com.sap.hana.datalake.files.committers.manifest.ManifestStoreOperationsThroughFileSystem Maven / Gradle / Ivy

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An implementation of org.apache.hadoop.fs.FileSystem targeting SAP HANA Data Lake Files.
There is a newer version: 3.0.27
/*
 * 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 com.sap.hana.datalake.files.committers.manifest;

import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.CommonPathCapabilities;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.RemoteIterator;
import com.sap.hana.datalake.files.shaded.org.apache.hadoop.util.JsonSerialization;

/**
 * Implementation of manifest store operations through the filesystem API.
 * This class is subclassed in the ABFS module, which does add the resilient
 * commit method.
 */
@InterfaceAudience.LimitedPrivate("mapreduce, object-stores")
@InterfaceStability.Unstable
class ManifestStoreOperationsThroughFileSystem extends ManifestStoreOperations {

    /**
     * Are etags guaranteed to be preserved across rename() operations.
     * FileSystems MUST NOT declare support for this feature
     * unless this holds.
     *
     * Only available in {@link CommonPathCapabilities} from Hadoop 3.3.2.
     */
    public static final String COMMON_PATH_CAPABILITY_ETAGS_PRESERVED_IN_RENAME = "fs.capability.etags.preserved.in.rename";

    /**
     * Filesystem; set in {@link #bindToFileSystem(FileSystem, Path)}.
     */
    private FileSystem fileSystem;

    /**
     * Has a call to FileSystem.msync() failed as unsupported?
     * If so, no new attempts will be made when
     * (@link {@link #msync(Path)} is invoked.
     */
    private boolean msyncUnsupported = false;

    /**
     * Direct Constructor.
     * @param fileSystem filesystem to write through.
     */
    public ManifestStoreOperationsThroughFileSystem(final FileSystem fileSystem) {
        this.fileSystem = fileSystem;
    }

    /**
     * Constructor used for introspection-based binding.
     */
    public ManifestStoreOperationsThroughFileSystem() {
    }

    @Override
    public void close() throws IOException {
        /* no-op; FS is assumed to be shared. */

    }

    /**
     * Get the filesystem.
     * @return the filesystem; null until bound.
     */
    public FileSystem getFileSystem() {
        return fileSystem;
    }

    @Override
    public void bindToFileSystem(FileSystem filesystem, Path path) throws IOException {
        fileSystem = filesystem;
    }

    @Override
    public FileStatus getFileStatus(Path path) throws IOException {
        return fileSystem.getFileStatus(path);
    }

    /**
     * Using FileSystem.isFile to offer stores the option to optimize their probes.
     * @param path path to probe
     * @return true if the path resolves to a file.
     * @throws IOException IO failure.
     */
    @SuppressWarnings("deprecation")
    @Override
    public boolean isFile(Path path) throws IOException {
        return fileSystem.isFile(path);
    }

    @Override
    public boolean delete(Path path, boolean recursive)
            throws IOException {
        return fileSystem.delete(path, recursive);
    }

    @Override
    public boolean mkdirs(Path path)
            throws IOException {
        return fileSystem.mkdirs(path);
    }

    @Override
    public boolean renameFile(Path source, Path dest)
            throws IOException {
        return fileSystem.rename(source, dest);
    }

    @Override
    public RemoteIterator listStatusIterator(Path path)
            throws IOException {
        return fileSystem.listStatusIterator(path);
    }

    @Override
    public TaskManifest loadTaskManifest(
            JsonSerialization serializer,
            FileStatus st) throws IOException {
        return TaskManifest.load(serializer, fileSystem, st.getPath(), st);
    }

    @Override
    public > void save(
            final T manifestData,
            final Path path,
            final boolean overwrite) throws IOException {
        manifestData.save(fileSystem, path, overwrite);
    }

    /**
     * Probe filesystem capabilities.
     * @param path path to probe.
     * @return true if the FS declares its renames work.
     */
    @Override
    public boolean storePreservesEtagsThroughRenames(Path path) {
        try {
            return fileSystem.hasPathCapability(path, COMMON_PATH_CAPABILITY_ETAGS_PRESERVED_IN_RENAME);
        } catch (IOException ignored) {
            return false;
        }
    }

    /**
     * Invokes FileSystem msync(); swallows UnsupportedOperationExceptions.
     * This ensures client metadata caches are in sync in an HDFS-HA deployment.
     * No other filesystems support this; in the absence of a hasPathCapability()
     * probe, after the operation is rejected, an atomic boolean is set
     * to stop further attempts from even trying.
     * @param path path
     * @throws IOException failure to synchronize.
     */
    @Override
    public void msync(Path path) throws IOException {
        // there's need for atomicity here, as the sole cost of
        // multiple failures
        if (msyncUnsupported) {
            return;
        }
        // qualify so we can be confident that the FS being synced
        // is the one we expect.
        fileSystem.makeQualified(path);
        try {
            fileSystem.msync();
        } catch (UnsupportedOperationException ignored) {
            // this exception is the default.
            // set the unsupported flag so no future attempts are made.
            msyncUnsupported = true;
        }
    }

}