hbase-rest/src/main/java/org/apache/hadoop/hbase/rest/ProtobufStreamingOutput.java

/*
 * 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.hbase.rest;

import java.io.IOException;
import java.io.OutputStream;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.ResultScanner;
import org.apache.hadoop.hbase.rest.model.CellSetModel;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.hbase.thirdparty.javax.ws.rs.WebApplicationException;
import org.apache.hbase.thirdparty.javax.ws.rs.core.StreamingOutput;

@InterfaceAudience.Private
public class ProtobufStreamingOutput implements StreamingOutput {
  private static final Logger LOG = LoggerFactory.getLogger(ProtobufStreamingOutput.class);

  private String contentType;
  private ResultScanner resultScanner;
  private int limit;
  private int fetchSize;

  protected ProtobufStreamingOutput(ResultScanner scanner, String type, int limit, int fetchSize) {
    this.resultScanner = scanner;
    this.contentType = type;
    this.limit = limit;
    this.fetchSize = fetchSize;
    if (LOG.isTraceEnabled()) {
      LOG.trace("Created StreamingOutput with content type = " + this.contentType + " user limit : "
        + this.limit + " scan fetch size : " + this.fetchSize);
    }
  }

  @Override
  public void write(OutputStream outStream) throws IOException, WebApplicationException {
    Result[] rowsToSend;
    if (limit < fetchSize) {
      rowsToSend = this.resultScanner.next(limit);
      writeToStream(createModelFromResults(rowsToSend), this.contentType, outStream);
    } else {
      int count = limit;
      while (count > 0) {
        if (count < fetchSize) {
          rowsToSend = this.resultScanner.next(count);
        } else {
          rowsToSend = this.resultScanner.next(this.fetchSize);
        }
        if (rowsToSend.length == 0) {
          break;
        }
        count = count - rowsToSend.length;
        writeToStream(createModelFromResults(rowsToSend), this.contentType, outStream);
      }
    }
  }

  private void writeToStream(CellSetModel model, String contentType, OutputStream outStream)
    throws IOException {
    byte[] objectBytes = model.createProtobufOutput();
    outStream.write(Bytes.toBytes((short) objectBytes.length));
    outStream.write(objectBytes);
    outStream.flush();
    if (LOG.isTraceEnabled()) {
      LOG.trace("Wrote " + model.getRows().size() + " rows to stream successfully.");
    }
  }

  private CellSetModel createModelFromResults(Result[] results) {
    CellSetModel cellSetModel = new CellSetModel();
    for (int i = 0; i < results.length; i++) {
      if (results[i].isEmpty()) {
        continue;
      }
      cellSetModel.addRow(RestUtil.createRowModelFromResult(results[i]));
    }
    return cellSetModel;
  }
}