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本文主要研究一下 flink 的 BlobStoreService
BlobView
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/blob/BlobView.java
public interface BlobView {
/**
* Copies a blob to a local file.
*
* @param jobId ID of the job this blob belongs to (or <tt>null</tt> if job-unrelated)
* @param blobKey The blob ID
* @param localFile The local file to copy to
*
* @return whether the file was copied (<tt>true</tt>) or not (<tt>false</tt>)
* @throws IOException If the copy fails
*/
boolean get(JobID jobId, BlobKey blobKey, File localFile) throws IOException;
}
BlobView 定义了 get 方法，将指定的 blob 拷贝到 localFile
BlobStore
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/blob/BlobStore.java
public interface BlobStore extends BlobView {
/**
* Copies the local file to the blob store.
*
* @param localFile The file to copy
* @param jobId ID of the job this blob belongs to (or <tt>null</tt> if job-unrelated)
* @param blobKey The ID for the file in the blob store
*
* @return whether the file was copied (<tt>true</tt>) or not (<tt>false</tt>)
* @throws IOException If the copy fails
*/
boolean put(File localFile, JobID jobId, BlobKey blobKey) throws IOException;
/**
* Tries to delete a blob from storage.
*
* <p>NOTE: This also tries to delete any created directories if empty.</p>
*
* @param jobId ID of the job this blob belongs to (or <tt>null</tt> if job-unrelated)
* @param blobKey The blob ID
*
* @return <tt>true</tt> if the given blob is successfully deleted or non-existing;
* <tt>false</tt> otherwise
*/
boolean delete(JobID jobId, BlobKey blobKey);
/**
* Tries to delete all blobs for the given job from storage.
*
* <p>NOTE: This also tries to delete any created directories if empty.</p>
*
* @param jobId The JobID part of all blobs to delete
*
* @return <tt>true</tt> if the job directory is successfully deleted or non-existing;
* <tt>false</tt> otherwise
*/
boolean deleteAll(JobID jobId);
}
BlobStore 继承了 BlobView，它定义了 put、delete、deleteAll 方法
BlobStoreService
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/blob/BlobStoreService.java
public interface BlobStoreService extends BlobStore, Closeable {
/**
* Closes and cleans up the store. This entails the deletion of all blobs.
*/
void closeAndCleanupAllData();
}
BlobStoreService 继承了 BlobStore 及 Closeable 接口，它定义了 closeAndCleanupAllData 方法；它有两个实现类，分别是 VoidBlobStore、FileSystemBlobStore
VoidBlobStore
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/blob/VoidBlobStore.java
public class VoidBlobStore implements BlobStoreService {
@Override
public boolean put(File localFile, JobID jobId, BlobKey blobKey) throws IOException {
return false;
}
@Override
public boolean get(JobID jobId, BlobKey blobKey, File localFile) throws IOException {
return false;
}
@Override
public boolean delete(JobID jobId, BlobKey blobKey) {
return true;
}
@Override
public boolean deleteAll(JobID jobId) {
return true;
}
@Override
public void closeAndCleanupAllData() {}
@Override
public void close() throws IOException {}
}
VoidBlobStore 实现了 BlobStoreService 接口，它执行空操作
FileSystemBlobStore
flink-release-1.7.2/flink-runtime/src/main/java/org/apache/flink/runtime/blob/FileSystemBlobStore.java
public class FileSystemBlobStore implements BlobStoreService {
private static final Logger LOG = LoggerFactory.getLogger(FileSystemBlobStore.class);
/** The file system in which blobs are stored. */
private final FileSystem fileSystem;
/** The base path of the blob store. */
private final String basePath;
public FileSystemBlobStore(FileSystem fileSystem, String storagePath) throws IOException {
this.fileSystem = checkNotNull(fileSystem);
this.basePath = checkNotNull(storagePath) + “/blob”;
LOG.info(“Creating highly available BLOB storage directory at {}”, basePath);
fileSystem.mkdirs(new Path(basePath));
LOG.debug(“Created highly available BLOB storage directory at {}”, basePath);
}
// – Put ——————————————————————
@Override
public boolean put(File localFile, JobID jobId, BlobKey blobKey) throws IOException {
return put(localFile, BlobUtils.getStorageLocationPath(basePath, jobId, blobKey));
}
private boolean put(File fromFile, String toBlobPath) throws IOException {
try (OutputStream os = fileSystem.create(new Path(toBlobPath), FileSystem.WriteMode.OVERWRITE)) {
LOG.debug(“Copying from {} to {}.”, fromFile, toBlobPath);
Files.copy(fromFile, os);
}
return true;
}
// – Get ——————————————————————
@Override
public boolean get(JobID jobId, BlobKey blobKey, File localFile) throws IOException {
return get(BlobUtils.getStorageLocationPath(basePath, jobId, blobKey), localFile, blobKey);
}
private boolean get(String fromBlobPath, File toFile, BlobKey blobKey) throws IOException {
checkNotNull(fromBlobPath, “Blob path”);
checkNotNull(toFile, “File”);
checkNotNull(blobKey, “Blob key”);
if (!toFile.exists() && !toFile.createNewFile()) {
throw new IOException(“Failed to create target file to copy to”);
}
final Path fromPath = new Path(fromBlobPath);
MessageDigest md = BlobUtils.createMessageDigest();
final int buffSize = 4096; // like IOUtils#BLOCKSIZE, for chunked file copying
boolean success = false;
try (InputStream is = fileSystem.open(fromPath);
FileOutputStream fos = new FileOutputStream(toFile)) {
LOG.debug(“Copying from {} to {}.”, fromBlobPath, toFile);
// not using IOUtils.copyBytes(is, fos) here to be able to create a hash on-the-fly
final byte[] buf = new byte[buffSize];
int bytesRead = is.read(buf);
while (bytesRead >= 0) {
fos.write(buf, 0, bytesRead);
md.update(buf, 0, bytesRead);
bytesRead = is.read(buf);
}
// verify that file contents are correct
final byte[] computedKey = md.digest();
if (!Arrays.equals(computedKey, blobKey.getHash())) {
throw new IOException(“Detected data corruption during transfer”);
}
success = true;
} finally {
// if the copy fails, we need to remove the target file because
// outside code relies on a correct file as long as it exists
if (!success) {
try {
toFile.delete();
} catch (Throwable ignored) {}
}
}
return true; // success is always true here
}
// – Delete —————————————————————
@Override
public boolean delete(JobID jobId, BlobKey blobKey) {
return delete(BlobUtils.getStorageLocationPath(basePath, jobId, blobKey));
}
@Override
public boolean deleteAll(JobID jobId) {
return delete(BlobUtils.getStorageLocationPath(basePath, jobId));
}
private boolean delete(String blobPath) {
try {
LOG.debug(“Deleting {}.”, blobPath);
Path path = new Path(blobPath);
boolean result = fileSystem.delete(path, true);
// send a call to delete the directory containing the file. This will
// fail (and be ignored) when some files still exist.
try {
fileSystem.delete(path.getParent(), false);
fileSystem.delete(new Path(basePath), false);
} catch (IOException ignored) {}
return result;
}
catch (Exception e) {
LOG.warn(“Failed to delete blob at ” + blobPath);
return false;
}
}
@Override
public void closeAndCleanupAllData() {
try {
LOG.debug(“Cleaning up {}.”, basePath);
fileSystem.delete(new Path(basePath), true);
}
catch (Exception e) {
LOG.error(“Failed to clean up recovery directory.”, e);
}
}
@Override
public void close() throws IOException {
// nothing to do for the FileSystemBlobStore
}
}
FileSystemBlobStore 实现了 BlobStoreService，它的构造器要求传入 fileSystem 及 storagePath；put 方法通过 fileSystem.create 来创建目标 OutputStream，然后通过 Files.copy 把 localFile 拷贝到 toBlobPath；get 方法通过 fileSystem.open 打开要读取的 blob，然后写入到 localFile；delete 及 deleteAll 方法通过 BlobUtils.getStorageLocationPath 获取 blobPath，然后调用 fileSystem.delete 来删除；closeAndCleanupAllData 方法直接调用 fileSystem.delete 来递归删除整个 storagePath
小结
BlobView 定义了 get 方法，将指定的 blob 拷贝到 localFile；BlobStore 继承了 BlobView，它定义了 put、delete、deleteAll 方法
BlobStoreService 继承了 BlobStore 及 Closeable 接口，它定义了 closeAndCleanupAllData 方法；它有两个实现类，分别是 VoidBlobStore、FileSystemBlobStore
VoidBlobStore 实现了 BlobStoreService 接口，它执行空操作；FileSystemBlobStore 实现了 BlobStoreService，它的构造器要求传入 fileSystem 及 storagePath；put 方法通过 fileSystem.create 来创建目标 OutputStream，然后通过 Files.copy 把 localFile 拷贝到 toBlobPath；get 方法通过 fileSystem.open 打开要读取的 blob，然后写入到 localFile；delete 及 deleteAll 方法通过 BlobUtils.getStorageLocationPath 获取 blobPath，然后调用 fileSystem.delete 来删除；closeAndCleanupAllData 方法直接调用 fileSystem.delete 来递归删除整个 storagePath
doc
BlobStoreService