__init__.py

# coding: utf-8
#
# Copyright 2011 Yesudeep Mangalapilly <yesudeep@gmail.com>
# Copyright 2012 Google, Inc & contributors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
:module: watchdog.tricks
:synopsis: Utility event handlers.
:author: yesudeep@google.com (Yesudeep Mangalapilly)
:author: contact@tiger-222.fr (Mickaël Schoentgen)

Classes
-------
.. autoclass:: Trick
   :members:
   :show-inheritance:

.. autoclass:: LoggerTrick
   :members:
   :show-inheritance:

.. autoclass:: ShellCommandTrick
   :members:
   :show-inheritance:

.. autoclass:: AutoRestartTrick
   :members:
   :show-inheritance:

"""

import functools
import logging
import os
import signal
import subprocess
import time

from watchdog.events import PatternMatchingEventHandler
from watchdog.utils import echo
from watchdog.utils.process_watcher import ProcessWatcher

logger = logging.getLogger(__name__)
echo_events = functools.partial(echo.echo, write=lambda msg: logger.info(msg))


class Trick(PatternMatchingEventHandler):

    """Your tricks should subclass this class."""

    @classmethod
    def generate_yaml(cls):
        context = dict(module_name=cls.__module__,
                       klass_name=cls.__name__)
        template_yaml = """- %(module_name)s.%(klass_name)s:
  args:
  - argument1
  - argument2
  kwargs:
    patterns:
    - "*.py"
    - "*.js"
    ignore_patterns:
    - "version.py"
    ignore_directories: false
"""
        return template_yaml % context


class LoggerTrick(Trick):

    """A simple trick that does only logs events."""

    def on_any_event(self, event):
        pass

    @echo_events
    def on_modified(self, event):
        pass

    @echo_events
    def on_deleted(self, event):
        pass

    @echo_events
    def on_created(self, event):
        pass

    @echo_events
    def on_moved(self, event):
        pass


class ShellCommandTrick(Trick):

    """Executes shell commands in response to matched events."""

    def __init__(self, shell_command=None, patterns=None, ignore_patterns=None,
                 ignore_directories=False, wait_for_process=False,
                 drop_during_process=False):
        super().__init__(
            patterns=patterns, ignore_patterns=ignore_patterns,
            ignore_directories=ignore_directories)
        self.shell_command = shell_command
        self.wait_for_process = wait_for_process
        self.drop_during_process = drop_during_process

        self.process = None
        self._process_watchers = set()

    def on_any_event(self, event):
        from string import Template

        if self.drop_during_process and self.is_process_running():
            return

        if event.is_directory:
            object_type = 'directory'
        else:
            object_type = 'file'

        context = {
            'watch_src_path': event.src_path,
            'watch_dest_path': '',
            'watch_event_type': event.event_type,
            'watch_object': object_type,
        }

        if self.shell_command is None:
            if hasattr(event, 'dest_path'):
                context.update({'dest_path': event.dest_path})
                command = 'echo "${watch_event_type} ${watch_object} from ${watch_src_path} to ${watch_dest_path}"'
            else:
                command = 'echo "${watch_event_type} ${watch_object} ${watch_src_path}"'
        else:
            if hasattr(event, 'dest_path'):
                context.update({'watch_dest_path': event.dest_path})
            command = self.shell_command

        command = Template(command).safe_substitute(**context)
        self.process = subprocess.Popen(command, shell=True)
        if self.wait_for_process:
            self.process.wait()
        else:
            process_watcher = ProcessWatcher(self.process, None)
            self._process_watchers.add(process_watcher)
            process_watcher.process_termination_callback = \
                functools.partial(self._process_watchers.discard, process_watcher)
            process_watcher.start()

    def is_process_running(self):
        return self._process_watchers or (self.process is not None and self.process.poll())


class AutoRestartTrick(Trick):

    """Starts a long-running subprocess and restarts it on matched events.

    The command parameter is a list of command arguments, such as
    `['bin/myserver', '-c', 'etc/myconfig.ini']`.

    Call `start()` after creating the Trick. Call `stop()` when stopping
    the process.
    """

    def __init__(self, command, patterns=None, ignore_patterns=None,
                 ignore_directories=False, stop_signal=signal.SIGINT,
                 kill_after=10):
        super().__init__(
            patterns=patterns, ignore_patterns=ignore_patterns,
            ignore_directories=ignore_directories)
        self.command = command
        self.stop_signal = stop_signal
        self.kill_after = kill_after

        self.process = None
        self.process_watcher = None

    def start(self):
        # windows doesn't have setsid
        self.process = subprocess.Popen(self.command, preexec_fn=getattr(os, 'setsid', None))
        self.process_watcher = ProcessWatcher(self.process, self._restart)
        self.process_watcher.start()

    def stop(self):
        if self.process is None:
            return

        if self.process_watcher is not None:
            self.process_watcher.stop()
            self.process_watcher = None

        def kill_process(stop_signal):
            if hasattr(os, 'getpgid') and hasattr(os, 'killpg'):
                os.killpg(os.getpgid(self.process.pid), stop_signal)
            else:
                os.kill(self.process.pid, self.stop_signal)

        try:
            kill_process(self.stop_signal)
        except OSError:
            # Process is already gone
            pass
        else:
            kill_time = time.time() + self.kill_after
            while time.time() < kill_time:
                if self.process.poll() is not None:
                    break
                time.sleep(0.25)
            else:
                try:
                    kill_process(9)
                except OSError:
                    # Process is already gone
                    pass
        self.process = None

    @echo_events
    def on_any_event(self, event):
        self._restart()

    def _restart(self):
        self.stop()
        self.start()