean shutdownRequested = new AtomicBoolean();
/** Root directory for local file storage. */
private final File storageDir;
/** Blob store for distributed file storage, e.g. in HA. */
private final BlobStore blobStore;
/** Set of currently running threads. */
private final Set<BlobServerConnection> activeConnections = new HashSet<>();
/** The maximum number of concurrent connections. */
private final int maxConnections;
/** Lock guarding concurrent file accesses. */
private final ReadWriteLock readWriteLock;
/**
* Shutdown hook thread to ensure deletion of the local storage directory.
*/
private final Thread shutdownHook;
// --------------------------------------------------------------------------------------------
/**
* Map to store the TTL of each element stored in the local storage, i.e. via one of the {@link
* #getFile} methods.
**/
private final ConcurrentHashMap<Tuple2<JobID, TransientBlobKey>, Long> blobExpiryTimes =
new ConcurrentHashMap<>();
/** Time interval (ms) to run the cleanup task; also used as the default TTL. */
private final long cleanupInterval;
/**
* Timer task to execute the cleanup at regular intervals.
*/
private final Timer cleanupTimer;
/**
* Instantiates a new BLOB server and binds it to a free network port.
*
* @param config Configuration to be used to instantiate the BlobServer
* @param blobStore BlobStore to store blobs persistently
*
* @throws IOException
* thrown if the BLOB server cannot bind to a free network port or if the
* (local or distributed) file storage cannot be created or is not usable
*/
public BlobServer(Configuration config, BlobStore blobStore) throws IOException {
this.blobServiceConfiguration = checkNotNull(config);
this.blobStore = checkNotNull(blobStore);
this.readWriteLock = new ReentrantReadWriteLock();
// configure and create the storage directory
this.storageDir = BlobUtils.initLocalStorageDirectory(config);
LOG.info("Created BLOB server storage directory {}", storageDir);
// configure the maximum number of concurrent connections
final int maxConnections = config.getInteger(BlobServerOptions.FETCH_CONCURRENT);
if (maxConnections >= 1) {
this.maxConnections = maxConnections;
}
else {
LOG.warn("Invalid value for maximum connections in BLOB server: {}. Using default value of {}",
maxConnections, BlobServerOptions.FETCH_CONCURRENT.defaultValue());
this.maxConnections = BlobServerOptions.FETCH_CONCURRENT.defaultValue();
}
// configure the backlog of connections
int backlog = config.getInteger(BlobServerOptions.FETCH_BACKLOG);
if (backlog < 1) {
LOG.warn("Invalid value for BLOB connection backlog: {}. Using default value of {}",
backlog, BlobServerOptions.FETCH_BACKLOG.defaultValue());
backlog = BlobServerOptions.FETCH_BACKLOG.defaultValue();
}
// Initializing the clean up task
this.cleanupTimer = new Timer(true);
this.cleanupInterval = config.getLong(BlobServerOptions.CLEANUP_INTERVAL) * 1000;
this.cleanupTimer
.schedule(new TransientBlobCleanupTask(blobExpiryTimes, readWriteLock.writeLock(),
storageDir, LOG), cleanupInterval, cleanupInterval);
this.shutdownHook = ShutdownHookUtil.addShutdownHook(this, getClass().getSimpleName(), LOG);
// ----------------------- start the server -------------------
final String serverPortRange = config.getString(BlobServerOptions.PORT);
final Iterator<Integer> ports = NetUtils.getPortRangeFromString(serverPortRange);
final ServerSocketFactory socketFactory;
if (SSLUtils.isInternalSSLEnabled(config) && config.getBoolean(BlobServerOptions.SSL_ENABLED)) {
try {
socketFactory = SSLUtils.createSSLServerSocketFactory(config);
}
catch (Exception e) {
throw new IOException("Failed to initialize SSL for the blob server", e);
}
}
else {
socketFactory = ServerSocketFactory.getDefault();
}
final int finalBacklog = backlog;
this.serverSocket = NetUtils.createSocketFromPorts(ports,
(port) -> socketFactory.createServerSocket(port, finalBacklog));
if (serverSocket == null) {
throw new IOException("Unable to open BLOB Server in specified port range: " + serverPortRange);
}
// start the server thread
setName("BLOB Server listener at " + getPort());
setDaemon(true);
if (LOG.isInfoEnabled()) {
LOG.info("Started BLOB server at {}:{} - max concurrent requests: {} - max backlog: {}",
serverSocket.getInetAddress().getHostAddress(), getPort(), maxConnections, backlog);
}
}
//......
@Override
public void run() {
try {
while (!this.shutdownRequested.get()) {
BlobServerConnection conn = new BlobServerConnection(serverSocket.accept(), this);
try {
synchronized (activeConnections) {
while (activeConnections.size() >= maxConnections) {
activeConnections.wait(2000);
}
activeConnections.add(conn);
}
conn.start();
conn = null;
}
finally {
if (conn != null) {
conn.close();
synchronized (activeConnections) {
activeConnections.remove(conn);
}
}
}
}
}
catch (Throwable t) {
if (!this.shutdownRequested.get()) {
LOG.error("BLOB server stopped working. Shutting down", t);
try {
close();
} catch (Throwable closeThrowable) {
LOG.error("Could not properly close the BlobServer.", closeThrowable);
}
}
}
}
/**
* Shuts down the BLOB server.
*/
@Override
public void close() throws IOException {
cleanupTimer.cancel();
if (shutdownRequested.compareAndSet(false, true)) {
Exception exception = null;
try {
this.serverSocket.close();
}
catch (IOException ioe) {
exception = ioe;
}
// wake the thread up, in case it is waiting on some operation
interrupt();
try {
join();
}
catch (InterruptedException ie) {
Thread.currentThread().interrupt();
LOG.debug("Error while waiting for this thread to die.", ie);
}
synchronized (activeConnections) {
if (!activeConnections.isEmpty()) {
for (BlobServerConnection conn : activeConnections) {
LOG.debug("Shutting down connection {}.", conn.getName());
conn.close();
}
activeConnections.clear();
}
}
// Clean up the storage directory
try {
FileUtils.deleteDirectory(storageDir);
}
catch (IOException e) {
exception = ExceptionUtils.firstOrSuppressed(e, exception);
}
// Remove shutdown hook to prevent resource leaks
ShutdownHookUtil.removeShutdownHook(shutdownHook, getClass().getSimpleName(), LOG);
if (LOG.isInfoEnabled()) {
LOG.info("Stopped BLOB server at {}:{}", serverSocket.getInetAddress().getHostAddress(), getPort());
}
ExceptionUtils.tryRethrowIOException(exception);
}
}
//......
}- BlobServer继承了Thread，同时实现了BlobService、BlobWriter、PermanentBlobService、TransientBlobService接口
- 其构造器使用DefaultServerSocketFactory创建了ServerSocket，同时使用ShutdownHookUtil.addShutdownHook注册了shutdownHook，在shutdown的时候会调用close方法
- 重写了Thread的run方法，该方法在没有接收到shutdown请求的时候，会不断循环等待serverSocket.accept()，然后创建BlobServerConnection，如果当前activeConnections超过了maxConnections则会不断循环等待2000毫秒，之后将连接维护到activeConnections，然后调用conn.start()
BlobServerConnection
flink-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/blob/BlobServerConnection.java
class BlobServerConnection extends Thread {
/** The log object used for debugging. */
private static final Logger LOG = LoggerFactory.getLogger(BlobServerConnection.class);
/** The socket to communicate with the client. */
private final Socket clientSocket;
/** The BLOB server. */
private final BlobServer blobServer;
/** Read lock to synchronize file accesses. */
private final Lock readLock;
BlobServerConnection(Socket clientSocket, BlobServer blobServer) {
super("BLOB connection for " + clientSocket.getRemoteSocketAddress());
setDaemon(true);
this.clientSocket = clientSocket;
this.blobServer = checkNotNull(blobServer);
ReadWriteLock readWriteLock = blobServer.getReadWriteLock();
this.readLock = readWriteLock.readLock();
}
// --------------------------------------------------------------------------------------------
// Connection / Thread methods
// --------------------------------------------------------------------------------------------
/**
* Main connection work method. Accepts requests until the other side closes the connection.
*/
@Override
public void run() {
try {
final InputStream inputStream = this.clientSocket.getInputStream();
final OutputStream outputStream = this.clientSocket.getOutputStream();
while (true) {
// Read the requested operation
final int operation = inputStream.read();
if (operation < 0) {
// done, no one is asking anything from us
return;
}
switch (operation) {
case PUT_OPERATION:
put(inputStream, outputStream, new byte[BUFFER_SIZE]);
break;
case GET_OPERATION:
get(inputStream, outputStream, new byte[BUFFER_SIZE]);
break;
default:
throw new IOException("Unknown operation " + operation);
}
}
}
catch (SocketException e) {
// this happens when the remote site closes the connection
LOG.debug("Socket connection closed", e);
}
catch (Throwable t) {
LOG.error("Error while executing BLOB connection.", t);
}
finally {
closeSilently(clientSocket, LOG);
blobServer.unregisterConnection(this);
}
}
/**
* Closes the connection socket and lets the thread exit.
*/
public void close() {
closeSilently(clientSocket, LOG);
interrupt();
}
// --------------------------------------------------------------------------------------------
// Actions
// --------------------------------------------------------------------------------------------
private void get(InputStream inputStream, OutputStream outputStream, byte[] buf) throws IOException {
/*
* Retrieve the file from the (distributed?) BLOB store and store it
* locally, then send it to the service which requested it.
*
* Instead, we could send it from the distributed store directly but
* chances are high that if there is one request, there will be more
* so a local cache makes more sense.
*/
final File blobFile;
final JobID jobId;
final BlobKey blobKey;
try {
// read HEADER contents: job ID, key, HA mode/permanent or transient BLOB
final int mode = inputStream.read();
if (mode < 0) {
throw new EOFException("Premature end of GET request");
}
// Receive the jobId and key
if (mode == JOB_UNRELATED_CONTENT) {
jobId = null;
} else if (mode == JOB_RELATED_CONTENT) {
byte[] jidBytes = new byte[JobID.SIZE];
readFully(inputStream, jidBytes, 0, JobID.SIZE, "JobID");
jobId = JobID.fromByteArray(jidBytes);
} else {
throw new IOException("Unknown type of BLOB addressing: " + mode + '.');
}
blobKey = BlobKey.readFromInputStream(inputStream);
checkArgument(blobKey instanceof TransientBlobKey || jobId != null,
"Invalid BLOB addressing for permanent BLOBs");
if (LOG.isDebugEnabled()) {
LOG.debug("Received GET request for BLOB {}/{} from {}.", jobId,
blobKey, clientSocket.getInetAddress());
}
// the file's (destined) location at the BlobServer
blobFile = blobServer.getStorageLocation(jobId, blobKey);
// up to here, an error can give a good message
}
catch (Throwable t) {
LOG.error("GET operation from {} failed.", clientSocket.getInetAddress(), t);
try {
writeErrorToStream(outputStream, t);
}
catch (IOException e) {
// since we are in an exception case, it means that we could not send the error
// ignore this
}
clientSocket.close();
return;
}
try {
readLock.lock();
try {
// copy the file to local store if it does not exist yet
try {
blobServer.getFileInternal(jobId, blobKey, blobFile);
// enforce a 2GB max for now (otherwise the protocol's length field needs to be increased)
if (blobFile.length() > Integer.MAX_VALUE) {
throw new IOException("BLOB size exceeds the maximum size (2 GB).");
}
outputStream.write(RETURN_OKAY);
} catch (Throwable t) {
LOG.error("GET operation failed for BLOB {}/{} from {}.", jobId,
blobKey, clientSocket.getInetAddress(), t);
try {
writeErrorToStream(outputStream, t);
} catch (IOException e) {
// since we are in an exception case, it means that we could not send the error
// ignore this
}
clientSocket.close();
return;
}
// from here on, we started sending data, so all we can do is close the connection when something happens
int blobLen = (int) blobFile.length();
writeLength(blobLen, outputStream);
try (FileInputStream fis = new FileInputStream(blobFile)) {
int bytesRemaining = blobLen;
while (bytesRemaining > 0) {
int read = fis.read(buf);
if (read < 0) {
throw new IOException("Premature end of BLOB file stream for " +
blobFile.getAbsolutePath());
}
outputStream.write(buf, 0, read);
bytesRemaining -= read;
}
}
} finally {
readLock.unlock();
}
// on successful transfer, delete transient files
int result = inputStream.read();
if (result < 0) {
throw new EOFException("Premature end of GET request");
} else if (blobKey instanceof TransientBlobKey && result == RETURN_OKAY) {
// ignore the result from the operation
if (!blobServer.deleteInternal(jobId, (TransientBlobKey) blobKey)) {
LOG.warn("DELETE operation failed for BLOB {}/{} from {}.", jobId,
blobKey, clientSocket.getInetAddress());
}
}
} catch (SocketException e) {
// happens when the other side disconnects
LOG.debug("Socket connection closed", e);
} catch (Throwable t) {
LOG.error("GET operation failed", t);
clientSocket.close();
}
}
private void put(InputStream inputStream, OutputStream outputStream, byte[] buf) throws IOException {
File incomingFile = null;
try {
// read HEADER contents: job ID, HA mode/permanent or transient BLOB
final int mode = inputStream.read();
if (mode < 0) {
throw new EOFException("Premature end of PUT request");
}
final JobID jobId;
if (mode == JOB_UNRELATED_CONTENT) {
jobId = null;
} else if (mode == JOB_RELATED_CONTENT) {
byte[] jidBytes = new byte[JobID.SIZE];
readFully(inputStream, jidBytes, 0, JobID.SIZE, "JobID");
jobId = JobID.fromByteArray(jidBytes);
} else {
throw new IOException("Unknown type of BLOB addressing.");
}
final BlobKey.BlobType blobType;
{
final int read = inputStream.read();
if (read < 0) {
throw new EOFException("Read an incomplete BLOB type");
} else if (read == TRANSIENT_BLOB.ordinal()) {
blobType = TRANSIENT_BLOB;
} else if (read == PERMANENT_BLOB.ordinal()) {
blobType = PERMANENT_BLOB;
checkArgument(jobId != null, "Invalid BLOB addressing for permanent BLOBs");
} else {
throw new IOException("Invalid data received for the BLOB type: " + read);
}
}
if (LOG.isDebugEnabled()) {
LOG.debug("Received PUT request for BLOB of job {} with from {}.", jobId,
clientSocket.getInetAddress());
}
incomingFile = blobServer.createTemporaryFilename();
byte[] digest = readFileFully(inputStream, incomingFile, buf);
BlobKey blobKey = blobServer.moveTempFileToStore(incomingFile, jobId, digest, blobType);
// Return computed key to client for validation
outputStream.write(RETURN_OKAY);
blobKey.writeToOutputStream(outputStream);
}
catch (SocketException e) {
// happens when the other side disconnects
LOG.debug("Socket connection closed", e);
}
catch (Throwable t) {
LOG.error("PUT operation failed", t);
try {
writeErrorToStream(outputStream, t);
}
catch (IOException e) {
// since we are in an exception case, it means not much that we could not send the error
// ignore this
}
clientSocket.close();
}
finally {
if (incomingFile != null) {
if (!incomingFile.delete() && incomingFile.exists()) {
LOG.warn("Cannot delete BLOB server staging file " + incomingFile.getAbsolutePath());
}
}
}
}
private static byte[] readFileFully(
final InputStream inputStream, final File incomingFile, final byte[] buf)
throws IOException {
MessageDigest md = BlobUtils.createMessageDigest();
try (FileOutputStream fos = new FileOutputStream(incomingFile)) {
while (true) {
final int bytesExpected = readLength(inputStream);
if (bytesExpected == -1) {
// done
break;
}
if (bytesExpected > BUFFER_SIZE) {
throw new IOException(
"Unexpected number of incoming bytes: " + bytesExpected);
}
readFully(inputStream, buf, 0, bytesExpected, "buffer");
fos.write(buf, 0, bytesExpected);
md.update(buf, 0, bytesExpected);
}
return md.digest();
}
}
// --------------------------------------------------------------------------------------------
// Utilities
// --------------------------------------------------------------------------------------------
private static void writeErrorToStream(OutputStream out, Throwable t) throws IOException {
byte[] bytes = InstantiationUtil.serializeObject(t);
out.write(RETURN_ERROR);
writeLength(bytes.length, out);
out.write(bytes);
}
}- BlobServerConnection继承了Thread，它的构造器接收clientSocket及blobServer；它覆盖了Thread的run方法，该方法首先从clientSocket读取请求的operation，如果是PUT_OPERATION则调用put方法，如果是GET_OPERATION则调用get方法
- put方法从inputStream读取jobId及blobType，之后创建incomingFile，将输入的文件先存储到临时文件，然后调用blobServer.moveTempFileToStore方法存储到blob server
- get方法从inputStream读取jobId及blobType，之后调用blobServer.getStorageLocation获取blobFile，之后将其拷贝到local store，然后写入到outputStream
小结
- BlobServer继承了Thread，同时实现了BlobService、BlobWriter、PermanentBlobService、TransientBlobService接口；其构造器使用DefaultServerSocketFactory创建了ServerSocket，同时使用ShutdownHookUtil.addShutdownHook注册了shutdownHook，在shutdown的时候会调用close方法
- BlobServer重写了Thread的run方法，该方法在没有接收到shutdown请求的时候，会不断循环等待serverSocket.accept()，然后创建BlobServerConnection，如果当前activeConnections超过了maxConnections则会不断循环等待2000毫秒，之后将连接维护到activeConnections，然后调用conn.start()
- BlobServerConnection继承了Thread，它的构造器接收clientSocket及blobServer；它覆盖了Thread的run方法，该方法首先从clientSocket读取请求的operation，如果是PUT_OPERATION则调用put方法，如果是GET_OPERATION则调用get方法；put方法从inputStream读取jobId及blobType，之后创建incomingFile，将输入的文件先存储到临时文件，然后调用blobServer.moveTempFileToStore方法存储到blob server；get方法从inputStream读取jobId及blobType，之后调用blobServer.getStorageLocation获取blobFile，之后将其拷贝到local store，然后写入到outputStream
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