| /** |
| * 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.hadoop.fs.s3a; |
| |
| import com.amazonaws.auth.InstanceProfileCredentialsProvider; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| /** |
| * A subclass of {@link InstanceProfileCredentialsProvider} that enforces |
| * instantiation of only a single instance. |
| * This credential provider calls the EC2 instance metadata service to obtain |
| * credentials. For highly multi-threaded applications, it's possible that |
| * multiple instances call the service simultaneously and overwhelm it with |
| * load. The service handles this by throttling the client with an HTTP 429 |
| * response or forcibly terminating the connection. Forcing use of a single |
| * instance reduces load on the metadata service by allowing all threads to |
| * share the credentials. The base class is thread-safe, and there is nothing |
| * that varies in the credentials across different instances of |
| * {@link S3AFileSystem} connecting to different buckets, so sharing a singleton |
| * instance is safe. |
| * |
| * As of AWS SDK 1.11.39, the SDK code internally enforces a singleton. Hadoop |
| * has upgraded its dependency to 1.11.39+ so this class is deprecated. In |
| * next major version, this will be removed. |
| * |
| * @deprecated Please use {@link InstanceProfileCredentialsProvider} instead. |
| */ |
| @InterfaceAudience.Private |
| @InterfaceStability.Stable |
| @Deprecated |
| public final class SharedInstanceProfileCredentialsProvider |
| extends InstanceProfileCredentialsProvider { |
| |
| private static final SharedInstanceProfileCredentialsProvider INSTANCE = |
| new SharedInstanceProfileCredentialsProvider(); |
| |
| /** |
| * Returns the singleton instance. |
| * |
| * @return singleton instance |
| */ |
| public static SharedInstanceProfileCredentialsProvider getInstance() { |
| return INSTANCE; |
| } |
| |
| /** |
| * Default constructor, defined explicitly as private to enforce singleton. |
| */ |
| private SharedInstanceProfileCredentialsProvider() { |
| super(); |
| } |
| } |