add test case

ddtrace/internal/module.py

@@ -278,6 +278,13 @@ def __delitem__(self, name):
 
     def __getattribute__(self, name):
         # type: (str) -> Any
+        if PY2 and name == "keys":
+            # This is a potential attempt to make a copy of sys.modules using
+            # dict(sys.modules), so we take this change to update self to look
+            # like sys.modules.
+            super(ModuleWatchdog, self).clear()
+            super(ModuleWatchdog, self).update(self._modules)
+
         try:
             return super(ModuleWatchdog, self).__getattribute__("_modules").__getattribute__(name)
         except AttributeError:
@@ -308,7 +315,15 @@ def find_module(self, fullname, path=None):
                 if not isinstance(loader, _ImportHookChainedLoader):
                     loader = _ImportHookChainedLoader(loader)
 
-                loader.add_callback(type(self), self.after_import)
+                if PY2:
+                    # With Python 2 we don't get all the finder invoked, so we
+                    # make sure we register all the callbacks at the earliest
+                    # opportunity.
+                    for finder in sys.meta_path:
+                        if isinstance(finder, ModuleWatchdog):
+                            loader.add_callback(type(finder), finder.after_import)
+                else:
+                    loader.add_callback(type(self), self.after_import)
 
                 return loader
 

riotfile.py

@@ -246,6 +246,7 @@ def select_pys(min_version=MIN_PYTHON_VERSION, max_version=MAX_PYTHON_VERSION):
                         "structlog": latest,
                         # httpretty v1.0 drops python 2.7 support
                         "httpretty": "==0.9.7",
+                        "gevent": latest,
                     },
                 )
             ],

tests/tracer/test_forksafe.py

@@ -1,4 +1,5 @@
 import os
+import sys
 
 import pytest
 import six
@@ -285,3 +286,59 @@ def fn():
     pid, status = os.waitpid(child, 0)
     exit_code = os.WEXITSTATUS(status)
     assert exit_code == 42
+
+
+@pytest.mark.subprocess(
+    out="C\nT\nC\nT\nC\nT\n" if sys.platform == "darwin" else "C\nC\nC\nT\nT\nT\n",
+    err=None,
+)
+def test_gevent_reinit_patch():
+    import os
+    import sys
+
+    from ddtrace.internal import forksafe
+    from ddtrace.internal.periodic import PeriodicService
+
+    class TestService(PeriodicService):
+        def __init__(self):
+            super(TestService, self).__init__(interval=1.0)
+
+        def periodic(self):
+            print("T")
+
+    service = TestService()
+    service.start()
+
+    def restart_service():
+        global service
+
+        service.stop()
+        service = TestService()
+        service.start()
+
+    forksafe.register(restart_service)
+
+    import gevent  # noqa
+
+    def run_child():
+        global service
+
+        # We mimic what gunicorn does in child processes
+        gevent.monkey.patch_all()
+        gevent.hub.reinit()
+
+        print("C")
+
+        gevent.sleep(1.1)
+
+        service.stop()
+
+    def fork_workers(num):
+        for _ in range(num):
+            if os.fork() == 0:
+                run_child()
+                sys.exit(0)
+
+    fork_workers(3)
+
+    service.stop()