Github user zentol commented on a diff in the pull request:
https://github.com/apache/flink/pull/4397#discussion_r129580758
--- Diff:
flink-core/src/main/java/org/apache/flink/core/fs/ConsistencyLevel.java ---
@@ -0,0 +1,116 @@
+/*
+ * 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.core.fs;
+
+/**
+ * An enumeration describing the level of consistency offered by a {@link
FileSystem}.
+ *
+ * <p>The consistency levels described here make statements about the
visibility
+ * of file existence and file contents in the presence of <i>new file
creation</i>,
+ * <i>file deletion</i>, <i>file renaming</i>, and <i>directory
listing</i>.
+ *
+ * <p>An operation is defined as consistent if the following holds: After
the function
+ * call triggering the operation returns, its result is immediately
reflected in
+ * in the view presented to any other party calling a file system function.
+ *
+ * <p>Please note that these levels do not make any statements about the
effects or visibility of
+ * file content modification or file appends. In fact, content
modification or appending are
+ * not supported in various file systems.
+ *
+ * <p>Some of these consistency levels indicate that the storage system
does not actually
+ * qualify to be called a FileSystem, but rather a blob-/object store.
+ */
+public enum ConsistencyLevel {
+
+ /**
+ * This consistency level only guarantees that files are visible with a
consistent
+ * view of their contents after their initial creation, once the
writing stream has been closed.
+ * Any modifications, renames, deletes are not guaranteed to be
immediately visible in a
+ * consistent manner.
+ *
+ * <p>To access a file/object consistently, the full path/key must be
provided. Enumeration
+ * of files/objects is not consistent.
+ *
+ * <p>An example of a storage system with this consistency level is
Amazon's S3 object store.
+ *
+ * <p>This is the weakest consistency level with which Flink's
checkpointing can work.
+ *
+ * <b>Summary:</b>
+ * <ul>
+ * <li>New file creation: Consistent
+ * <li>File deletion: NOT consistent
+ * <li>File renaming: NOT consistent
+ * <li>Directory listing: NOT consistent
+ * </ul>
+ */
+ READ_AFTER_CREATE,
+
+ /**
+ * This consistency level guarantees that files are visible with a
consistent
+ * view of their contents after their initial creation, and after
renaming them.
+ * The non-existence is consistently visible after delete operations.
+ *
+ * <p>To access a file/object consistently, the full path/key must be
provided. Enumeration
+ * of files/objects is not necessarily consistent.
+ *
+ * <b>Summary:</b>
+ * <ul>
+ * <li>New file creation: consistent
+ * <li>File deletion: consistent
+ * <li>File renaming: consistent
+ * <li>Directory listing: NOT consistent
+ * </ul>
+ */
+ CONSISTENT_RENAME_DELETE,
+
+ /**
+ * This consistency level guarantees that files are visible with a
consistent
+ * view of their contents after their initial creation, as well as
after renaming operations.
+ * File deletion is immediately visible to all parties.
+ *
+ * <p>Directory listings are consistent, meaning after file
creation/rename/delete, the file
+ * existence or non-existence is reflected when enumerating the parent
directory's contents.
+ *
+ * <p>An example of storage systems and file systems falling under this
consistency level are
+ * HDFS, MapR FS, and the Windows file systems.
+ *
+ * <b>Summary:</b>
+ * <ul>
+ * <li>New file creation: consistent
+ * <li>File deletion: consistent
+ * <li>File renaming: consistent, but not necessarily atomic
--- End diff --
Is atomic renaming guaranteed for `CONSISTENT_RENAME_DELETE`? If not, how
important is this atomicity for us? Based on the names one would assume that
`LIST_RENAME_DELETE` is all-around "better" than `RENAME_DELETE`, which
currently isn't the case and could lead to subtle bugs if this is actually
relevant for us.
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