content: /*
   * 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.spark.network.sasl;
  
  import java.nio.ByteBuffer;
  import java.util.concurrent.ConcurrentHashMap;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.spark.network.util.JavaUtils;
  
  /**
   * A class that manages shuffle secret used by the external shuffle service.
   */
  public class ShuffleSecretManager implements SecretKeyHolder {
    private static final Logger logger = LoggerFactory.getLogger(ShuffleSecretManager.class);
  
    private final ConcurrentHashMap<String, String> shuffleSecretMap;
  
    // Spark user used for authenticating SASL connections
    // Note that this must match the value in org.apache.spark.SecurityManager
    private static final String SPARK_SASL_USER = "sparkSaslUser";
  
    public ShuffleSecretManager() {
      shuffleSecretMap = new ConcurrentHashMap<>();
    }
  
    /**
     * Register an application with its secret.
     * Executors need to first authenticate themselves with the same secret before
     * fetching shuffle files written by other executors in this application.
     */
    public void registerApp(String appId, String shuffleSecret) {
      if (!shuffleSecretMap.contains(appId)) {
        shuffleSecretMap.put(appId, shuffleSecret);
        logger.info("Registered shuffle secret for application {}", appId);
      } else {
        logger.debug("Application {} already registered", appId);
      }
    }
  
    /**
     * Register an application with its secret specified as a byte buffer.
     */
    public void registerApp(String appId, ByteBuffer shuffleSecret) {
      registerApp(appId, JavaUtils.bytesToString(shuffleSecret));
    }
  
    /**
     * Unregister an application along with its secret.
     * This is called when the application terminates.
     */
    public void unregisterApp(String appId) {
      if (shuffleSecretMap.contains(appId)) {
        shuffleSecretMap.remove(appId);
        logger.info("Unregistered shuffle secret for application {}", appId);
      } else {
        logger.warn("Attempted to unregister application {} when it is not registered", appId);
      }
    }
  
    /**
     * Return the Spark user for authenticating SASL connections.
     */
    @Override
    public String getSaslUser(String appId) {
      return SPARK_SASL_USER;
    }
  
    /**
     * Return the secret key registered with the given application.
     * This key is used to authenticate the executors before they can fetch shuffle files
     * written by this application from the external shuffle service. If the specified
     * application is not registered, return null.
     */
    @Override
    public String getSecretKey(String appId) {
      return shuffleSecretMap.get(appId);
    }
  }
  