/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.runtime.blob;
import org.apache.flink.configuration.BlobServerOptions;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.util.FileUtils;
import org.apache.flink.util.IOUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.URL;
import java.util.concurrent.atomic.AtomicBoolean;
import static org.apache.flink.util.Preconditions.checkArgument;
import static org.apache.flink.util.Preconditions.checkNotNull;
/**
* The BLOB cache implements a local cache for content-addressable BLOBs.
*
* <p>When requesting BLOBs through the {@link BlobCache#getURL} methods, the
* BLOB cache will first attempt to serve the file from its local cache. Only if
* the local cache does not contain the desired BLOB, the BLOB cache will try to
* download it from a distributed file system (if available) or the BLOB
* server.</p>
*/
public final class BlobCache implements BlobService {
/** The log object used for debugging. */
private static final Logger LOG = LoggerFactory.getLogger(BlobCache.class);
private final InetSocketAddress serverAddress;
/** Root directory for local file storage */
private final File storageDir;
/** Blob store for distributed file storage, e.g. in HA */
private final BlobView blobView;
private final AtomicBoolean shutdownRequested = new AtomicBoolean();
/** Shutdown hook thread to ensure deletion of the storage directory. */
private final Thread shutdownHook;
/** The number of retries when the transfer fails */
private final int numFetchRetries;
/** Configuration for the blob client like ssl parameters required to connect to the blob server */
private final Configuration blobClientConfig;
/**
* Instantiates a new BLOB cache.
*
* @param serverAddress
* address of the {@link BlobServer} to use for fetching files from
* @param blobClientConfig
* global configuration
* @param blobView
* (distributed) blob store file system to retrieve files from first
*
* @throws IOException
* thrown if the (local or distributed) file storage cannot be created or is not usable
*/
public BlobCache(
final InetSocketAddress serverAddress,
final Configuration blobClientConfig,
final BlobView blobView) throws IOException {
this.serverAddress = checkNotNull(serverAddress);
this.blobClientConfig = checkNotNull(blobClientConfig);
this.blobView = checkNotNull(blobView, "blobStore");
// configure and create the storage directory
String storageDirectory = blobClientConfig.getString(BlobServerOptions.STORAGE_DIRECTORY);
this.storageDir = BlobUtils.initStorageDirectory(storageDirectory);
LOG.info("Created BLOB cache storage directory " + storageDir);
// configure the number of fetch retries
final int fetchRetries = blobClientConfig.getInteger(BlobServerOptions.FETCH_RETRIES);
if (fetchRetries >= 0) {
this.numFetchRetries = fetchRetries;
}
else {
LOG.warn("Invalid value for {}. System will attempt no retires on failed fetches of BLOBs.",
BlobServerOptions.FETCH_RETRIES.key());
this.numFetchRetries = 0;
}
// Add shutdown hook to delete storage directory
shutdownHook = BlobUtils.addShutdownHook(this, LOG);
}
/**
* Returns the URL for the BLOB with the given key. The method will first attempt to serve
* the BLOB from its local cache. If the BLOB is not in the cache, the method will try to download it
* from this cache's BLOB server.
*
* @param requiredBlob The key of the desired BLOB.
* @return URL referring to the local storage location of the BLOB.
* @throws IOException Thrown if an I/O error occurs while downloading the BLOBs from the BLOB server.
*/
public URL getURL(final BlobKey requiredBlob) throws IOException {
checkArgument(requiredBlob != null, "BLOB key cannot be null.");
final File localJarFile = BlobUtils.getStorageLocation(storageDir, requiredBlob);
if (localJarFile.exists()) {
return localJarFile.toURI().toURL();
}
// first try the distributed blob store (if available)
try {
blobView.get(requiredBlob, localJarFile);
} catch (Exception e) {
LOG.info("Failed to copy from blob store. Downloading from BLOB server instead.", e);
}
if (localJarFile.exists()) {
return localJarFile.toURI().toURL();
}
// fallback: download from the BlobServer
final byte[] buf = new byte[BlobServerProtocol.BUFFER_SIZE];
// loop over retries
int attempt = 0;
while (true) {
if (attempt == 0) {
LOG.info("Downloading {} from {}", requiredBlob, serverAddress);
} else {
LOG.info("Downloading {} from {} (retry {})", requiredBlob, serverAddress, attempt);
}
try {
BlobClient bc = null;
InputStream is = null;
OutputStream os = null;
try {
bc = new BlobClient(serverAddress, blobClientConfig);
is = bc.get(requiredBlob);
os = new FileOutputStream(localJarFile);
while (true) {
final int read = is.read(buf);
if (read < 0) {
break;
}
os.write(buf, 0, read);
}
// we do explicitly not use a finally block, because we want the closing
// in the regular case to throw exceptions and cause the writing to fail.
// But, the closing on exception should not throw further exceptions and
// let us keep the root exception
os.close();
os = null;
is.close();
is = null;
bc.close();
bc = null;
// success, we finished
return localJarFile.toURI().toURL();
}
catch (Throwable t) {
// we use "catch (Throwable)" to keep the root exception. Otherwise that exception
// it would be replaced by any exception thrown in the finally block
IOUtils.closeQuietly(os);
IOUtils.closeQuietly(is);
IOUtils.closeQuietly(bc);
if (t instanceof IOException) {
throw (IOException) t;
} else {
throw new IOException(t.getMessage(), t);
}
}
}
catch (IOException e) {
String message = "Failed to fetch BLOB " + requiredBlob + " from " + serverAddress +
" and store it under " + localJarFile.getAbsolutePath();
if (attempt < numFetchRetries) {
attempt++;
if (LOG.isDebugEnabled()) {
LOG.debug(message + " Retrying...", e);
} else {
LOG.error(message + " Retrying...");
}
}
else {
LOG.error(message + " No retries left.", e);
throw new IOException(message, e);
}
}
} // end loop over retries
}
/**
* Deletes the file associated with the given key from the BLOB cache.
* @param key referring to the file to be deleted
*/
public void delete(BlobKey key) throws IOException{
final File localFile = BlobUtils.getStorageLocation(storageDir, key);
if (localFile.exists() && !localFile.delete()) {
LOG.warn("Failed to delete locally cached BLOB " + key + " at " + localFile.getAbsolutePath());
}
}
/**
* Deletes the file associated with the given key from the BLOB cache and
* BLOB server.
*
* @param key referring to the file to be deleted
* @throws IOException
* thrown if an I/O error occurs while transferring the request to
* the BLOB server or if the BLOB server cannot delete the file
*/
public void deleteGlobal(BlobKey key) throws IOException {
// delete locally
delete(key);
// then delete on the BLOB server
// (don't use the distributed storage directly - this way the blob
// server is aware of the delete operation, too)
try (BlobClient bc = createClient()) {
bc.delete(key);
}
}
@Override
public int getPort() {
return serverAddress.getPort();
}
@Override
public void close() throws IOException {
if (shutdownRequested.compareAndSet(false, true)) {
LOG.info("Shutting down BlobCache");
// Clean up the storage directory
try {
FileUtils.deleteDirectory(storageDir);
} finally {
// Remove shutdown hook to prevent resource leaks, unless this is invoked by the shutdown hook itself
if (shutdownHook != null && shutdownHook != Thread.currentThread()) {
try {
Runtime.getRuntime().removeShutdownHook(shutdownHook);
} catch (IllegalStateException e) {
// race, JVM is in shutdown already, we can safely ignore this
} catch (Throwable t) {
LOG.warn("Exception while unregistering BLOB cache's cleanup shutdown hook.");
}
}
}
}
}
@Override
public BlobClient createClient() throws IOException {
return new BlobClient(serverAddress, blobClientConfig);
}
public File getStorageDir() {
return this.storageDir;
}
}