docs/compose/cli/log_printer.py

from __future__ import absolute_import
from __future__ import unicode_literals

import sys
from collections import namedtuple
from itertools import cycle
from threading import Thread

from six.moves import _thread as thread
from six.moves.queue import Empty
from six.moves.queue import Queue

from . import colors
from compose import utils
from compose.cli.signals import ShutdownException
from compose.utils import split_buffer


class LogPresenter(object):

    def __init__(self, prefix_width, color_func):
        self.prefix_width = prefix_width
        self.color_func = color_func

    def present(self, container, line):
        prefix = container.name_without_project.ljust(self.prefix_width)
        return '{prefix} {line}'.format(
            prefix=self.color_func(prefix + ' |'),
            line=line)


def build_log_presenters(service_names, monochrome):
    """Return an iterable of functions.

    Each function can be used to format the logs output of a container.
    """
    prefix_width = max_name_width(service_names)

    def no_color(text):
        return text

    for color_func in cycle([no_color] if monochrome else colors.rainbow()):
        yield LogPresenter(prefix_width, color_func)


def max_name_width(service_names, max_index_width=3):
    """Calculate the maximum width of container names so we can make the log
    prefixes line up like so:

    db_1  | Listening
    web_1 | Listening
    """
    return max(len(name) for name in service_names) + max_index_width


class LogPrinter(object):
    """Print logs from many containers to a single output stream."""

    def __init__(self,
                 containers,
                 presenters,
                 event_stream,
                 output=sys.stdout,
                 cascade_stop=False,
                 log_args=None):
        self.containers = containers
        self.presenters = presenters
        self.event_stream = event_stream
        self.output = utils.get_output_stream(output)
        self.cascade_stop = cascade_stop
        self.log_args = log_args or {}

    def run(self):
        if not self.containers:
            return

        queue = Queue()
        thread_args = queue, self.log_args
        thread_map = build_thread_map(self.containers, self.presenters, thread_args)
        start_producer_thread((
            thread_map,
            self.event_stream,
            self.presenters,
            thread_args))

        for line in consume_queue(queue, self.cascade_stop):
            remove_stopped_threads(thread_map)

            if not line:
                if not thread_map:
                    # There are no running containers left to tail, so exit
                    return
                # We got an empty line because of a timeout, but there are still
                # active containers to tail, so continue
                continue

            self.output.write(line)
            self.output.flush()


def remove_stopped_threads(thread_map):
    for container_id, tailer_thread in list(thread_map.items()):
        if not tailer_thread.is_alive():
            thread_map.pop(container_id, None)


def build_thread(container, presenter, queue, log_args):
    tailer = Thread(
        target=tail_container_logs,
        args=(container, presenter, queue, log_args))
    tailer.daemon = True
    tailer.start()
    return tailer


def build_thread_map(initial_containers, presenters, thread_args):
    return {
        container.id: build_thread(container, next(presenters), *thread_args)
        for container in initial_containers
    }


class QueueItem(namedtuple('_QueueItem', 'item is_stop exc')):

    @classmethod
    def new(cls, item):
        return cls(item, None, None)

    @classmethod
    def exception(cls, exc):
        return cls(None, None, exc)

    @classmethod
    def stop(cls):
        return cls(None, True, None)


def tail_container_logs(container, presenter, queue, log_args):
    generator = get_log_generator(container)

    try:
        for item in generator(container, log_args):
            queue.put(QueueItem.new(presenter.present(container, item)))
    except Exception as e:
        queue.put(QueueItem.exception(e))
        return

    if log_args.get('follow'):
        queue.put(QueueItem.new(presenter.color_func(wait_on_exit(container))))
    queue.put(QueueItem.stop())


def get_log_generator(container):
    if container.has_api_logs:
        return build_log_generator
    return build_no_log_generator


def build_no_log_generator(container, log_args):
    """Return a generator that prints a warning about logs and waits for
    container to exit.
    """
    yield "WARNING: no logs are available with the '{}' log driver\n".format(
        container.log_driver)


def build_log_generator(container, log_args):
    # if the container doesn't have a log_stream we need to attach to container
    # before log printer starts running
    if container.log_stream is None:
        stream = container.logs(stdout=True, stderr=True, stream=True, **log_args)
    else:
        stream = container.log_stream

    return split_buffer(stream)


def wait_on_exit(container):
    exit_code = container.wait()
    return "%s exited with code %s\n" % (container.name, exit_code)


def start_producer_thread(thread_args):
    producer = Thread(target=watch_events, args=thread_args)
    producer.daemon = True
    producer.start()


def watch_events(thread_map, event_stream, presenters, thread_args):
    for event in event_stream:
        if event['action'] == 'stop':
            thread_map.pop(event['id'], None)

        if event['action'] != 'start':
            continue

        if event['id'] in thread_map:
            if thread_map[event['id']].is_alive():
                continue
            # Container was stopped and started, we need a new thread
            thread_map.pop(event['id'], None)

        thread_map[event['id']] = build_thread(
            event['container'],
            next(presenters),
            *thread_args)


def consume_queue(queue, cascade_stop):
    """Consume the queue by reading lines off of it and yielding them."""
    while True:
        try:
            item = queue.get(timeout=0.1)
        except Empty:
            yield None
            continue
        # See https://github.com/docker/compose/issues/189
        except thread.error:
            raise ShutdownException()

        if item.exc:
            raise item.exc

        if item.is_stop:
            if cascade_stop:
                raise StopIteration
            else:
                continue

        yield item.item