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# Module for logging in subprocess. Process related info (call stack) is logged
# to simplify investigation of main process hangings
#
# Copyright © Cloud Linux GmbH & Cloud Linux Software, Inc 2010-2024 All Rights Reserved
#
# Licensed under CLOUD LINUX LICENSE AGREEMENT
# http://cloudlinux.com/docs/LICENSE.TXT
import atexit
import collections
import dataclasses
import logging
import logging.handlers
import os
import pathlib
import queue
import time
from datetime import datetime
from multiprocessing import Event, Process, Queue

from raven.handlers.logging import SentryHandler
import psutil

from lve_utils.sentry import init_lve_utils_sentry_client

# NOTE: set records history size relatively small,
#       otherwise sentry will trim the log message with history records and process ancestors
DEFAULT_RECORDS_HISTORY_SIZE = 10
DEFAULT_LOG_EVENTS_TIMEOUT = 300
DEFAULT_LOG_FORMAT = '%(asctime)s - %(name)s - %(levelname)s - %(message)s'


@dataclasses.dataclass
class ProcessDescription:
    """
    Process description object

    pid: int - process id
    ppid: int | None - parent process id
    user: str | None - process owner
    status: str | None - process status
    start_time: datetime | None - process start time
    cmdline: str | None - process command line
    """

    pid: int
    ppid: int | None
    user: str | None
    status: str | None
    start_time: datetime | None
    cmdline: str | None

    @classmethod
    def from_psutil(cls, process: psutil.Process):
        """Build process description object using psutil.Process object"""
        try:
            ppid = process.ppid()
        except Exception:
            ppid = None
        try:
            cmdline = ' '.join(process.cmdline())
        except Exception:
            cmdline = None
        try:
            start_time = datetime.fromtimestamp(process.create_time())
        except Exception:
            start_time = None
        try:
            user = process.username()
        except Exception:
            user = None
        try:
            status = process.status()
        except Exception:
            status = None
        return cls(process.pid, ppid, user, status, start_time, cmdline)

    def to_str(self):
        return f"PID: {self.pid}, PPID: {self.ppid}, User: {self.user}, Status: {self.status} " \
            f"Start time: {self.start_time} Command: {self.cmdline}"


class QueueListenerWithHistory(logging.handlers.QueueListener):
    def __init__(
            self,
            queue,
            *handlers,
            timeout: int = DEFAULT_LOG_EVENTS_TIMEOUT,
            records_history_size: int = DEFAULT_RECORDS_HISTORY_SIZE,
    ):
        """Queue listener with log records history

        :param multiprocessing.Queue queue: log records queue
        :param int timeout: log records flow timeout, defaults to DEFAULT_LOG_EVENTS_TIMEOUT
                            In case timeput is reached, last log records and process ancestors are logged
        :param int records_history_size: the max number of records to log in case of timeout
        """
        super().__init__(queue, *handlers, respect_handler_level=True)
        self._records_history_queue: collections.deque[logging.LogRecord] = collections.deque(
            iterable=[],
            maxlen=records_history_size
        )
        self._timeout = timeout
        self._timout_registred = False

    def dequeue(self, _block):
        """Dequeue log event"""
        while True:
            try:
                record = self.queue.get(timeout=self._timeout)
                self._records_history_queue.append(record)
                break
            except queue.Empty:
                self._handle_queue_timeout()
        return record

    def _monitor(self):
        """Main loop to process log events"""
        self._handle_monitor_started()
        super()._monitor()
        self._handle_monitor_finished()

    def _handle_monitor_started(self):
        """Start monitoring log events processing time"""
        self._start_ts = time.time()

    def _handle_monitor_finished(self):
        """Log that monitor finished processing log records"""
        if self._timout_registred is True:
            r = self._create_record(
                logging.ERROR,
                'Processing log queue took %.4f seconds. Pid: %s',
                time.time() - self._start_ts,
                os.getpid(),
            )
            self.handle(r)

    def _get_ancestors(self):
        """Collect process ancestors up to pid 1"""
        ancestors: list[ProcessDescription] = []
        try:
            process = psutil.Process()
            ancestors = [ProcessDescription.from_psutil(process)]
            while (ppid := process.ppid()) != 0:
                process = psutil.Process(ppid)
                ancestors.append(ProcessDescription.from_psutil(process))
            return ancestors
        except Exception:
            return ancestors

    def _create_record(self, level, msg, *args):
        """Create log record"""
        return logging.LogRecord(
            name=__name__,
            level=level,
            pathname='',
            lineno=1,
            msg=msg,
            args=args,
            exc_info=None,
        )

    def _handle_queue_timeout(self):
        """
        Handle log queue timeout event.
        Print last events (incl. omitted because debug disabled) and process ancestors to log.
        """
        if self._timout_registred is False:
            proc_ancestors = '\n'.join(
                proc_descr.to_str() for proc_descr in self._get_ancestors()[::-1]
            )
            last_events = '\n'.join(
                f'[{record.levelname}] - {datetime.fromtimestamp(record.created)}: {record.message}'
                for record in self._records_history_queue
            )
            error_msg = 'Log queue timeout. Last events:\n%s\nProcess ancestors:\n%s'
            error_args = (last_events, proc_ancestors)
            r = self._create_record(logging.ERROR, error_msg, *error_args)
            self.handle(r)
            self._timout_registred = True


def get_log_level(file_name: str):
    """Get log level based on debug flag presence"""
    return logging.DEBUG if pathlib.Path(f'{file_name}.debug.flag').exists() else logging.INFO


def run_subpprocess_logger(q: Queue, stop_event: Event, file_name: str, timeout: int):
    """
    Main function to process log events in subprocess

    :param Queue q: log records queue
    :param Event stop_event: stop event
    :param str file_name: log file name
    """
    sentry_handler = SentryHandler(init_lve_utils_sentry_client('lvectl'), level=logging.ERROR)

    fh = logging.FileHandler(file_name)
    fh.setFormatter(logging.Formatter(DEFAULT_LOG_FORMAT))
    fh.setLevel(get_log_level(file_name))

    q_handler = QueueListenerWithHistory(q, fh, sentry_handler, timeout=timeout)
    q_handler.start()
    stop_event.wait()
    q_handler.stop()


@dataclasses.dataclass
class SubprocessLogger:
    logger_process: Process
    stop_event: Event


subprocess_loggers: dict[str | None, SubprocessLogger] = {}


def init_subprocess_logger(
    logger_name: str | None,
    file_name: str,
    timeout: int = DEFAULT_LOG_EVENTS_TIMEOUT,
) -> logging.Logger:
    """
    Get asynchronous logger running in subprocess

    Log records asynchronously in subprocess (>=info by default, >= debug when debug flag is present).
    Log records from debug and higher in subprocess in case of timeout.

    WARNING: multiprocessing.Queue is used to pass log records. It works asynchornously
             (passing to subprocess in handled by separate thread). This may lead to log records not
             being passed to the subprocess in case main process got stuck e.g. in kmodlve kernel space.

    :param str | None logger_name: logger name
    :param str file_name: log file
    :param int timeout: log events processing timeout
    """
    global subprocess_loggers
    subprocess_logger = subprocess_loggers.get(logger_name)
    if subprocess_logger is not None:
        return logging.getLogger(logger_name)

    logger = logging.getLogger(logger_name)
    # NOTE: We want to pass all the records (incl. debug) to the subprocess
    #       so that we can log them in case of timeout
    logger.setLevel(logging.DEBUG)

    subprocess_logger_queue: Queue = Queue()
    queue_handler = logging.handlers.QueueHandler(subprocess_logger_queue)
    queue_handler.setLevel(logging.DEBUG)
    logger.addHandler(queue_handler)

    stop_event = Event()
    logger_process = Process(target=run_subpprocess_logger,
                             args=(subprocess_logger_queue, stop_event, file_name, timeout))
    logger_process.start()
    atexit.register(stop_event.set)
    subprocess_loggers[logger_name] = SubprocessLogger(logger_process, stop_event)

    return logger


def stop_subprocess_logger(name: str):
    """
    Stop subprocess logger
    """
    global subprocess_loggers
    subprocess_logger = subprocess_loggers.get(name)
    if subprocess_logger is None:
        return

    subprocess_logger.stop_event.set()
    subprocess_logger.logger_process.join()
    del subprocess_loggers[name]