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# coding=utf-8
#
# Copyright © Cloud Linux GmbH & Cloud Linux Software, Inc 2010-2019 All Rights Reserved
#
# Licensed under CLOUD LINUX LICENSE AGREEMENT
# http://cloudlinux.com/docs/LICENSE.TXT

import cProfile
import logging
import multiprocessing
import os
import pstats
import signal
import sys
import threading
import time
import traceback

from sqlalchemy.exc import (
    NoReferenceError,
    NoSuchColumnError,
    NoSuchTableError,
    SQLAlchemyError,
)

from lvestats.core.plugin import LveStatsPluginTerminated
from lvestats.core.plugin_context import PluginContext
from lvestats.lib.config import ConfigError

__author__ = 'shaman'


class PluginExecutionException(Exception):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)


class DbRecoveredException(Exception):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)


class DbRecoverFailedException(Exception):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)


class PluginTimeoutException(Exception):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)


class PluginExecutor(object):
    initial_lve_data = {'stats': {}}

    def __init__(self, config):
        self.config = config
        self.log = logging.getLogger('main_loop.plugin_executor')

        from lvestats.lib.commons.func import (  # pylint: disable=import-outside-toplevel
            get_lve_version,
        )
        PluginExecutor.initial_lve_data = {'stats': {}, 'LVE_VERSION': get_lve_version()}

    def execute(self, plugin_class, now, timeout):
        """
        Executes given plugin with provided lve_data.
        Does not modify lve_data.
        Returns updated lve_data or throws PluginExecutionException or PluginTimeoutException
        :param plugin_class: object:
        :return:
        """
        raise NotImplementedError()

    def terminate(self):
        raise NotImplementedError()


KILL_PROCESS_TIMEOUT = 20


class SameProcessPluginExecutor(PluginExecutor):
    def __init__(self, config):
        super().__init__(config)
        self.plugin_context = PluginContext(config)
        self.last_execution_time = {}
        self.lve_data = PluginExecutor.initial_lve_data.copy()

    def execute(self, plugin_class, now, timeout):
        log = logging.getLogger('main_loop.plugin_executor.same_process')
        plugin_instance = self.plugin_context.get_instance(plugin_class)
        plugin_instance.now = now

        time_passed = None

        period = getattr(plugin_instance, 'period', getattr(plugin_class, 'period', None))

        if period:
            time_passed = now - self.last_execution_time.get(plugin_class, 0)

        if period is None or period <= time_passed:
            try:
                plugin_instance.execute(self.lve_data)
                self.last_execution_time[plugin_class] = now
                return
            except (NoSuchColumnError, NoSuchTableError, NoReferenceError) as ex:
                log.exception('Database error during executing plugin that leads to need of db recreation db')

                try:
                    self.plugin_context.recover_db()
                except BaseException as exception_during_recover:
                    raise DbRecoverFailedException(exception_during_recover) from exception_during_recover

                raise DbRecoveredException() from ex
            except SQLAlchemyError as ex:
                log.exception('Database error during executing plugin that may indicate the need to recreate db. '
                              'Please check it manually.')
                raise PluginExecutionException(ex) from ex
            except BaseException as ex:
                raise PluginExecutionException(ex) from ex

    def terminate(self):
        pass


class ProcessContext(object):
    def __init__(self):
        self.mgr = multiprocessing.Manager()
        self.ns = self.mgr.Namespace()
        self.ns.last_execution_time = {}
        self.plugin_ready_event = self.mgr.Event()
        self.plugin_execution_finished_event = self.mgr.Event()
        self.plugin_execution_success_event = self.mgr.Event()
        self.db_error_event = self.mgr.Event()

        self.have_to_exit = self.mgr.Event()
        self.exited = self.mgr.Event()

    def terminate(self):
        self.mgr.shutdown()


class SeparateProcessPluginExecutor(PluginExecutor):
    def __init__(self, config, profiling_log=None):
        super().__init__(config)
        self.profiling_log = profiling_log
        self.process_context = None
        self.process = None

    @staticmethod
    def _in_separate_process(config, process_context, profiler=None, profiling_log=None):
        os.setpgrp()
        signal.signal(signal.SIGTERM, SeparateProcessPluginExecutor._child_process_sigterm_handler)
        signal.signal(signal.SIGUSR1, SeparateProcessPluginExecutor._sigusr1_handler)
        log = logging.getLogger('main_loop.plugin_executor.process')
        try:
            plugin_context = PluginContext(config)
            lve_data = PluginExecutor.initial_lve_data.copy()

            while True:
                while not process_context.plugin_ready_event.wait(timeout=1):
                    if process_context.have_to_exit.is_set():
                        process_context.plugin_execution_finished_event.set()

                        if profiler:
                            with open(profiling_log, 'a+', encoding='utf-8') as f:
                                f.write('Plugin process profile, internal time:\n')
                                stats = pstats.Stats(profiler, stream=f)
                                stats.sort_stats('time').print_stats(20)

                                f.write('Plugin process profile, cumulative time:\n')
                                stats.sort_stats('cumulative').print_stats(20)
                        process_context.exited.set()
                        return

                process_context.plugin_ready_event.clear()

                plugin_class = process_context.ns.plugin_class
                now = process_context.ns.now

                try:
                    plugin_instance = plugin_context.get_instance(plugin_class)
                except ConfigError as ce:
                    log.exception(str(ce))
                    continue
                except Exception as ex:
                    log.exception("Error during instantiating plugin")
                    process_context.ns.exception = ex
                    process_context.plugin_execution_finished_event.set()
                    continue

                plugin_instance.now = now

                period = getattr(plugin_instance, 'period', getattr(plugin_class, 'period', None))
                if period is not None:
                    period = float(period)

                time_passed = None

                last_execution_time = process_context.ns.last_execution_time

                if period is not None:
                    time_passed = now - last_execution_time.get(plugin_class, 0)

                if period is None or period <= time_passed:
                    try:
                        signal.signal(signal.SIGUSR2, SeparateProcessPluginExecutor._stop_plugin)
                        log.debug("Executing plugin %s", plugin_class)

                        t0 = time.time()
                        plugin_instance.execute(lve_data)
                        log.debug("Executing plugin %s took %f sec", plugin_class, time.time() - t0)

                        last_execution_time[plugin_class] = now
                        process_context.ns.last_execution_time = last_execution_time

                        process_context.plugin_execution_success_event.set()
                        process_context.plugin_execution_finished_event.set()
                        signal.signal(signal.SIGUSR2, signal.SIG_IGN)
                    except (NoSuchColumnError, NoSuchTableError, NoReferenceError) as ex:
                        log.exception('Database error during executing plugin that leads to need of db recreation db')
                        process_context.ns.exception = ex
                        process_context.db_error_event.set()
                        process_context.plugin_execution_finished_event.set()
                        continue
                    except SQLAlchemyError as ex:
                        log.exception('Database error during executing %s plugin that may indicate the need to '
                                      'recreate db. '
                                      'Please check it manually.', plugin_class)
                        process_context.ns.exception = ex
                        process_context.plugin_execution_finished_event.set()
                        continue
                    except LveStatsPluginTerminated:
                        log.info("Plugin %s was terminated.", plugin_class)
                        sys.exit(0)
                    except IOError as ioe:
                        log.exception("IO Error: %s", str(ioe))
                        continue
                    except Exception as ex:
                        log.exception("Other exception during execution of plugin %s", plugin_class)
                        process_context.ns.exception = ex
                        process_context.plugin_execution_finished_event.set()
                        continue
                else:
                    log.debug("plugin %s will be launched in %f sec", plugin_class, period - time_passed)
                    process_context.plugin_execution_success_event.set()
                    process_context.plugin_execution_finished_event.set()
        except Exception as ex:
            try:
                process_context.ns.exception = ex
            except IOError as e:
                # Hide "IOError: [Errno 32] Broken pipe" on KeyboardInterrupt
                # Probably there is a better way to do this
                if e.errno == 32 and isinstance(ex, EOFError):
                    return
                raise e     # don't hide any other error
            log.exception("Exception during execution in separate process")
            process_context.plugin_execution_finished_event.set()

    @staticmethod
    def _do_profile_in_separate_process(config, process_context, profiling_log):
        profiler = cProfile.Profile()
        profiler.runcall(SeparateProcessPluginExecutor._in_separate_process,
                         config,
                         process_context,
                         profiler,
                         profiling_log)

    def _make_sub_process(self, ):
        self.process_context = ProcessContext()
        target = SeparateProcessPluginExecutor._do_profile_in_separate_process if self.profiling_log else \
            SeparateProcessPluginExecutor._in_separate_process

        self.process = multiprocessing.Process(target=target,
                                               name='plugin_process',
                                               args=(self.config, self.process_context, self.profiling_log))
        self.process.start()

    @staticmethod
    def _stop_plugin(signum, frame):
        log = logging.getLogger('plugin_sigusr2_handler')
        log.info('Shutting down plugin')
        raise LveStatsPluginTerminated()

    @staticmethod
    def _child_process_sigterm_handler(signum, frame):
        log = logging.getLogger('subprocess_sigterm_handler')
        log.info('Shutting down child process')
        sys.exit(0)

    def _kill_subprocess(self, pid):
        if not pid:
            return

        os.kill(pid, signal.SIGKILL)
        self.log.debug("subprocess killed")

    def _terminate_sub_process(self):
        if not self.process or not self.process_context:
            return

        self.log.debug('Terminating subprocess')
        self.process_context.have_to_exit.set()

        if self.process_context.exited.wait(KILL_PROCESS_TIMEOUT):
            self.process = None
            self.process_context.terminate()
            self.process_context = None
            return

        self.log.debug('Killing subprocess')
        pid = self.process.pid

        try:
            self.process.terminate()
            self.process.join(KILL_PROCESS_TIMEOUT)
            if self.process.is_alive():
                self._kill_subprocess(pid)
        except Exception as ex:
            self.log.exception("Wasn't able to kill subprocess because of the error: %s", str(ex))
            self._kill_subprocess(pid)
        finally:
            self.process = None
            self.process_context.terminate()
            self.process_context = None

    @staticmethod
    def _sigusr1_handler(signum, frame):
        log = logging.getLogger('stack tracer')
        log.info("--- Threads stack traces, while plugin is considered stuck ---")
        id2name = dict([(th.ident, th.name) for th in threading.enumerate()])
        code = []
        for thread_id, stack in list(sys._current_frames().items()):  # pylint: disable=protected-access
            code.append(f"\n# Thread: {id2name.get(thread_id, '')}({thread_id})")
            for filename, lineno, name, line in traceback.extract_stack(stack):
                code.append(f'File: "{filename}", line {lineno}, in {name}')
                if line:
                    code.append(f"  {line.strip()}")
        log.info("\n".join(code))

    def terminate(self):
        self._terminate_sub_process()

    def _restart_sub_process(self):
        self._terminate_sub_process()
        self._make_sub_process()

    def _get_process_and_context(self):
        if not self.process or not self.process_context:
            self._make_sub_process()
        return self.process, self.process_context

    def execute(self, plugin_class, now, timeout):
        if self.profiling_log:
            timeout = None

        _, context = self._get_process_and_context()

        t0 = time.time()
        context.ns.plugin_class = plugin_class
        context.ns.now = now

        context.plugin_execution_finished_event.clear()
        context.plugin_execution_success_event.clear()

        context.plugin_ready_event.set()
        self.log.debug('Executor (main process) data exchange with plugin took %f sec', time.time() - t0)
        context.plugin_execution_finished_event.wait(timeout)

        db_corrupted = context.db_error_event.is_set()

        if db_corrupted:
            self._terminate_sub_process()
            try:
                recreator = PluginContext(self.config)
                recreator.recover_db()
            except BaseException as exception_during_recover:
                raise DbRecoverFailedException(exception_during_recover) from exception_during_recover
            self._make_sub_process()
            raise DbRecoveredException()

        in_time = context.plugin_execution_finished_event.is_set()
        if not in_time:
            os.kill(self.process.pid, signal.SIGUSR1)
            time.sleep(timeout / 2.0)
            self._restart_sub_process()
            raise PluginTimeoutException()

        success = context.plugin_execution_success_event.is_set()
        if not success:
            ex = context.ns.exception
            self._terminate_sub_process()
            if ex:
                raise PluginExecutionException(ex)
            else:
                raise PluginExecutionException()


__all__ = ['PluginExecutor', 'SameProcessPluginExecutor', 'SeparateProcessPluginExecutor',
           'PluginExecutionException', 'PluginTimeoutException', 'DbRecoveredException',
           'DbRecoverFailedException']