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"""Module for handling messages and concurrency for run-webkit-tests.

Testing is accomplished by having a manager (TestRunner) gather all of the
tests to be run, and sending messages to a pool of workers (TestShellThreads)
to run each test. Each worker communicates with one driver (usually
DumpRenderTree) to run one test at a time and then compare the output against
what we expected to get.

This modules provides a message broker that connects the manager to the
workers: it provides a messaging abstraction and message loops, and
handles launching threads and/or processes depending on the
requested configuration.
"""

import logging
import sys
import time
import traceback

import dump_render_tree_thread

_log = logging.getLogger(__name__)


def get(port, options):
    """Return an instance of a WorkerMessageBroker."""
    worker_model = options.worker_model
    if worker_model == 'inline':
        return _InlineBroker(port, options)
    if worker_model == 'threads':
        return _MultiThreadedBroker(port, options)
    raise ValueError('unsupported value for --worker-model: %s' % worker_model)


class _WorkerMessageBroker(object):
    def __init__(self, port, options):
        self._port = port
        self._options = options
        self._num_workers = int(self._options.child_processes)

        # This maps worker names to their TestShellThread objects.
        self._threads = {}

    def start_workers(self, test_runner):
        """Starts up the pool of workers for running the tests.

        Args:
            test_runner: a handle to the manager/TestRunner object
        """
        self._test_runner = test_runner
        for worker_number in xrange(self._num_workers):
            thread = self.start_worker(worker_number)
            self._threads[thread.name()] = thread
        return self._threads.values()

    def start_worker(self, worker_number):
        # FIXME: Replace with something that isn't a thread.
        # Note: Don't start() the thread! If we did, it would actually
        # create another thread and start executing it, and we'd no longer
        # be single-threaded.
        return dump_render_tree_thread.TestShellThread(self._port,
            self._options, worker_number,
            self._test_runner._current_filename_queue,
            self._test_runner._result_queue)

    def run_message_loop(self):
        """Loop processing messages until done."""
        raise NotImplementedError

    def cancel_workers(self):
        """Cancel/interrupt any workers that are still alive."""
        pass

    def cleanup(self):
        """Perform any necessary cleanup on shutdown."""
        pass


class _InlineBroker(_WorkerMessageBroker):
    def run_message_loop(self):
        thread = self._threads.values()[0]
        thread.run_in_main_thread(self._test_runner,
                                  self._test_runner._current_result_summary)
        self._test_runner.update()


class _MultiThreadedBroker(_WorkerMessageBroker):
    def start_worker(self, worker_number):
        thread = _WorkerMessageBroker.start_worker(self, worker_number)
        thread.start()
        return thread

    def run_message_loop(self):
        # Loop through all the threads waiting for them to finish.
        some_thread_is_alive = True
        while some_thread_is_alive:
            some_thread_is_alive = False
            t = time.time()
            for thread in self._threads.values():
                exception_info = thread.exception_info()
                if exception_info is not None:
                    # Re-raise the thread's exception here to make it
                    # clear that testing was aborted. Otherwise,
                    # the tests that did not run would be assumed
                    # to have passed.
                    raise exception_info[0], exception_info[1], exception_info[2]

                if thread.isAlive():
                    some_thread_is_alive = True
                    next_timeout = thread.next_timeout()
                    if next_timeout and t > next_timeout:
                        log_wedged_worker(thread.name(), thread.id())
                        thread.clear_next_timeout()

            self._test_runner.update()

            if some_thread_is_alive:
                time.sleep(0.01)

    def cancel_workers(self):
        for thread in self._threads.values():
            thread.cancel()


def log_wedged_worker(name, id):
    """Log information about the given worker state."""
    stack = _find_thread_stack(id)
    assert(stack is not None)
    _log.error("")
    _log.error("%s (tid %d) is wedged" % (name, id))
    _log_stack(stack)
    _log.error("")


def _find_thread_stack(id):
    """Returns a stack object that can be used to dump a stack trace for
    the given thread id (or None if the id is not found)."""
    for thread_id, stack in sys._current_frames().items():
        if thread_id == id:
            return stack
    return None


def _log_stack(stack):
    """Log a stack trace to log.error()."""
    for filename, lineno, name, line in traceback.extract_stack(stack):
        _log.error('File: "%s", line %d, in %s' % (filename, lineno, name))
        if line:
            _log.error('  %s' % line.strip())