Yarn学习

public class DefaultContainerExecutor extends ContainerExecutor {
  @Override
  public int launchContainer(ContainerStartContext ctx)throws IOException, ConfigurationException {
    Container container = ctx.getContainer();   // container 在此处更多是一个资源概念，它的一些资源限制参数会在启动 进程时用到。
    Path nmPrivateContainerScriptPath = ctx.getNmPrivateContainerScriptPath();
    String user = ctx.getUser();
    Path containerWorkDir = ctx.getContainerWorkDir();
    // create container dirs on all disks
    // Create the container log-dirs on all disks
    // copy container tokens to work dir
    // copy launch script to work dir
    Path launchDst = new Path(containerWorkDir, ContainerLaunch.CONTAINER_SCRIPT);
    copyFile(nmPrivateContainerScriptPath, launchDst, user);
    // Create new local launch wrapper script
    LocalWrapperScriptBuilder sb = getLocalWrapperScriptBuilder(containerIdStr, containerWorkDir); 

    Path pidFile = getPidFilePath(containerId);
    sb.writeLocalWrapperScript(launchDst, pidFile);
    
    // create log dir under app
    // fork script
    Shell.CommandExecutor shExec = null;
    try {
      setScriptExecutable(launchDst, user);
      setScriptExecutable(sb.getWrapperScriptPath(), user);
      shExec = buildCommandExecutor(sb.getWrapperScriptPath().toString(),containerIdStr, user, pidFile, container.getResource(),new File(containerWorkDir.toUri().getPath()),container.getLaunchContext().getEnvironment());
      shExec.execute();
    } catch (IOException e) {

    } finally {
      if (shExec != null) shExec.close();
    }
    return 0;
  }
}
public static class ShellCommandExecutor extends Shell implements CommandExecutor {
  public void execute() throws IOException {
    this.run(); // ==> runCommand
  }
  private void runCommand() throws IOException {
    ProcessBuilder builder = new ProcessBuilder(getExecString());
    builder.environment().putAll(this.environment);
    builder.directory(this.dir);
    ...
    process = builder.start();
    ...
  }
}
public final class ProcessBuilder{
  public Process start() throws IOException {
    return ProcessImpl.start(cmdarray,environment, dir,redirects,redirectErrorStream);                             
  }
}