ServerStreamCompressionFilter.java

/*
   Copyright (c) 2015 LinkedIn Corp.

   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 com.linkedin.r2.filter.compression;

import com.linkedin.common.callback.Callback;
import com.linkedin.r2.filter.compression.streaming.AcceptEncoding;
import com.linkedin.r2.filter.compression.streaming.StreamEncodingType;
import com.linkedin.r2.message.stream.entitystream.CompositeWriter;
import com.linkedin.r2.filter.compression.streaming.PartialReader;
import com.linkedin.r2.filter.compression.streaming.StreamingCompressor;
import com.linkedin.r2.filter.message.stream.StreamFilter;
import com.linkedin.r2.message.stream.StreamException;
import com.linkedin.r2.message.stream.StreamRequest;
import com.linkedin.r2.message.stream.StreamResponse;
import com.linkedin.r2.message.stream.StreamResponseBuilder;
import com.linkedin.r2.message.stream.entitystream.EntityStream;
import com.linkedin.r2.message.stream.entitystream.EntityStreams;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import java.util.TreeMap;
import java.util.concurrent.Executor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.linkedin.r2.filter.NextFilter;
import com.linkedin.r2.message.RequestContext;
import com.linkedin.r2.transport.http.common.HttpConstants;

/**
 * Filter class for server to negotiate acceptable compression formats from clients
 * and compresses the response with the relevant headers accordingly.
 *
 * @author Ang Xu
 */
public class ServerStreamCompressionFilter implements StreamFilter
{
  private static final Logger LOG = LoggerFactory.getLogger(ServerStreamCompressionFilter.class);

  private final Set<StreamEncodingType> _supportedEncoding;
  private final Executor _executor;
  private final ServerCompressionHelper _serverCompressionHelper;


  /** Takes a comma delimited string containing standard
   * HTTP encoding headers and instantiates server compression
   * support for the said encoding types.
   * @param acceptedFilters
   */
  public ServerStreamCompressionFilter(String acceptedFilters, Executor executor)
  {
    this(acceptedFilters, executor, Integer.MAX_VALUE);
  }

  public ServerStreamCompressionFilter(String acceptedFilters, Executor executor, int compressThreshold)
  {
    this(AcceptEncoding.parseAcceptEncoding(acceptedFilters), executor, compressThreshold);
  }

  /** Instantiates a compression filter
   * that supports the compression methods in the given set in argument.
   * @param supportedEncoding
   */
  public ServerStreamCompressionFilter(StreamEncodingType[] supportedEncoding, Executor executor, int compressThreshold)
  {
    _supportedEncoding = new HashSet<StreamEncodingType>(Arrays.asList(supportedEncoding));
    _supportedEncoding.add(StreamEncodingType.IDENTITY);
    _supportedEncoding.add(StreamEncodingType.ANY);
    _executor = executor;
    _serverCompressionHelper = new ServerCompressionHelper(compressThreshold);
  }

  /**
   * Handles compression tasks for incoming requests
   */
  @Override
  public void onStreamRequest(StreamRequest req, RequestContext requestContext, Map<String, String> wireAttrs,
                              NextFilter<StreamRequest, StreamResponse> nextFilter)
  {
    try
    {
      //Check if the request is compressed, if so, decompress
      String requestContentEncoding = req.getHeader(HttpConstants.CONTENT_ENCODING);
      if (requestContentEncoding != null)
      {
        //This must be a specific compression type other than *
        StreamEncodingType encoding = StreamEncodingType.get(requestContentEncoding.trim().toLowerCase());
        if (encoding == null || encoding == StreamEncodingType.ANY)
        {
          throw new CompressionException(CompressionConstants.UNSUPPORTED_ENCODING + requestContentEncoding);
        }
        //Process the correct content-encoding types only
        StreamingCompressor compressor = encoding.getCompressor(_executor);
        if (compressor == null)
        {
          throw new CompressionException(CompressionConstants.UNKNOWN_ENCODING + encoding);
        }
        EntityStream uncompressedStream = compressor.inflate(req.getEntityStream());
        Map<String, String> headers = stripHeaders(req.getHeaders(), HttpConstants.CONTENT_ENCODING, HttpConstants.CONTENT_LENGTH);
        req = req.builder().setHeaders(headers).build(uncompressedStream);
      }

      //Get client support for compression and flag compress if need be
      String responseCompression = req.getHeader(HttpConstants.ACCEPT_ENCODING);
      if (responseCompression == null)
      {
        // per RFC 2616, section 14.3, if no Accept-Encoding field is present in a request,
        // server SHOULD use "identity" content-encoding if it is available.
        responseCompression = StreamEncodingType.IDENTITY.getHttpName();
      }
      if (!responseCompression.equalsIgnoreCase(StreamEncodingType.IDENTITY.getHttpName()))
      {
        requestContext.putLocalAttr(HttpConstants.HEADER_RESPONSE_COMPRESSION_THRESHOLD,
            _serverCompressionHelper.getResponseCompressionThreshold(req));
      }

      requestContext.putLocalAttr(HttpConstants.ACCEPT_ENCODING, responseCompression);
      nextFilter.onRequest(req, requestContext, wireAttrs);
    }
    catch (CompressionException ex)
    {
      LOG.error(ex.getMessage(), ex.getCause());
      StreamResponse streamResponse = new StreamResponseBuilder().setStatus(HttpConstants.UNSUPPORTED_MEDIA_TYPE).build(EntityStreams.emptyStream());
      nextFilter.onError(new StreamException(streamResponse, ex), requestContext, wireAttrs);
    }
  }

  /**
   * Optionally compresses outgoing response
   * */
  @Override
  public void onStreamResponse(final StreamResponse res, final RequestContext requestContext, final Map<String, String> wireAttrs,
                               final NextFilter<StreamRequest, StreamResponse> nextFilter)
  {
    StreamResponse response = res;
    try
    {
      String responseCompression = (String) requestContext.getLocalAttr(HttpConstants.ACCEPT_ENCODING);
      if (responseCompression == null)
      {
        throw new CompressionException(HttpConstants.ACCEPT_ENCODING + " not in local attribute.");
      }

      List<AcceptEncoding> parsedEncodings = AcceptEncoding.parseAcceptEncodingHeader(responseCompression, _supportedEncoding);
      StreamEncodingType selectedEncoding = AcceptEncoding.chooseBest(parsedEncodings);

      //Check if there exists an acceptable encoding
      if (selectedEncoding == null)
      {
        //Not acceptable encoding status
        response = new StreamResponseBuilder().setStatus(HttpConstants.NOT_ACCEPTABLE).build(EntityStreams.emptyStream());
      }
      else if (selectedEncoding != StreamEncodingType.IDENTITY)
      {
        final int threshold = (Integer) requestContext.getLocalAttr(HttpConstants.HEADER_RESPONSE_COMPRESSION_THRESHOLD);
        final StreamingCompressor compressor = selectedEncoding.getCompressor(_executor);
        PartialReader reader = new PartialReader(threshold, new Callback<EntityStream[]>()
        {
          @Override
          public void onError(Throwable ex)
          {
            nextFilter.onError(ex, requestContext, wireAttrs);
          }

          @Override
          public void onSuccess(EntityStream[] results)
          {
            if (results.length == 1) // entity stream is less than threshold
            {
              StreamResponse response = res.builder().build(results[0]);
              nextFilter.onResponse(response, requestContext, wireAttrs);
            }
            else
            {
              EntityStream compressedStream = compressor.deflate(EntityStreams.newEntityStream(new CompositeWriter(results)));
              StreamResponseBuilder builder = res.builder();
              // remove original content-length header if presents.
              if (builder.getHeader(HttpConstants.CONTENT_LENGTH) != null)
              {
                Map<String, String> headers = stripHeaders(builder.getHeaders(), HttpConstants.CONTENT_LENGTH);
                builder.setHeaders(headers);
              }
              StreamResponse response = builder.addHeaderValue(HttpConstants.CONTENT_ENCODING, compressor.getContentEncodingName())
                  .build(compressedStream);
              nextFilter.onResponse(response, requestContext, wireAttrs);
            }
          }
        });
        res.getEntityStream().setReader(reader);
        return;
      }
    }
    catch (CompressionException e)
    {
      LOG.error(e.getMessage(), e.getCause());
    }

    nextFilter.onResponse(response, requestContext, wireAttrs);
  }


  @Override
  public void onStreamError(Throwable ex, RequestContext requestContext, Map<String, String> wireAttrs,
                            NextFilter<StreamRequest, StreamResponse> nextFilter)
  {
    nextFilter.onError(ex, requestContext, wireAttrs);
  }

  private Map<String, String> stripHeaders(Map<String, String> headerMap, String...headers)
  {
    Map<String, String> newMap = new TreeMap<String, String>(String.CASE_INSENSITIVE_ORDER);
    newMap.putAll(headerMap);
    for (String header : headers)
    {
      newMap.remove(header);
    }
    return newMap;
  }
}