RuntimeError: can't start new thread

Describe the bug: We’re getting errors “RuntimeError: can’t start new thread”. The only change we’ve introduced is turning Elastic on. Since than we’re getting these errors. When running long enough, this exhausts the thread pool on the server.

To Reproduce

1. Use APM with Django

Expected behavior: To not run out of threads.

Environment (please complete the following information)

• OS: Ubuntu 16.04.5 LTS
• Python version: 3.5.2
• Framework and version [e.g. Django 2.1]: Django 1.11.20
• APM Server version: elastic cloud
• Agent version: elastic-apm 4.2.1

Additional context

RuntimeError: can’t start new thread File “threading.py”, line 1180, in run self.function(*self.args, **self.kwargs) File “elasticapm/transport/base.py”, line 124, in flush self._start_flush_timer() File “elasticapm/transport/base.py”, line 160, in _start_flush_timer self._flush_timer.start() File “threading.py”, line 844, in start _start_new_thread(self._bootstrap, ())

We’re running with celery and sentry.

• Agent config options

  Click to expand

  if env('ELASTIC_APM'):
  ELASTIC_APM = {
      # Set required service name. Allowed characters:
      # a-z, A-Z, 0-9, -, _, and space
      'SERVICE_NAME': 'CLIENT PRODUCTION',
      # Use if APM Server requires a token
      'SECRET_TOKEN': env('ELASTIC_APM_SECRET_TOKEN'),
      # Set custom APM Server URL (default: http://localhost:8200)
      'SERVER_URL': env('ELASTIC_APM_SERVER_URL)
  }
  
  INSTALLED_APPS += ('elasticapm.contrib.django',)
  # The Elastic APM tracing middleware needs to be first.
  MIDDLEWARE_CLASSES = (
      'elasticapm.contrib.django.middleware.TracingMiddleware',
      ) + MIDDLEWARE_CLASSES
  

[beniwohli]

I plan to do a release tomorrow 😃

[Kalanamith]

Issue still existst

/site-packages/elasticapm/metrics/base_metrics.py:104: in _start_collect_timer
    self._collect_timer.start()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <IntervalTimer(eapm metrics collect timer, initial daemon)>

    def start(self):
        """Start the thread's activity.
    
        It must be called at most once per thread object. It arranges for the
        object's run() method to be invoked in a separate thread of control.
    
        This method will raise a RuntimeError if called more than once on the
        same thread object.
    
        """
        if not self._initialized:
            raise RuntimeError("thread.__init__() not called")
    
        if self._started.is_set():
            raise RuntimeError("threads can only be started once")
        with _active_limbo_lock:
            _limbo[self] = self
        try:
>           _start_new_thread(self._bootstrap, ())
E           RuntimeError: can't start new thread