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| 1 | +/* |
| 2 | + * Licensed to the Apache Software Foundation (ASF) under one |
| 3 | + * or more contributor license agreements. See the NOTICE file |
| 4 | + * distributed with this work for additional information |
| 5 | + * regarding copyright ownership. The ASF licenses this file |
| 6 | + * to you under the Apache License, Version 2.0 (the |
| 7 | + * "License"); you may not use this file except in compliance |
| 8 | + * with the License. You may obtain a copy of the License at |
| 9 | + * |
| 10 | + * http://www.apache.org/licenses/LICENSE-2.0 |
| 11 | + * |
| 12 | + * Unless required by applicable law or agreed to in writing, software |
| 13 | + * distributed under the License is distributed on an "AS IS" BASIS, |
| 14 | + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 15 | + * See the License for the specific language governing permissions and |
| 16 | + * limitations under the License. |
| 17 | + */ |
| 18 | + |
| 19 | +package org.apache.hadoop.fs.impl; |
| 20 | + |
| 21 | +import java.io.FileNotFoundException; |
| 22 | +import java.io.IOException; |
| 23 | + |
| 24 | +import javax.annotation.Nullable; |
| 25 | + |
| 26 | +import org.apache.hadoop.classification.InterfaceAudience; |
| 27 | +import org.apache.hadoop.classification.InterfaceStability; |
| 28 | +import org.apache.hadoop.fs.FileStatus; |
| 29 | +import org.apache.hadoop.fs.Path; |
| 30 | +import org.apache.hadoop.fs.PathIOException; |
| 31 | +import org.apache.hadoop.fs.statistics.IOStatisticsSource; |
| 32 | + |
| 33 | +/** |
| 34 | + * This is something internal to make our rename-based job committers |
| 35 | + * more resilient to failures. |
| 36 | + * If you are in the hive team: do not use this as it lacks |
| 37 | + * spec, tests, stability, etc. if we find you using it we will change |
| 38 | + * the signature just to stop your code compiling. |
| 39 | + * View this as a proof of concept of the functionality we'd want from a |
| 40 | + * "modern" rename call, but not the API (which would be builder based, |
| 41 | + * return a future, etc). |
| 42 | + */ |
| 43 | +@InterfaceAudience.LimitedPrivate({"Filesystems", "hadoop-mapreduce-client-core"}) |
| 44 | +@InterfaceStability.Unstable |
| 45 | +public interface ResilientCommitByRename { |
| 46 | + |
| 47 | + /** |
| 48 | + * Path capability. |
| 49 | + * FS Instances which support the operation MUST return |
| 50 | + * true and implement the method; FileSystem instances which do not |
| 51 | + * MUST return false. |
| 52 | + * There's a risk wrapper filesystems may pass the probe |
| 53 | + * through. |
| 54 | + * Clients MUST check for both the interface and this |
| 55 | + * cqpability. |
| 56 | + */ |
| 57 | + String RESILIENT_COMMIT_BY_RENAME_PATH_CAPABILITY = |
| 58 | + "org.apache.hadoop.fs.impl.resilient.commit.by.rename"; |
| 59 | + |
| 60 | + /** |
| 61 | + * Rename source file to dest path *Exactly*; no subdirectory games here. |
| 62 | + * if the op does not raise an exception,then |
| 63 | + * the data at dest is the data which was at source. |
| 64 | + * |
| 65 | + * Requirements |
| 66 | + * |
| 67 | + * <pre> |
| 68 | + * exists(FS, source) else raise FileNotFoundException |
| 69 | + * source != dest else raise PathIOException |
| 70 | + * not exists(FS, dest) |
| 71 | + * isDir(FS, dest.getParent) |
| 72 | + * </pre> |
| 73 | + * <ol> |
| 74 | + * <li>supported in this instance else raise PathIOException</li> |
| 75 | + * <li>source != dest else raise PathIOException</li> |
| 76 | + * <li>source must exist else raise FileNotFoundException</li> |
| 77 | + * <li>source must exist and be a file</li> |
| 78 | + * <li>dest must not exist; </li> |
| 79 | + * <li>dest.getParent() must be a dir</li> |
| 80 | + * <li>if sourceEtag is non-empty, it MAY be used to qualify/validate the rename.</li> |
| 81 | + * </ol> |
| 82 | + * |
| 83 | + * The outcome of the operation is undefined if source is not a file, dest exists, |
| 84 | + * dest.getParent() doesn't exist/is a file. |
| 85 | + * That is: implementations SHOULD assume that the code calling this method has |
| 86 | + * set up the destination directory tree and is only invoking this call on a file. |
| 87 | + * Accordingly: <i>implementations MAY skip validation checks</i> |
| 88 | + * |
| 89 | + * If sourceStatus is not null, its contents MAY be used to qualify the rename. |
| 90 | + * <ol> |
| 91 | + * <li>Values extracted from sourceStatus SHALL take priority over |
| 92 | + * sourceEtag/sourceLastModified parameter.</li> |
| 93 | + * <li>sourceStatus.getPath().getName() MUST equal source.getName()</li> |
| 94 | + * <li>If store has a subclass of FileStatus and it is sourceStatus is of this type, |
| 95 | + * custom information MAY be used to qualify/validate the request. |
| 96 | + * This MAY include etag or S3 version ID extraction,</li> |
| 97 | + * </ol> |
| 98 | + * |
| 99 | + * Filesystems MAY support this call on an instance-by-instance basis, depending on |
| 100 | + * the nature of the remote store. |
| 101 | + * If not available the implementation MUST {@code ResilientCommitByRenameUnsupported}. |
| 102 | + * Callers SHOULD use a check of |
| 103 | + * {@code hasPathCapability(source, RESILIENT_COMMIT_BY_RENAME_PATH_CAPABILITY} |
| 104 | + * before trying to use this call. |
| 105 | + * |
| 106 | + * PostConditions on a successful operation: |
| 107 | + * <pre> |
| 108 | + * FS' where: |
| 109 | + * not exists(FS', source) |
| 110 | + * and exists(FS', dest) |
| 111 | + * and data(FS', dest) == data (FS, source) |
| 112 | + * </pre> |
| 113 | + * This is exactly the same outcome as `FileSystem.rename()` when the same preconditions |
| 114 | + * are met. This API call simply restricts the operation to file rename with strict |
| 115 | + * conditions, (no need to be 'clever' about dest path calculation) and the ability |
| 116 | + * to pass in etags, modtimes and file status values. |
| 117 | + * |
| 118 | + * @param source path to source file |
| 119 | + * @param dest destination of rename. |
| 120 | + * @param sourceEtag etag of source file. may be null or empty |
| 121 | + * @param sourceStatus nullable FileStatus of source. |
| 122 | + * @throws FileNotFoundException source file not found |
| 123 | + * @throws ResilientCommitByRenameUnsupported not available on this store. |
| 124 | + * @throws PathIOException failure, including source and dest being the same path |
| 125 | + * @throws IOException any other exception |
| 126 | + */ |
| 127 | + default CommitByRenameOutcome commitSingleFileByRename( |
| 128 | + Path source, |
| 129 | + Path dest, |
| 130 | + @Nullable String sourceEtag, |
| 131 | + @Nullable FileStatus sourceStatus) |
| 132 | + throws FileNotFoundException, |
| 133 | + ResilientCommitByRenameUnsupported, |
| 134 | + PathIOException, |
| 135 | + IOException { |
| 136 | + throw new ResilientCommitByRenameUnsupported(source.toString()); |
| 137 | + } |
| 138 | + |
| 139 | + /** |
| 140 | + * The outcome. This is always a success, but it |
| 141 | + * may include some information about what happened. |
| 142 | + */ |
| 143 | + class CommitByRenameOutcome implements IOStatisticsSource { |
| 144 | + |
| 145 | + } |
| 146 | + |
| 147 | + final class ResilientCommitByRenameUnsupported extends PathIOException { |
| 148 | + public ResilientCommitByRenameUnsupported(final String path) { |
| 149 | + super(path, "ResilientCommit operations not supported"); |
| 150 | + } |
| 151 | + } |
| 152 | +} |
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