baseimage-tutorial-framework/tfw/components/process_management/process_log_handler.py

import logging

from .log_inotify_observer import LogInotifyObserver

LOG = logging.getLogger(__name__)


class ProcessLogHandler:
    keys = ['process.log']
    type_id = 'ControlEventHandler'

    def __init__(self, *, process_name, supervisor_uri, log_tail=0):
        self.connector, self._monitor = None, None
        self.process_name = process_name
        self._supervisor_uri = supervisor_uri
        self._initial_log_tail = log_tail

        self.command_handlers = {
            'process.log.set': self.handle_set,
            'process.log.start': self.handle_start,
            'process.log.stop': self.handle_stop
        }

    def start(self):
        if not self._monitor:
            self._monitor = LogInotifyObserver(
                connector=self.connector,
                process_name=self.process_name,
                supervisor_uri=self._supervisor_uri,
                log_tail=self._initial_log_tail
            )
            self._monitor.start()

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

    def handle_set(self, data):
        if data.get('name'):
            self._monitor.process_name = data['name']
        if data.get('tail'):
            self._monitor.log_tail = data['tail']

    def handle_start(self, _):
        self.start()

    def handle_stop(self, _):
        self._stop_monitor()

    def _stop_monitor(self):
        if self._monitor:
            self._monitor.stop()
            self._monitor = None

    def cleanup(self):
        self._stop_monitor()