/*
    * 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;
  
  import com.google.common.util.concurrent.ThreadFactoryBuilder;
  import com.google.protobuf.RpcCallback;
  import com.google.protobuf.RpcController;
  import com.google.protobuf.Service;
  import java.io.IOException;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import org.apache.commons.lang.StringUtils;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.chaos.monkies.ChaosMonkey;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.coprocessor.CoprocessorService;
  import org.apache.hadoop.hbase.coprocessor.protobuf.generated.ShellExecEndpoint;
  import org.apache.hadoop.hbase.coprocessor.protobuf.generated.ShellExecEndpoint.ShellExecRequest;
  import org.apache.hadoop.hbase.coprocessor.protobuf.generated.ShellExecEndpoint.ShellExecResponse;
  import org.apache.hadoop.util.Shell;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Receives shell commands from the client and executes them blindly. Intended only for use
   * by {@link ChaosMonkey} via {@link CoprocClusterManager}
   */
  @InterfaceAudience.Private
  public class ShellExecEndpointCoprocessor extends ShellExecEndpoint.ShellExecService implements
    Coprocessor, CoprocessorService {
    private static final Logger LOG = LoggerFactory.getLogger(ShellExecEndpointCoprocessor.class);
  
    private static final String BACKGROUND_DELAY_MS_KEY = "hbase.it.shellexeccoproc.async.delay.ms";
    private static final long DEFAULT_BACKGROUND_DELAY_MS = 1_000;
  
    private final ExecutorService backgroundExecutor;
    private Configuration conf;
  
    public ShellExecEndpointCoprocessor() {
      backgroundExecutor = Executors.newSingleThreadExecutor(
        new ThreadFactoryBuilder()
          .setNameFormat(ShellExecEndpointCoprocessor.class.getSimpleName() + "-{}")
          .setDaemon(true)
          .setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
            @Override
            public void uncaughtException(Thread t, Throwable e) {
              LOG.warn(String.format("Thread %s threw %s", t, e));
            }
          }).build());
    }
  
    @Override
    public void start(CoprocessorEnvironment env) {
      conf = env.getConfiguration();
    }
  
    @Override
    public void stop(CoprocessorEnvironment env) throws IOException {}
  
    @Override
    public void shellExec(
      final RpcController controller,
      final ShellExecRequest request,
      final RpcCallback<ShellExecResponse> done
    ) {
      final String command = request.getCommand();
      if (StringUtils.isBlank(command)) {
        throw new RuntimeException("Request contained an empty command.");
      }
      final boolean awaitResponse = !request.hasAwaitResponse() || request.getAwaitResponse();
      final String[] subShellCmd = new String[] { "/usr/bin/env", "bash", "-c", command };
      final Shell.ShellCommandExecutor shell = new Shell.ShellCommandExecutor(subShellCmd);
  
      final String msgFmt = "Executing command"
        + (!awaitResponse ? " on a background thread" : "") + ": {}";
      LOG.info(msgFmt, command);
  
      if (awaitResponse) {
        runForegroundTask(shell, controller, done);
      } else {
        runBackgroundTask(shell, done);
      }
    }
  
   private void runForegroundTask(
     final Shell.ShellCommandExecutor shell,
     final RpcController controller,
     final RpcCallback<ShellExecResponse> done
   ) {
     ShellExecResponse.Builder builder = ShellExecResponse.newBuilder();
     try {
       doExec(shell, builder);
     } catch (IOException e) {
       LOG.error("Failure launching process", e);
       controller.setFailed(e.getMessage());
     }
     done.run(builder.build());
   }
 
   private void runBackgroundTask(
     final Shell.ShellCommandExecutor shell,
     final RpcCallback<ShellExecResponse> done
   ) {
     final long sleepDuration = conf.getLong(BACKGROUND_DELAY_MS_KEY, DEFAULT_BACKGROUND_DELAY_MS);
     backgroundExecutor.submit(new Runnable() {
       @Override
       public void run() {
         try {
           // sleep first so that the RPC can ACK. race condition here as we have no means of
           // blocking until the IPC response has been acknowledged by the client.
           Thread.sleep(sleepDuration);
           ShellExecEndpointCoprocessor.this.doExec(shell, ShellExecResponse.newBuilder());
         } catch (InterruptedException e) {
           LOG.warn("Interrupted before launching process.", e);
         } catch (IOException e) {
           LOG.error("Failure launching process", e);
         }
       }
     });
     done.run(ShellExecResponse.newBuilder().build());
   }
 
   /**
    * Execute {@code shell} and collect results into {@code builder} as side-effects.
    */
   private void doExec(
     final Shell.ShellCommandExecutor shell,
     final ShellExecResponse.Builder builder
   ) throws IOException {
     try {
       shell.execute();
       builder
         .setExitCode(shell.getExitCode())
         .setStdout(shell.getOutput());
     } catch (Shell.ExitCodeException e) {
       LOG.warn("Launched process failed", e);
       builder
         .setExitCode(e.getExitCode())
         .setStdout(shell.getOutput())
         .setStderr(e.getMessage());
     }
   }
 
   @Override
   public Service getService() {
     return this;
   }
 }