content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.underfs.oss;
  
  import alluxio.retry.RetryPolicy;
  import alluxio.underfs.MultiRangeObjectInputStream;
  
  import com.aliyun.oss.OSS;
  import com.aliyun.oss.OSSException;
  import com.aliyun.oss.model.GetObjectRequest;
  import com.aliyun.oss.model.OSSObject;
  import com.aliyun.oss.model.ObjectMetadata;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.BufferedInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import javax.annotation.concurrent.NotThreadSafe;
  
  /**
   * A stream for reading a file from OSS. This input stream returns 0 when calling read with an empty
   * buffer.
   */
  @NotThreadSafe
  public class OSSInputStream extends MultiRangeObjectInputStream {
    private static final Logger LOG = LoggerFactory.getLogger(OSSInputStream.class);
  
    /** Bucket name of the Alluxio OSS bucket. */
    private final String mBucketName;
  
    /** Key of the file in OSS to read. */
    private final String mKey;
  
    /** The OSS client for OSS operations. */
    private final OSS mOssClient;
  
    /** The size of the object in bytes. */
    private final long mContentLength;
  
    /**
     * Policy determining the retry behavior in case the key does not exist. The key may not exist
     * because of eventual consistency.
     */
    private final RetryPolicy mRetryPolicy;
  
    /**
     * Creates a new instance of {@link OSSInputStream}.
     *
     * @param bucketName the name of the bucket
     * @param key the key of the file
     * @param client the client for OSS
     * @param retryPolicy retry policy in case the key does not exist
     * @param multiRangeChunkSize the chunk size to use on this stream
     */
    OSSInputStream(String bucketName, String key, OSS client, RetryPolicy retryPolicy,
        long multiRangeChunkSize) throws IOException {
      this(bucketName, key, client, 0L, retryPolicy, multiRangeChunkSize);
    }
  
    /**
     * Creates a new instance of {@link OSSInputStream}.
     *
     * @param bucketName the name of the bucket
     * @param key the key of the file
     * @param client the client for OSS
     * @param position the position to begin reading from
     * @param retryPolicy retry policy in case the key does not exist
     * @param multiRangeChunkSize the chunk size to use on this stream
     */
    OSSInputStream(String bucketName, String key, OSS client, long position,
        RetryPolicy retryPolicy, long multiRangeChunkSize) throws IOException {
      super(multiRangeChunkSize);
      mBucketName = bucketName;
      mKey = key;
      mOssClient = client;
      mPos = position;
      ObjectMetadata meta = mOssClient.getObjectMetadata(mBucketName, key);
      mContentLength = meta == null ? 0 : meta.getContentLength();
      mRetryPolicy = retryPolicy;
    }
  
    @Override
    protected InputStream createStream(long startPos, long endPos)
        throws IOException {
      GetObjectRequest req = new GetObjectRequest(mBucketName, mKey);
      // OSS returns entire object if we read past the end
      req.setRange(startPos, endPos < mContentLength ? endPos - 1 : mContentLength - 1);
      OSSException lastException = null;
      String errorMessage = String.format("Failed to open key: %s bucket: %s", mKey, mBucketName);
      RetryPolicy retryPolicy = mRetryPolicy.copy();
      while (retryPolicy.attempt()) {
        try {
          OSSObject ossObject = mOssClient.getObject(req);
          return new BufferedInputStream(ossObject.getObjectContent());
        } catch (OSSException e) {
          errorMessage = String
              .format("Failed to open key: %s bucket: %s attempts: %d error: %s", mKey, mBucketName,
                  retryPolicy.getAttemptCount(), e.getMessage());
          if (!e.getErrorCode().equals("NoSuchKey")) {
            throw new IOException(errorMessage, e);
          }
          // Key does not exist
          lastException = e;
        }
      }
      // Failed after retrying key does not exist
      throw new IOException(errorMessage, lastException);
    }
  }
  