Include timestamp in error output. Fixes #137.

changelog.rst

@@ -57,6 +57,8 @@
   longer print the entire WSGI environment by default. This avoids
   possible information disclosure vulnerabilities. Originally reported
   in :pr:`779` by sean-peters-au and changed in :pr:`781`.
+- Unhandled exception reports that kill a greenlet print now include a
+  timestamp. See :issue:`137`.
 
 1.1.0 (Mar 5, 2016)
 ===================

gevent/_util.py

@@ -69,3 +69,38 @@ def copy_globals(source,
             del globs['copy_globals']
 
     return copied
+
+class Lazy(object):
+    """
+    A non-data descriptor used just like @property. The
+    difference is the function value is assigned to the instance
+    dict the first time it is accessed and then the function is never
+    called agoin.
+    """
+    def __init__(self, func):
+        self.data = (func, func.__name__)
+
+    def __get__(self, inst, class_):
+        if inst is None:
+            return self
+
+        func, name = self.data
+        value = func(inst)
+        inst.__dict__[name] = value
+        return value
+
+class readproperty(object):
+    """
+    A non-data descriptor like @property. The difference is that
+    when the property is assigned to, it is cached in the instance
+    and the function is not called on that instance again.
+    """
+
+    def __init__(self, func):
+        self.func = func
+
+    def __get__(self, inst, class_):
+        if inst is None:
+            return self
+
+        return self.func(inst)

gevent/greenlet.py

@@ -5,6 +5,7 @@ from greenlet import greenlet
 from gevent._compat import PY3
 from gevent._compat import PYPY
 from gevent._compat import reraise
+from gevent._util import Lazy
 from gevent._tblib import dump_traceback
 from gevent._tblib import load_traceback
 from gevent.hub import GreenletExit
@@ -86,22 +87,6 @@ class FailureSpawnedLink(SpawnedLink):
         if not source.successful():
             return SpawnedLink.__call__(self, source)
 
-
-class _lazy(object):
-
-    def __init__(self, func):
-        self.data = (func, func.__name__)
-
-    def __get__(self, inst, class_):
-        if inst is None:
-            return self
-
-        func, name = self.data
-        value = func(inst)
-        inst.__dict__[name] = value
-        return value
-
-
 class Greenlet(greenlet):
     """A light-weight cooperatively-scheduled execution unit.
     """
@@ -163,7 +148,7 @@ class Greenlet(greenlet):
     def kwargs(self):
         return self._kwargs or {}
 
-    @_lazy
+    @Lazy
     def _links(self):
         return deque()
 

gevent/hub.py

@@ -29,6 +29,7 @@ __all__ = [
 from gevent._compat import string_types
 from gevent._compat import xrange
 from gevent._util import _NONE
+from gevent._util import readproperty
 
 if sys.version_info[0] <= 2:
     import thread # pylint:disable=import-error
@@ -567,14 +568,38 @@ class Hub(RawGreenlet):
                 if cb is not None:
                     cb.stop()
 
+    @readproperty
+    def exception_stream(self):
+        """
+        The stream to which exceptions will be written.
+        Defaults to ``sys.stderr`` unless assigned to.
+
+        .. versionadded:: 1.2a1
+        """
+
+        return sys.stderr
+
     def print_exception(self, context, type, value, tb):
         # Python 3 does not gracefully handle None value or tb in
         # traceback.print_exception() as previous versions did.
+        # pylint:disable=no-member
+        errstream = self.exception_stream
+
         if value is None:
-            sys.stderr.write('%s\n' % type.__name__)
+            errstream.write('%s\n' % type.__name__)
         else:
-            traceback.print_exception(type, value, tb)
+            traceback.print_exception(type, value, tb, file=errstream)
         del tb
+
+        try:
+            import time
+            errstream.write(time.ctime())
+            errstream.write(' ' if context is not None else '\n')
+        except: # pylint:disable=bare-except
+            # Possible not safe to import under certain
+            # error conditions in Python 2
+            pass
+
         if context is not None:
             if not isinstance(context, str):
                 try:
@@ -582,7 +607,7 @@ class Hub(RawGreenlet):
                 except: # pylint:disable=bare-except
                     traceback.print_exc()
                     context = repr(context)
-            sys.stderr.write('%s failed with %s\n\n' % (context, getattr(type, '__name__', 'exception'), ))
+            errstream.write('%s failed with %s\n\n' % (context, getattr(type, '__name__', 'exception'), ))
 
     def switch(self):
         switch_out = getattr(getcurrent(), 'switch_out', None)