Cannot run Google App Engine custom managed VM: --custom-entrypoint must be set error

Question

PROBLEM DESCRIPTION

I am trying to create a custom managed VM for Google App Engine that behaves identically to the standard python27 managed VM pro

Answer 1

EDIT 1: The solution posted by user862857 makes use of Docker itself to build images from the Dockerfile and run them in containers. This is also a good approach to running Managed VMs and Custom Runtimes in development contexts.

---

The accepted answer doesn't seem correct. A github README should not trump the official docs for authoritativeness when dealing with a rapidly-evolving Beta product. It's perfectly possible to a runtime: custom app in the dev environment, using the Dockerfile mentioned in OP's post,

FROM gcr.io/google_appengine/python-compat
ADD . /app

using the --runtime=python-compat flag. They would need to catch requests to /_ah/start and /_ah/health, though. Attempt to run the following command, given the following files, and see for yourself:

devserver command

$ dev_appserver.py app.yaml --runtime=python-compat

app.yaml

runtime: custom
vm: true
api_version: 1
threadsafe: true

handlers:
- url: /.*
  script: main.app

Dockerfile

FROM gcr.io/google_appengine/python-compat

RUN apt-get update

RUN apt-get install -y gwhois

ADD . /app

main.py

import logging
import webapp2
from subprocess import Popen, PIPE

class OkHandler (webapp2.RequestHandler):
    def get (self): 
        self.response.write ('ok')

class MainPage(webapp2.RequestHandler):
    def get(self):
        self.response.headers['Content-Type'] = 'text/plain'
        domain = self.request.get ('domain')
        cmd = ["gwhois", domain]
        process = Popen (cmd, stdout=PIPE, stderr=PIPE)
        output, err = process.communicate()
        exit_code = process.wait()
        self.response.write('stdout: %s' % output)
        logging.info ('stderr: %s' % err)

app = webapp2.WSGIApplication([
    ('/', MainPage),
    ('/_ah/start', OkHandler),
    ('/_ah/health', OkHandler)
], debug=True)

Send a request to /?domain=stackoverflow.com to see this in action.

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N.B.

If they wished to entirely decouple from the python-compat runtime and simply deploy/test a python WSGI app via, they could also use the --custom_entrypoint flag, so long as they had a command which would start running the appropriate WSGI app on a suitable port (such a command would be uwsgi or gunicorn).