flink-core/src/main/java/org/apache/flink/core/fs/EntropyInjectingFileSystem.java

/*
 * 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
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 */

package org.apache.flink.core.fs;

import org.apache.flink.annotation.PublicEvolving;

/**
 * An interface to be implemented by a {@link FileSystem} that is aware of entropy injection.
 *
 * <p>Entropy injection is a technique to spread files/objects across more parallel shards of
 * a distributed storage (typically object store) by adding random characters to the beginning
 * of the path/key and hence spearing the keys across a wider domain of prefixes.
 *
 * <p>Entropy injection typically works by having a recognized marker string in paths
 * and replacing that marker with random characters.
 *
 * <p>This interface is used in conjunction with the {@link EntropyInjector} (as a poor man's
 * way to build a mix-in in Java).
 */
@PublicEvolving
public interface EntropyInjectingFileSystem {

	/**
	 * Gets the marker string that represents the substring of a path to be replaced
	 * by the entropy characters.
	 */
	String getEntropyInjectionKey();

	/**
	 * Creates a string with random entropy to be injected into a path.
	 */
	String generateEntropy();
}