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Huawei OBS Under File System implementation
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/*
 * 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.obs;

import alluxio.retry.RetryPolicy;
import alluxio.underfs.MultiRangeObjectInputStream;

import com.obs.services.ObsClient;
import com.obs.services.exception.ObsException;
import com.obs.services.model.GetObjectRequest;
import com.obs.services.model.ObjectMetadata;
import com.obs.services.model.ObsObject;
import org.apache.http.HttpStatus;
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 OBS. This input stream returns 0 when calling read with an empty
 * buffer.
 */
@NotThreadSafe
public class OBSInputStream extends MultiRangeObjectInputStream {
  private static final Logger LOG = LoggerFactory.getLogger(OBSInputStream.class);

  /**
   * Bucket name of the OBS bucket.
   */
  private final String mBucketName;

  /**
   * Key of the file in OBS.
   */
  private final String mKey;

  /**
   * The OBS client.
   */
  private final ObsClient mObsClient;

  /**
   * 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 OBSInputStream}.
   *
   * @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
   */
  OBSInputStream(String bucketName, String key, ObsClient client, RetryPolicy retryPolicy,
      long multiRangeChunkSize) throws IOException {
    this(bucketName, key, client, 0L, retryPolicy, multiRangeChunkSize);
  }

  /**
   * Creates a new instance of {@link OBSInputStream}.
   *
   * @param bucketName the name of the bucket
   * @param key the key of the file
   * @param client the OBS client
   * @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
   */
  OBSInputStream(String bucketName, String key, ObsClient client, long position,
      RetryPolicy retryPolicy, long multiRangeChunkSize) throws IOException {
    super(multiRangeChunkSize);
    mBucketName = bucketName;
    mKey = key;
    mObsClient = client;
    mPos = position;
    ObjectMetadata meta = mObsClient.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);
    req.setRangeStart(startPos);
    req.setRangeEnd(endPos < mContentLength ? endPos - 1 : mContentLength - 1);
    ObsException lastException = null;
    while (mRetryPolicy.attempt()) {
      try {
        ObsObject obj = mObsClient.getObject(req);
        return new BufferedInputStream(obj.getObjectContent());
      } catch (ObsException e) {
        System.out.println(e.getResponseCode());
        LOG.warn("Attempt {} to open key {} in bucket {} failed with exception : {}",
            mRetryPolicy.getAttemptCount(), mKey, mBucketName, e.toString());
        if (e.getResponseCode() != HttpStatus.SC_NOT_FOUND) {
          throw new IOException(e);
        }
        // Key does not exist
        lastException = e;
      }
    }
    // Failed after retrying key does not exist
    throw new IOException(lastException);
  }
}