Add more debugging for thorny multiprocessing issues

4 files changed, 15 insertions, 2 deletions

diff --git a/coverage/control.py b/coverage/control.py
index 32fb30c0..3464d66f 100644
--- a/coverage/control.py
+++ b/coverage/control.py
@@ -721,6 +721,8 @@ class Coverage(object):
 
     def _atexit(self):
         """Clean up on process shutdown."""
+        if self.debug and self.debug.should('dataio'):
+            self.debug.write("Inside _atexit: self._auto_save = %r" % (self._auto_save,))
         if self._started:
             self.stop()
         if self._auto_save:
diff --git a/coverage/data.py b/coverage/data.py
index 98b9c8a6..95b68881 100644
--- a/coverage/data.py
+++ b/coverage/data.py
@@ -144,6 +144,9 @@ class CoverageData(object):
         # A list of dicts of information about the coverage.py runs.
         self._runs = []
 
+        if self._debug and self._debug.should('dataio'):
+            self._debug.write("Creating CoverageData object")
+
     def __repr__(self):
         return "<{klass} lines={lines} arcs={arcs} tracers={tracers} runs={runs}>".format(
             klass=self.__class__.__name__,
diff --git a/coverage/multiproc.py b/coverage/multiproc.py
index 78c680c7..fe837318 100644
--- a/coverage/multiproc.py
+++ b/coverage/multiproc.py
@@ -34,12 +34,18 @@ class ProcessWithCoverage(OriginalProcess):
         rcfile = os.environ[COVERAGE_RCFILE_ENV]
         cov = Coverage(data_suffix=True, config_file=rcfile)
         cov.start()
+        debug = cov.debug
         try:
+            if debug.should("multiproc"):
+                debug.write("Calling multiprocessing bootstrap")
             return original_bootstrap(self)
         finally:
+            if debug.should("multiproc"):
+                debug.write("Finished multiprocessing bootstrap")
             cov.stop()
             cov.save()
-
+            if debug.should("multiproc"):
+                debug.write("Saved multiprocessing data")
 
 class Stowaway(object):
     """An object to pickle, so when it is unpickled, it can apply the monkey-patch."""
diff --git a/tests/test_data.py b/tests/test_data.py
index 52702e97..4bccdcf2 100644
--- a/tests/test_data.py
+++ b/tests/test_data.py
@@ -554,7 +554,9 @@ class CoverageDataFilesTest(DataTestHelpers, CoverageTest):
 
         self.assertRegex(
             debug.get_output(),
-            r"^Writing data to '.*\.coverage'\n"
+            r"^Creating CoverageData object\n"
+            r"Writing data to '.*\.coverage'\n"
+            r"Creating CoverageData object\n"
             r"Reading data from '.*\.coverage'\n$"
         )