content: /*
   * 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.beam.runners.dataflow.worker.status;
  
  import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  import java.io.File;
  import java.io.IOException;
  import javax.management.InstanceNotFoundException;
  import javax.management.MBeanException;
  import javax.management.MalformedObjectNameException;
  import javax.management.ReflectionException;
  import javax.servlet.ServletOutputStream;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  import org.apache.beam.runners.dataflow.worker.util.MemoryMonitor;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.io.Files;
  
  /**
   * Respond to /heapz with a page allowing downloading of the heap dumps.
   *
   * <p>Respond to /heapz?action=download with a download of the actual heap dump.
   *
   * <p><b>Not actually serializable</b>. Its superclass is serializable but this subclass is not.
   */
  @SuppressFBWarnings("SE_BAD_FIELD") // not serializable
  public class HeapzServlet extends BaseStatusServlet {
  
    private final MemoryMonitor memoryMonitor;
  
    public HeapzServlet(MemoryMonitor memoryMonitor) {
      super("heapz");
      this.memoryMonitor = memoryMonitor;
    }
  
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
      String action = req.getParameter("action");
      if (action == null || action.isEmpty()) {
        resp.setContentType("text/html;charset=utf-8");
        resp.setStatus(HttpServletResponse.SC_OK);
  
        ServletOutputStream writer = resp.getOutputStream();
        writer.println("<html>");
        writer.println(
            String.format(
                "Click <a href=\"%s\">here to download heap dump</a>", getPath("action=download")));
        writer.println("</html>");
        return;
      } else if ("download".equals(action)) {
        doDownload(resp);
      }
    }
  
    private void doDownload(HttpServletResponse resp) throws IOException {
      File file;
  
      try {
        file = memoryMonitor.dumpHeap();
      } catch (MalformedObjectNameException
          | InstanceNotFoundException
          | ReflectionException
          | MBeanException e) {
        resp.setContentType("text/html;charset=utf-8");
        resp.setStatus(HttpServletResponse.SC_OK);
  
        ServletOutputStream writer = resp.getOutputStream();
        writer.println("<html>\nFailed to dump heap: <br>\n<pre>");
        writer.println(e.toString());
        writer.println("</pre>\n</html>");
        return;
      }
  
      resp.setContentType("application/octet-stream");
      resp.setContentLength((int) file.length());
      resp.setHeader(
          "Content-Disposition", String.format("attachment; filename=\"%s\"", file.getName()));
  
      try {
        Files.copy(file, resp.getOutputStream());
        resp.setStatus(HttpServletResponse.SC_OK);
      } catch (IOException e) {
        resp.reset();
        resp.setContentType("text/html;charset=utf-8");
        ServletOutputStream writer = resp.getOutputStream();
        writer.println("<html>\nFailed to dump heap: <br>\n<pre>\n");
        writer.println(e.toString());
        writer.println("</pre>\n</html>");
        resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
      }
    }
  }
  