Merge pull request #1018 from plotly/debug-runner

Debug runner

Author: byronz

CHANGELOG.md

@@ -7,6 +7,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - [#967](https://github.com/plotly/dash/pull/967) Adds support for defining
 clientside JavaScript callbacks via inline strings.
 
+### Fixed
+- [#1018](https://github.com/plotly/dash/pull/1006) Fix the `dash.testing` **stop** API with process application runner in Python2. Use `kill()` instead of `communicate()` to avoid hanging.
+
 ## [1.6.1] - 2019-11-14
 ### Fixed
 - [#1006](https://github.com/plotly/dash/pull/1006) Fix IE11 / ES5 compatibility and validation issues

dash/testing/application_runners.py

@@ -95,6 +95,7 @@ def __exit__(self, exc_type, exc_val, traceback):
                         self.stop_timeout
                     )
                 )
+        logger.info("__exit__ complete")
 
     @property
     def url(self):
@@ -231,22 +232,25 @@ def start(
     def stop(self):
         if self.proc:
             try:
+                logger.info("proc.terminate with pid %s", self.proc.pid)
                 self.proc.terminate()
                 if utils.PY3:
                     # pylint:disable=no-member
                     _except = subprocess.TimeoutExpired
                     # pylint: disable=unexpected-keyword-arg
                     self.proc.communicate(timeout=self.stop_timeout)
                 else:
-                    _except = OSError
-                    self.proc.communicate()
+                    _except = Exception
+                    logger.info('ruthless kill the process to avoid zombie')
+                    self.proc.kill()
             except _except:
                 logger.exception(
                     "subprocess terminate not success, trying to kill "
                     "the subprocess in a safe manner"
                 )
                 self.proc.kill()
                 self.proc.communicate()
+        logger.info('process stop completes!')
 
 
 class RRunner(ProcessRunner):