import os

import time

import weakref

from threading import Thread, Lock

import sentry_sdk

from sentry_sdk.utils import logger

from typing import TYPE_CHECKING

if TYPE_CHECKING:

from typing import Optional

MAX_DOWNSAMPLE_FACTOR = 10

class Monitor:

"""

Performs health checks in a separate thread once every interval seconds

and updates the internal state. Other parts of the SDK only read this state

and act accordingly.

"""

name = "sentry.monitor"

_thread: "Optional[Thread]"

_thread_for_pid: "Optional[int]"

def __init__(

self, transport: "sentry_sdk.transport.Transport", interval: float = 10

) -> None:

self.transport: "sentry_sdk.transport.Transport" = transport

self.interval: float = interval

self._healthy = True

self._downsample_factor: int = 0

self._running = True

self._reset_thread_state()

# See https://github.com/getsentry/sentry-python/issues/6148.

# If os.fork() runs while another thread holds self._thread_lock,

# the child inherits the lock locked but the holding thread does

# not exist in the child, so the lock can never be released and

# _ensure_running deadlocks forever. Reinitialise the lock and

# cached thread/pid in the child so it starts clean regardless

# of inherited state. We bind via a WeakMethod so the

# permanently-registered fork handler does not pin this Monitor

# (and its Transport): register_at_fork has no unregister API.

# POSIX-only; Windows uses spawn.

if hasattr(os, "register_at_fork"):

weak_reset = weakref.WeakMethod(self._reset_thread_state)

def _reset_in_child() -> None:

method = weak_reset()

if method is not None:

method()

os.register_at_fork(after_in_child=_reset_in_child)

def _reset_thread_state(self) -> None:

self._thread = None

self._thread_lock = Lock()

self._thread_for_pid = None

def _ensure_running(self) -> None:

"""

Check that the monitor has an active thread to run in, or create one if not.

Note that this might fail (e.g. in Python 3.12 it's not possible to

spawn new threads at interpreter shutdown). In that case self._running

will be False after running this function.

"""

if self._thread_for_pid == os.getpid() and self._thread is not None:

return None

with self._thread_lock:

if self._thread_for_pid == os.getpid() and self._thread is not None:

return None

def _thread() -> None:

while self._running:

time.sleep(self.interval)

if self._running:

self.run()

thread = Thread(name=self.name, target=_thread)

thread.daemon = True

try:

thread.start()

except RuntimeError:

# Unfortunately at this point the interpreter is in a state that no

# longer allows us to spawn a thread and we have to bail.

self._running = False

return None

self._thread = thread

self._thread_for_pid = os.getpid()

return None

def run(self) -> None:

self.check_health()

self.set_downsample_factor()

def set_downsample_factor(self) -> None:

if self._healthy:

if self._downsample_factor > 0:

logger.debug(

"[Monitor] health check positive, reverting to normal sampling"

)

self._downsample_factor = 0

else:

if self.downsample_factor < MAX_DOWNSAMPLE_FACTOR:

self._downsample_factor += 1

logger.debug(

"[Monitor] health check negative, downsampling with a factor of %d",

self._downsample_factor,

)

def check_health(self) -> None:

"""

Perform the actual health checks,

currently only checks if the transport is rate-limited.

TODO: augment in the future with more checks.

"""

self._healthy = self.transport.is_healthy()

def is_healthy(self) -> bool:

self._ensure_running()

return self._healthy

@property

def downsample_factor(self) -> int:

self._ensure_running()

return self._downsample_factor

def kill(self) -> None:

self._running = False