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

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

import logging
from os.path import dirname

from watchdog.events import PatternMatchingEventHandler as PatternMatchingWatchdogEventHandler

from tfw.networking.event_handlers import ServerUplinkConnector
from tfw.decorators import RateLimiter
from tfw.mixins import ObserverMixin, SupervisorLogMixin


class LogMonitor(ObserverMixin):
    def __init__(self, process_name, log_tail=0):
        self.prevent_log_recursion()
        ObserverMixin.__init__(self)
        event_handler = SendLogWatchdogEventHandler(process_name, log_tail=log_tail)
        self.observer.schedule(
            event_handler,
            event_handler.path
        )

    @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


class SendLogWatchdogEventHandler(PatternMatchingWatchdogEventHandler, SupervisorLogMixin):
    def __init__(self, process_name, log_tail=0):
        self.acquire_own_supervisor_instance()  # This thread-localises the xmlrpc client
        self.process_name = process_name
        self.procinfo = self.supervisor.getProcessInfo(self.process_name)
        super().__init__([self.procinfo['stdout_logfile'], self.procinfo['stderr_logfile']])
        self.uplink = ServerUplinkConnector()
        self.log_tail = log_tail

    @property
    def path(self):
        return dirname(self.procinfo['stdout_logfile'])

    @RateLimiter(rate_per_second=5)
    def on_modified(self, event):
        self.uplink.send({
            '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)
            }
        })