managed VMs use threading even with threadsafe: false ? (python27, webapp2)

[Adam Sah]

Is anyone else seeing this?  I noticed that global variables were getting modified mid-execution and then confirmed by checking os.getpid() and saw the same process IDs in two concurrent requests (using time.sleep() to force concurrency)

Meanwhile, I drafted up a quick workaround - it seems to work, but I'd love a code review!

import logging

from os import getpid

from threading import Lock

from google.appengine.ext import webapp

from google.appengine.ext.webapp.util import run_wsgi_app

...

class SingleThreadedWSGIApplication(webapp.WSGIApplication):

  def __init__(self, *args, **kwargs):

    self.lock = Lock()

    super(SingleThreadedWSGIApplication, self).__init__(*args, **kwargs)

  def __call__(self, environ, start_response):

    logging.warning("SingleThreadedWSGIApplication.__call__().  pid=%d" % getpid())

    with self.lock:

      return super(SingleThreadedWSGIApplication, self).__call__(environ, start_response)

def is_production():

  ...bunch of custom environment checks...

PATHS=[ ... ]

app = SingleThreadedWSGIApplication(PATHS, debug=(not is_production()))

def main():

   ...

   run_wsgi_app(app)

if __name__ == "__main__":

  main()

relevant parts of app.yaml:

runtime: python-compat

vm: true

entrypoint: gunicorn -b :$PORT main:app

threadsafe: false

api_version: 1

instance_class: F4

[Adam (Cloud Platform Support)]

It's a known issue that Managed VMs don't respect 'threadsafe' and this is mentioned in an issue on GitHub, though these details are specific to the Java runtime. Regarding your workaround I don't see any issues with it.

[Adam Sah]

thanks!  would it be possible to copy the relevant "gotcha" issues to the core docs or have an "errata" page with workarounds?  I spent hours tracking this down, and it seems unreasonable to require new users (of Managed VMs) to read through every bug report... :-(

another example: Images API not supported yet....

thanks!

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[Adam (Cloud Platform Support)]

Yes, I can submit a request to the documentation team. You can also use the 'Send feedback' link at the top of any documentation page to submit feedback through the same channels.

On Monday, March 14, 2016 at 5:06:57 PM UTC-4, Adam Sah wrote:

thanks!  would it be possible to copy the relevant "gotcha" issues to the core docs or have an "errata" page with workarounds?  I spent hours tracking this down, and it seems unreasonable to require new users (of Managed VMs) to read through every bug report... :-(

another example: Images API not supported yet....

thanks!

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