Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/3522#discussion_r108714224
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/state/filesystem/AbstractFileStateBackend.java
---
@@ -0,0 +1,556 @@
+/*
+ * 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.state.filesystem;
+
+import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.api.common.JobID;
+import org.apache.flink.configuration.ConfigConstants;
+import org.apache.flink.configuration.ConfigOption;
+import org.apache.flink.configuration.ConfigOptions;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.configuration.IllegalConfigurationException;
+import org.apache.flink.core.fs.FileStatus;
+import org.apache.flink.core.fs.FileSystem;
+import org.apache.flink.core.fs.Path;
+import org.apache.flink.runtime.state.AbstractStateBackend;
+import org.apache.flink.runtime.state.CheckpointMetadataStreamFactory;
+import org.apache.flink.runtime.state.StateBackendGlobalHooks;
+import org.apache.flink.runtime.state.StreamStateHandle;
+import org.apache.flink.util.FileUtils;
+import org.apache.flink.util.FlinkException;
+import org.apache.flink.util.FlinkRuntimeException;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.annotation.Nullable;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.net.URI;
+import java.net.URISyntaxException;
+
+import static org.apache.flink.util.Preconditions.checkArgument;
+import static org.apache.flink.util.Preconditions.checkNotNull;
+
+/**
+ * A base class for all state backends that store their metadata (and
data) in files.
+ * Examples that inherit from this are the {@link FsStateBackend}, the
+ * {@link org.apache.flink.runtime.state.memory.MemoryStateBackend
MemoryStateBackend}, or the
+ * {@code RocksDBStateBackend}.
+ *
+ * <p>This class takes the base checkpoint- and savepoint directory paths,
but also accepts null
+ * for both of then, in which case creating externalized checkpoint is not
possible, and it is not
+ * possible to create a savepoint with a default path. Null is accepted to
enable implementations
+ * that only optionally support default savepoints and externalized
checkpoints.
+ *
+ * <h1>Checkpoint Layout</h1>
+ *
+ * The state backend is configured with a base directory and persists the
checkpoint data of specific
+ * checkpoints in specific subdirectories. For example, if the base
directory was set to
+ * {@code hdfs://namenode:port/flink-checkpoints/}, the state backend will
create a subdirectory with
+ * the job's ID that will contain the actual checkpoints:
+ * ({@code
hdfs://namenode:port/flink-checkpoints/1b080b6e710aabbef8993ab18c6de98b})
+ *
+ * <p>Each checkpoint individually will store all its files in a
subdirectory that includes the
+ * checkpoint number, such as {@code
hdfs://namenode:port/flink-checkpoints/1b080b6e710aabbef8993ab18c6de98b/chk-17/}.
+ *
+ * <h1>Savepoint Layout</h1>
+ *
+ * A savepoint that is set to be stored in path {@code
hdfs://namenode:port/flink-savepoints/}, will create
+ * a subdirectory {@code savepoint-jobId(0, 6)-randomDigits} in which it
stores all savepoint data.
+ * The random digits are added as "entropy" to avoid directory collisions.
+ */
+@PublicEvolving
+public abstract class AbstractFileStateBackend extends
AbstractStateBackend implements StateBackendGlobalHooks {
+
+ private static final long serialVersionUID = 1L;
+
+ private static final Logger LOG =
LoggerFactory.getLogger(AbstractFileStateBackend.class);
+
+ //
------------------------------------------------------------------------
+ // Configuration
+ //
------------------------------------------------------------------------
+
+ /**
+ * The configuration parameter for the checkpoint path/directory.
+ */
+ public static final ConfigOption<String> CHECKPOINT_PATH = ConfigOptions
+ .key(ConfigConstants.CHECKPOINTS_DIRECTORY_KEY)
+ .noDefaultValue()
+ .withDeprecatedKeys("state.backend.fs.checkpointdir");
+
+ /**
+ * The configuration parameter for the savepoint path/directory.
+ */
+ public static final ConfigOption<String> SAVEPOINT_PATH = ConfigOptions
+ .key(ConfigConstants.SAVEPOINT_DIRECTORY_KEY)
+ .noDefaultValue()
+ .withDeprecatedKeys("state.backend.fs.savepointdir");
+
+ //
------------------------------------------------------------------------
+ // Constants
+ //
------------------------------------------------------------------------
+
+ /** The name of the metadata files in checkpoints / savepoints. */
+ public static final String METADATA_FILE_NAME = "_metadata";
+
+ /** The prefix of the checkpoint directory names */
+ public static final String CHECKPOINT_DIR_PREFIX = "chk-";
+
+ //
------------------------------------------------------------------------
+ // State Backend Properties
+ //
------------------------------------------------------------------------
+
+ /** The path where checkpoints will be stored, or null, if none has
been configured */
+ @Nullable
+ private final Path baseCheckpointPath;
+
+ /** The path where savepoints will be stored, or null, if none has been
configured */
+ @Nullable
+ private final Path baseSavepointPath;
+
+ /**
+ * Creates a backend with the given optional checkpoint- and savepoint
base directories.
+ *
+ * @param baseCheckpointPath The base directory for checkpoints, or
null, if none is configured.
+ * @param baseSavepointPath The default directory for savepoints, or
null, if none is set.
+ */
+ protected AbstractFileStateBackend(
+ @Nullable Path baseCheckpointPath,
+ @Nullable Path baseSavepointPath) {
+
+ this(baseCheckpointPath == null ? null :
baseCheckpointPath.toUri(),
+ baseSavepointPath == null ? null :
baseSavepointPath.toUri());
+ }
+
+ /**
+ * Creates a backend with the given optional checkpoint- and savepoint
base directories.
+ *
+ * @param baseCheckpointPath The base directory for checkpoints, or
null, if none is configured.
+ * @param baseSavepointPath The default directory for savepoints, or
null, if none is set.
+ */
+ protected AbstractFileStateBackend(
+ @Nullable URI baseCheckpointPath,
+ @Nullable URI baseSavepointPath) {
+
+ this.baseCheckpointPath = baseCheckpointPath == null ? null :
validateAndNormalizeUri(baseCheckpointPath);
+ this.baseSavepointPath = baseSavepointPath == null ? null :
validateAndNormalizeUri(baseSavepointPath);
+ }
+
+ /**
+ * Creates a new backend using the given checkpoint-/savepoint
directories, or the values defined in
+ * the given configuration. If a checkpoint-/savepoint parameter is not
null, that value takes precedence
+ * over the value in the configuration. If the configuration does not
specify a value, it is possible
+ * that the checkpoint-/savepoint directories in the backend will be
null.
+ *
+ * <p>This constructor can be used to create a backend that is based
partially on a given backend
+ * and partially on a configuration.
+ *
+ * @param baseCheckpointPath The checkpoint base directory to use (or
null).
+ * @param baseSavepointPath The default savepoint directory to use (or
null).
+ * @param configuration The configuration to read values from
+ */
+ protected AbstractFileStateBackend(
+ @Nullable Path baseCheckpointPath,
+ @Nullable Path baseSavepointPath,
+ Configuration configuration) {
+
+ this(parameterOrConfigured(baseCheckpointPath, configuration,
CHECKPOINT_PATH),
+ parameterOrConfigured(baseSavepointPath,
configuration, SAVEPOINT_PATH));
+ }
+
+ //
------------------------------------------------------------------------
+
+ /**
+ * Gets the checkpoint base directory. Jobs will create job-specific
subdirectories
+ * for checkpoints within this directory. May be null, if not
configured.
+ *
+ * @return The checkpoint base directory
+ */
+ @Nullable
+ public Path getCheckpointPath() {
+ return baseCheckpointPath;
+ }
+
+ /**
+ * Gets the directory where savepoints are stored by default (when no
custom path is given
+ * to the savepoint trigger command).
+ *
+ * @return The default directory for savepoints, or null, if no default
directory has been configured.
+ */
+ @Nullable
+ public Path getSavepointPath() {
+ return baseSavepointPath;
+ }
+
+ //
------------------------------------------------------------------------
+ // Metadata Persistence
+ //
------------------------------------------------------------------------
+
+ /**
+ * Checks whether this backend supports externalized checkpoints, which
is the case when
+ * a checkpoint base directory is configured.
+ */
+ @Override
+ public boolean supportsExternalizedMetadata() {
+ return baseCheckpointPath != null;
+ }
+
+ @Nullable
+ @Override
+ public String getMetadataPersistenceLocation() {
+ return baseCheckpointPath == null ? null :
baseCheckpointPath.toString();
+ }
+
+ @Override
+ public StreamStateHandle resolveCheckpointLocation(String
checkpointPath) throws IOException {
+ checkNotNull(checkpointPath, "checkpointPath");
+ checkArgument(!checkpointPath.isEmpty(), "empty checkpoint
path");
+
+ // we resolve without strictly validating the metadata file, to
resume from cases
+ // where a differently named metadata file was written (as in
prior Flink version)
+ final FileStatus metadataFileStatus =
resolveCheckpointPointer(checkpointPath, false);
+ return new FileStateHandle(metadataFileStatus.getPath(),
metadataFileStatus.getLen());
+ }
+
+ @Override
+ public CheckpointMetadataStreamFactory
createCheckpointMetadataStreamFactory(
+ JobID jobID,
+ long checkpointId) throws IOException {
+
+ checkNotNull(jobID, "jobID");
+
+ final Path checkpointBaseDir =
getCheckpointDirectoryForJob(jobID);
+ final Path checkpointDir =
createSpecificCheckpointPath(checkpointBaseDir, checkpointId);
+ final Path metadataFilePath = new Path(checkpointDir,
METADATA_FILE_NAME);
+
+ return new
FsCheckpointMetadataStreamFactory(checkpointDir.getFileSystem(), checkpointDir,
metadataFilePath);
+ }
+
+ @Override
+ public CheckpointMetadataStreamFactory
createSavepointMetadataStreamFactory(
+ JobID jobID,
+ @Nullable String targetLocation) throws IOException {
+
+ // the directory inside which we create the savepoint
+ final Path basePath;
+
+ if (targetLocation != null) {
+ try {
+ basePath = new Path(targetLocation);
+ }
+ catch (IllegalArgumentException e) {
+ throw new IOException("Cannot initialize
savepoint to '" + targetLocation +
+ "' because it is not a valid
file path.");
+ }
+ }
+ else if (baseSavepointPath != null) {
+ basePath = baseSavepointPath;
+ }
+ else {
+ throw new UnsupportedOperationException(
+ "Cannot perform a savepoint without a
target location when no default savepoint directory " +
+ "has been configured
via '" + SAVEPOINT_PATH.key() + "'.");
+ }
+
+ final FileSystem fs = basePath.getFileSystem();
+ final Path savepointDir = initializeSavepointDirectory(fs,
basePath, jobID);
+ final Path metadataFilePath = new Path(savepointDir,
METADATA_FILE_NAME);
+
+ return new FsCheckpointMetadataStreamFactory(fs, savepointDir,
metadataFilePath);
+ }
+
+ //
------------------------------------------------------------------------
+ // Global Hooks
+ //
------------------------------------------------------------------------
+
+ @Override
+ public void disposeSavepoint(String pointer) throws IOException {
+ checkNotNull(pointer, "pointer");
+
+ // to be save, we make sure we call this to verify that the
metadata file exists
+ // in the pointed directory, or that this points to the
metadata file directly
+ final FileStatus metadataFileStatus =
resolveCheckpointPointer(pointer, true);
+
+ final Path savepointDir =
metadataFileStatus.getPath().getParent();
+ final FileSystem fs = savepointDir.getFileSystem();
+ fs.delete(savepointDir, true);
+ }
+
+ //
------------------------------------------------------------------------
+ // Paths
+ //
------------------------------------------------------------------------
+
+ /**
+ * Builds directory into which a specific job checkpoints, meaning the
directory inside which
+ * it creates the checkpoint-specific subdirectories.
+ *
+ * <p>This method only succeeds if a base checkpoint directory has been
set; otherwise
+ * the method fails with an exception.
+ *
+ * @param jobId The ID of the job
+ * @return The job's checkpoint directory, re
+ *
+ * @throws UnsupportedOperationException Thrown, if no base checkpoint
directory has been set.
+ */
+ protected Path getCheckpointDirectoryForJob(JobID jobId) {
+ if (baseCheckpointPath != null) {
+ return new Path(baseCheckpointPath, jobId.toString());
+ }
+ else {
+ throw new UnsupportedOperationException(
+ "Cannot write checkpoint data when no
checkpoint directory has been configured via '" +
+ CHECKPOINT_PATH.key() +
"'.");
+ }
+ }
+
+ /**
+ * Creates the directory path for a specific checkpoint of a job.
+ *
+ * @param jobCheckpointDir The directory into which the job checkpoints
+ * @param checkpointId The ID (logical timestamp) of the checkpoint
+ *
+ * @return The checkpoint directory path.
+ */
+ protected static Path createSpecificCheckpointPath(Path
jobCheckpointDir, long checkpointId) {
+ return new Path(jobCheckpointDir, CHECKPOINT_DIR_PREFIX +
checkpointId);
+ }
+
+ /**
+ *
+ * <p>Important - if the pointer points directly to a file, this does
not valicate t
+ *
+ * @param checkpointPointer The pointer to resolve
+ * @return The file status of the checkpoint/savepoint's metadata file.
+ *
+ * @throws IOException Thrown, if the pointer cannot be resolved, the
file system not accessed, or
+ * the pointer points to a location that does not
seem to be a checkpoint/savepoint.
+ */
+ protected static FileStatus resolveCheckpointPointer(
+ String checkpointPointer,
+ boolean validateMetadataFileName) throws IOException {
+
+ // check if the pointer is in fact a valid file path
+ final Path path;
+ try {
+ path = new Path(checkpointPointer);
+ }
+ catch (Exception e) {
+ throw new IOException("Checkpoint/savepoint path '" +
checkpointPointer + "' is not a valid file URI");
+ }
+
+ // check if the file system can be accessed
+ final FileSystem fs;
+ try {
+ fs = path.getFileSystem();
+ }
+ catch (IOException e) {
+ throw new IOException("Cannot access file system for
checkpoint/savepoint path '" +
+ checkpointPointer + "'.");
--- End diff --
Maybe we could add `e` as the cause.
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