BodyProducerAdapter.java

/*
 * Copyright © 2015 Cask Data, Inc.
 *
 * Licensed 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 co.cask.cdap.internal.app.runtime.service.http;

import co.cask.cdap.api.Transactional;
import co.cask.cdap.api.TxRunnable;
import co.cask.cdap.api.data.DatasetContext;
import co.cask.cdap.api.service.http.HttpContentProducer;
import co.cask.cdap.common.lang.ClassLoaders;
import co.cask.http.BodyProducer;
import org.apache.twill.common.Cancellable;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.buffer.ChannelBuffers;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.nio.ByteBuffer;

/**
 * An adapter class to delegate calls from {@link HttpContentProducer} to {@link BodyProducer}
 */
public class BodyProducerAdapter extends BodyProducer {

  private static final Logger LOG = LoggerFactory.getLogger(BodyProducerAdapter.class);

  private final HttpContentProducer delegate;
  private final Transactional transactional;
  private final ClassLoader programContextClassloader;
  private final TransactionalHttpServiceContext serviceContext;
  private final Cancellable contextReleaser;
  private boolean completed;

  public BodyProducerAdapter(HttpContentProducer delegate, Transactional transactional,
                             ClassLoader programContextClassLoader,
                             TransactionalHttpServiceContext serviceContext, Cancellable contextReleaser) {
    this.delegate = delegate;
    this.transactional = transactional;
    this.programContextClassloader = programContextClassLoader;
    this.serviceContext = serviceContext;
    this.contextReleaser = contextReleaser;
  }

  @Override
  public long getContentLength() {
    ClassLoader oldClassLoader = ClassLoaders.setContextClassLoader(programContextClassloader);
    try {
      return delegate.getContentLength();
    } finally {
      ClassLoaders.setContextClassLoader(oldClassLoader);
    }
  }

  @Override
  public ChannelBuffer nextChunk() throws Exception {
    ByteBuffer buffer;
    ClassLoader oldClassLoader = ClassLoaders.setContextClassLoader(programContextClassloader);
    try {
      buffer = delegate.nextChunk(transactional);
    } finally {
      ClassLoaders.setContextClassLoader(oldClassLoader);
    }
    return ChannelBuffers.wrappedBuffer(buffer);
  }

  @Override
  public void finished() throws Exception {
    transactional.execute(new TxRunnable() {
      @Override
      public void run(DatasetContext context) throws Exception {
        delegate.onFinish();
      }
    });

    try {
      serviceContext.dismissTransactionContext();
    } finally {
      completed = true;
      contextReleaser.cancel();
    }
  }

  @Override
  public void handleError(final Throwable throwable) {
    if (completed) {
      return;
    }

    // To the HttpContentProducer, if there is error, no other methods will be triggered
    completed = true;
    try {
      transactional.execute(new TxRunnable() {
        @Override
        public void run(DatasetContext context) throws Exception {
          delegate.onError(throwable);
        }
      });
    } catch (Throwable t) {
      throwable.addSuppressed(t);

      // nothing much can be done. Simply emit a debug log.
      LOG.debug("Exception in calling HttpContentProducer.onError.", t);
    }

    try {
      serviceContext.dismissTransactionContext();
    } finally {
      contextReleaser.cancel();
    }
  }
}