baseimage-tutorial-framework/lib/tfw/builtins/log_monitoring_event_handler.py

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

import logging

from tfw.networking import Scope
from tfw.components.inotify import InotifyObserver
from tfw.mixins.supervisor_mixin import SupervisorLogMixin

from .event_handler import EventHandler

LOG = logging.getLogger(__name__)


class LogInotifyObserver(InotifyObserver, SupervisorLogMixin):
    def __init__(self, server_connector, process_name, log_tail=0):
        self._prevent_log_recursion()
        self._server_connector = server_connector
        self._process_name = process_name
        self.log_tail = log_tail
        self._procinfo = None
        InotifyObserver.__init__(self, self._get_logfiles())

    @staticmethod
    def _prevent_log_recursion():
        # This is done to prevent inotify event logs triggering themselves (infinite log recursion)
        logging.getLogger('watchdog.observers.inotify_buffer').propagate = False

    def _get_logfiles(self):
        self._procinfo = self.supervisor.getProcessInfo(self._process_name)
        return self._procinfo['stdout_logfile'], self._procinfo['stderr_logfile']

    @property
    def process_name(self):
        return self._process_name

    @process_name.setter
    def process_name(self, process_name):
        self._process_name = process_name
        self.paths = self._get_logfiles()

    def on_modified(self, event):
        self._server_connector.send_message({
            'key': 'processlog',
            'data': {
                'command': 'new_log',
                'stdout': self.read_stdout(self.process_name, tail=self.log_tail),
                'stderr': self.read_stderr(self.process_name, tail=self.log_tail)
            }
        }, Scope.BROADCAST)


class LogMonitoringEventHandler(EventHandler):
    """
    Monitors the output of a supervisor process (stdout, stderr) and
    sends the results to the frontend.

    Accepts messages that have a data['command'] key specifying
    a command to be executed.

    The API of each command is documented in their respective handler.
    """
    def __init__(self, key, process_name, log_tail=0):
        super().__init__(key, scope=Scope.WEBSOCKET)
        self.process_name = process_name
        self._monitor = LogInotifyObserver(self.server_connector, process_name, log_tail)
        self._monitor.start()

        self.command_handlers = {
            'process_name': self.handle_process_name,
            'log_tail':     self.handle_log_tail
        }

    def handle_event(self, message):
        try:
            data = message['data']
            self.command_handlers[data['command']](data)
        except KeyError:
            LOG.error('IGNORING MESSAGE: Invalid message received: %s', message)

    def handle_process_name(self, data):
        """
        Changes the monitored process.

        :param data: TFW message data containing 'value'
                     (name of the process to monitor)
        """
        self._monitor.process_name = data['value']

    def handle_log_tail(self, data):
        """
        Sets tail length of the log the monitor will send
        to the frontend (the monitor will send back the last
        'value' characters of the log).

        :param data: TFW message data containing 'value'
                     (new tail length)
        """
        self._monitor.log_tail = data['value']

    def cleanup(self):
        self._monitor.stop()