baseimage-tutorial-framework/lib/tfw/components/process_managing_event_handler.py

# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
# All Rights Reserved. See LICENSE file for details.

import logging
from xmlrpc.client import Fault as SupervisorFault

from tfw.event_handlers import FrontendEventHandlerBase
from tfw.mixins.supervisor_mixin import SupervisorMixin, SupervisorLogMixin
from tfw.components.directory_monitor import with_monitor_paused

LOG = logging.getLogger(__name__)


class ProcessManager(SupervisorMixin, SupervisorLogMixin):
    def __init__(self):
        self.commands = {
            'start':   self.start_process,
            'stop':    self.stop_process,
            'restart': self.restart_process
        }

    def __call__(self, command, process_name):
        return self.commands[command](process_name)


class ProcessManagingEventHandler(FrontendEventHandlerBase):
    """
    Event handler that can manage processes managed by supervisor.

    This EventHandler accepts messages that have a data['command'] key specifying
    a command to be executed.
    Every message must contain a data['process_name'] field with the name of the
    process to manage. This is the name specified in supervisor config files like so:
    [program:someprogram]

    Commands available: start, stop, restart, readlog
    (the names are as self-documenting as it gets)
    """
    def __init__(self, key, dirmonitor=None, log_tail=0):
        super().__init__(key)
        self.monitor = dirmonitor
        self.processmanager = ProcessManager()
        self.log_tail = log_tail

    @with_monitor_paused
    def handle_event(self, message):
        try:
            data = message['data']
            try:
                self.processmanager(data['command'], data['process_name'])
            except SupervisorFault as fault:
                message['data']['error'] = fault.faultString
            finally:
                message['data']['stdout'] = self.processmanager.read_stdout(
                    data['process_name'],
                    self.log_tail
                )
                message['data']['stderr'] = self.processmanager.read_stderr(
                    data['process_name'],
                    self.log_tail
                )
            return message
        except KeyError:
            LOG.error('IGNORING MESSAGE: Invalid message received: %s', message)