def start_spark(self):
        """Start spark processes.
        In STANDALONE mode it starts the master and slaves. In YARN mode it just
        checks that Hadoop is running, and starts it if not.
        """

        logger.info("Starting Spark")

        if self.running:
            logger.warn("Spark was already started")
            return

        if self.mode == STANDALONE_MODE:
            proc = SshProcess(self.sbin_dir + "/start-master.sh;" +
                              self.sbin_dir + "/start-slaves.sh;",
                              self.master)
            proc.run()
            if not proc.finished_ok:
                logger.warn("Error while starting Spark")
                return
        elif self.mode == YARN_MODE:
            if not self.hc.running:
                logger.warn("YARN services must be started first")
                self.hc.start_and_wait()

        self.running = True

    def _copy_xp_output(self):
        """Copy experiment's output."""

        if self.output_path:
            remote_path = self.macro_manager.test_macros["xp.output"]  # TODO: what happens if not specified?
            local_path = os.path.join(self.output_path, str(self.comb_id))
            logger.info("Copying output to " + local_path)

            tmp_dir = "/tmp"

            # Remove file in tmp dir if exists
            proc = SshProcess("rm -rf " +
                              os.path.join(tmp_dir, os.path.basename(remote_path)),
                              self.hc.master)
            proc.run()

            # Get files in master
            self.hc.execute("fs -get " + remote_path + " " + tmp_dir,
                            verbose=False)

            # Copy files from master
            action = Get([self.hc.master],
                         [os.path.join(tmp_dir, os.path.basename(remote_path))],
                         local_path)
            action.run()

    def bootstrap(self, tar_file):

        # 0. Check that required packages are present
        required_packages = "openjdk-7-jre openjdk-7-jdk"
        check_packages = TaktukRemote("dpkg -s " + required_packages,
                                      self.hosts)
        for p in check_packages.processes:
            p.nolog_exit_code = p.nolog_error = True
        check_packages.run()
        if not check_packages.ok:
            logger.info("Packages not installed, trying to install")
            install_packages = TaktukRemote(
                "export DEBIAN_MASTER=noninteractive ; " +
                "apt-get update && apt-get install -y --force-yes " +
                required_packages, self.hosts).run()
            if not install_packages.ok:
                logger.error("Unable to install the packages")

        get_java_home = SshProcess('echo $(readlink -f /usr/bin/javac | '
                                   'sed "s:/bin/javac::")', self.master)
        get_java_home.run()
        self.java_home = get_java_home.stdout.strip()

        logger.info("All required packages are present")

        # 1. Copy hadoop tar file and uncompress
        logger.info("Copy " + tar_file + " to hosts and uncompress")
        rm_dirs = TaktukRemote("rm -rf " + self.base_dir +
                               " " + self.conf_dir,
                               self.hosts)
        put_tar = TaktukPut(self.hosts, [tar_file], "/tmp")
        tar_xf = TaktukRemote(
            "tar xf /tmp/" + os.path.basename(tar_file) + " -C /tmp",
            self.hosts)
        SequentialActions([rm_dirs, put_tar, tar_xf]).run()

        # 2. Move installation to base dir
        logger.info("Create installation directories")
        mv_base_dir = TaktukRemote(
            "mv /tmp/" + os.path.basename(tar_file).replace(".tgz", "") + " " +
            self.base_dir,
            self.hosts)
        mkdirs = TaktukRemote("mkdir -p " + self.conf_dir, self.hosts)
        chmods = TaktukRemote("chmod g+w " + self.base_dir +
                              " && chmod g+w " + self.conf_dir,
                              self.hosts)
        SequentialActions([mv_base_dir, mkdirs, chmods]).run()

        # 3. Specify environment variables
        command = "cat >> " + self.conf_dir + "/spark-env.sh << EOF\n"
        command += "JAVA_HOME=" + self.java_home + "\n"
        command += "SPARK_LOG_DIR=" + self.logs_dir + "\n"
        if self.hc:
            command += "HADOOP_CONF_DIR=" + self.hc.conf_dir + "\n"
        if self.mode == YARN_MODE:
            command += "YARN_CONF_DIR=" + self.hc.conf_dir + "\n"
        command += "EOF\n"
        command += "chmod +x " + self.conf_dir + "/spark-env.sh"
        action = Remote(command, self.hosts)
        action.run()

    def execute_job(self, job, node=None, verbose=True):
        """Execute the given Spark job in the specified node.

        Args:
          job (SparkJob):
            The job object.
          node (Host, optional):
            The host were the command should be executed. If not provided,
            self.master is chosen.
          verbose (bool, optional):
            If True stdout and stderr of remote process is displayed.

        Returns (tuple of str):
          A tuple with the standard and error outputs of the process executing
          the job.
        """

        if not self.running:
            logger.warn("The cluster was stopped. Starting it automatically")
            self.start()

        if node is None:
            node = self.master

        exec_dir = "/tmp"

        # Copy necessary files to cluster
        files_to_copy = job.get_files_to_copy()
        action = Put([node], files_to_copy, exec_dir)
        action.run()

        # Get command
        command = job.get_command(exec_dir)

        # Execute
        logger.info("Executing spark job. Command = {" + self.bin_dir +
                    "/spark-submit " + command + "} in " + str(node))

        proc = SshProcess(self.bin_dir + "/spark-submit " + command, node)

        if verbose:
            red_color = '\033[01;31m'

            proc.stdout_handlers.append(sys.stdout)
            proc.stderr_handlers.append(
                ColorDecorator(sys.stderr, red_color))

        proc.start()
        proc.wait()

        # Get job info
        job.stdout = proc.stdout
        job.stderr = proc.stderr
        job.success = (proc.exit_code == 0)

        return proc.stdout, proc.stderr

    def get_version(self):
        """Return the Hadoop version.
        
        Returns (str):
          The version used by the Hadoop cluster.
        """

        proc = SshProcess("export JAVA_HOME=" + self.java_home + ";" +
                          self.bin_dir + "/hadoop version",
                          self.master)
        proc.run()
        version = proc.stdout.splitlines()[0]
        return version

    def format_dfs(self):
        """Format the distributed filesystem."""

        logger.info("Formatting HDFS")

        proc = SshProcess(self.bin_dir + "/hadoop namenode -format",
                          self.master)
        proc.run()

        if proc.finished_ok:
            logger.info("HDFS formatted successfully")
        else:
            logger.warn("Error while formatting HDFS")

    def stop_dfs(self):
        """Stop the NameNode and DataNodes."""

        self._check_initialization()

        logger.info("Stopping HDFS")

        proc = SshProcess(self.sbin_dir + "/stop-dfs.sh", self.master)
        proc.run()

        if not proc.finished_ok:
            logger.warn("Error while stopping HDFS")
        else:
            self.running_dfs = False

    def stop_map_reduce(self):
        """Stop the JobTracker and TaskTrackers."""

        self._check_initialization()

        logger.info("Stopping MapReduce")

        proc = SshProcess(self.sbin_dir + "/stop-mapred.sh", self.master)
        proc.run()

        if not proc.finished_ok:
            logger.warn("Error while stopping MapReduce")
        else:
            self.running_map_reduce = False

    def stop_yarn(self):
        """Stop the YARN ResourceManager and NodeManagers."""
        
        self._check_initialization()

        logger.info("Stopping YARN")

        proc = SshProcess(self.sbin_dir + "/stop-yarn.sh", self.master)
        proc.run()
        
        if not proc.finished_ok:
            logger.warn("Error while stopping YARN")
        else:
            self.running_yarn = False

    def stop_spark(self):
        """Stop Spark processes."""

        logger.info("Stopping Spark")

        if self.mode == STANDALONE_MODE:
            proc = SshProcess(self.sbin_dir + "/stop-slaves.sh;" +
                              self.sbin_dir + "/stop-master.sh;",
                              self.master)
            proc.run()
            if not proc.finished_ok:
                logger.warn("Error while stopping Spark")
                return

        self.running = False

    def start_dfs_and_wait(self):
        """Start the NameNode and DataNodes and wait for exiting safemode."""

        self._check_initialization()

        self.start_dfs()

        logger.info("Waiting for safe mode to be off")
        proc = SshProcess(self.bin_dir + "/hadoop dfsadmin -safemode wait",
                          self.master)
        proc.run()

        if not proc.finished_ok:
            logger.warn("Error while starting HDFS")
        else:
            self.running_dfs = True

    def execute(self, command, node=None, should_be_running=True,
                verbose=True):
        """Execute the given Hadoop command in the given node.

        Args:
          command (str):
            The command to be executed.
          node (Host, optional):
            The host were the command should be executed. If not provided,
            self.master is chosen.
          should_be_running (bool, optional):
            True if the cluster needs to be running in order to execute the
            command. If so, and it is not running, it is automatically started.
          verbose: (bool, optional):
            If True stdout and stderr of remote process is displayed.

        Returns (tuple of str):
          A tuple with the standard and error outputs of the process executing
          the command.
        """

        self._check_initialization()

        if should_be_running and not self.running:
            logger.warn("The cluster was stopped. Starting it automatically")
            self.start()

        if not node:
            node = self.master

        if verbose:
            logger.info("Executing {" + self.bin_dir + "/hadoop " +
                        command + "} in " + str(node))

        proc = SshProcess(self.bin_dir + "/hadoop " + command, node)

        if verbose:
            red_color = '\033[01;31m'

            proc.stdout_handlers.append(sys.stdout)
            proc.stderr_handlers.append(
                ColorDecorator(sys.stderr, red_color))

        proc.start()
        proc.wait()

        return (proc.stdout, proc.stderr)

    def start_yarn(self):
        """Start the YARN ResourceManager and NodeManagers."""

        logger.info("Starting YARN")
        
        self._check_initialization()
        
        proc = SshProcess(self.sbin_dir + "/start-yarn.sh", self.master)
        proc.run()        
        
        if not proc.finished_ok:
            logger.warn("Error while starting YARN")
        else:
            #TODO: get success or not from super.
            self.running_yarn = True
            if self.running_dfs:
                self.running = True

    def start_map_reduce(self):
        """Start the JobTracker and TaskTrackers."""

        self._check_initialization()

        logger.info("Starting MapReduce")

        if self.running_map_reduce:
            logger.warn("Error while starting MapReduce")
            return

        proc = SshProcess(self.sbin_dir + "/start-mapred.sh", self.master)
        proc.run()

        if not proc.finished_ok:
            logger.info("MapReduce started successfully")
        else:
            self.running_map_reduce = True

    def execute(self):
        """Execute a single test.

        Return:
          str: Local path of the file containing the process output.
        """

        test = SshProcess("java -jar " + self.jar_path +
                          " -p " + self.props_path,
                          self.host)

        # Output is stored in a local temporary file
        (_, temp_file) = tempfile.mkstemp("", "div_p2p-out-", "/tmp")
        test.stdout_handlers.append(temp_file)

        test.run()

        return temp_file

    def start_dfs(self):
        """Start the NameNode and DataNodes."""

        self._check_initialization()

        logger.info("Starting HDFS")

        if self.running_dfs:
            logger.warn("Dfs was already started")
            return

        proc = SshProcess(self.sbin_dir + "/start-dfs.sh", self.master)
        proc.run()

        if not proc.finished_ok:
            logger.warn("Error while starting HDFS")
        else:
            self.running_dfs = True

    def copy_history(self, dest, job_ids=None):
        """Copy history logs from master.
        
        Args:
          dest (str):
            The path of the local dir where the logs will be copied.
          job_ids (list of str, optional):
            A list with the ids of the jobs for which the history should be
            copied. If nothing is passed, the history of all jobs is copied.
        """

        if not os.path.exists(dest):
            logger.warning("Destination directory " + dest +
                           " does not exist. It will be created")
            os.makedirs(dest)

        history_dir = os.path.join(self.logs_dir, "history")
        if job_ids:
            pattern = " -o ".join("-name " + jid + "*" for jid in job_ids)
            list_dirs = SshProcess("find " + history_dir + " " + pattern,
                                   self.master)
            list_dirs.run()
        else:
            list_dirs = SshProcess("find " + history_dir + " -name job_*",
                                   self.master)
            list_dirs.run()

        remote_files = []
        for line in list_dirs.stdout.splitlines():
            remote_files.append(line)

        action = Get([self.master], remote_files, dest)
        action.run()

    def __force_clean(self):
        """Stop previous Hive processes (if any) and remove all remote files
        created by it."""

        hive_processes = []

        force_kill = False
        for h in self.hosts:
            proc = SshProcess("jps", self.master)
            proc.run()

            ids_to_kill = []
            for line in proc.stdout.splitlines():
                field = line.split()
                if field[1] in hive_processes:
                    ids_to_kill.append(field[0])

            if ids_to_kill:
                force_kill = True
                ids_to_kill_str = ""
                for pid in ids_to_kill:
                    ids_to_kill_str += " " + pid

                proc = SshProcess("kill -9" + ids_to_kill_str, h)
                proc.run()

        if force_kill:
            logger.info(
                "Processes from previous hadoop deployments had to be killed")

        self.clean_logs()

    def bootstrap(self, tar_file):

        # 1. Remove used dirs if existing
        action = Remote("rm -rf " + self.base_dir, self.hc.hosts)
        action.run()
        action = Remote("rm -rf " + self.conf_dir, self.hc.hosts)
        action.run()

        # 1. Copy Mahout tar file and uncompress
        logger.info("Copy " + tar_file + " to hosts and uncompress")
        action = Put(self.hc.hosts, [tar_file], "/tmp")
        action.run()
        action = Remote(
            "tar xf /tmp/" + os.path.basename(tar_file) + " -C /tmp",
            self.hc.hosts)
        action.run()

        # 2. Move installation to base dir
        logger.info("Create installation directories")
        action = Remote(
            "mv /tmp/" +
            os.path.basename(tar_file).replace(".tar.gz", "") + " " +
            self.base_dir,
            self.hc.hosts)
        action.run()

        # 3 Create other dirs
        action = Remote("mkdir -p " + self.conf_dir, self.hc.hosts)
        action.run()

        # 4. Include libraries in Hadoop's classpath
        list_dirs = SshProcess("ls -1 " + self.base_dir + "/*.jar",
                               self.hc.master)
        list_dirs.run()
        libs = " ".join(list_dirs.stdout.splitlines())
        action = Remote("cp " + libs + " " + self.hc.base_dir + "/lib",
                        self.hc.hosts)
        action.run()

        initialized = True  # No need to call initialize()

    def execute(self, command, node=None, verbose=True):

        if not node:
            node = self.hc.master

        if verbose:
            logger.info("Executing {" + self.bin_dir + "/mahout " +
                        command + "} in " + str(node))

        proc = SshProcess("export JAVA_HOME='" + self.hc.java_home + "';" +
                          "export HADOOP_HOME='" + self.hc.base_dir + "';" +
                          self.bin_dir + "/mahout " + command, node)

        if verbose:
            red_color = '\033[01;31m'

            proc.stdout_handlers.append(sys.stdout)
            proc.stderr_handlers.append(ColorDecorator(sys.stderr, red_color))

        proc.start()
        proc.wait()

        return proc.stdout, proc.stderr