Merge commit 'f40d39b'

tornado/concurrent.py

@@ -29,6 +29,7 @@
 
 from tornado.stack_context import ExceptionStackContext, wrap
 from tornado.util import raise_exc_info, ArgReplacer
+from tornado.log import app_log
 
 try:
     from concurrent import futures
@@ -173,8 +174,11 @@ def _check_done(self):
     def _set_done(self):
         self._done = True
         for cb in self._callbacks:
-            # TODO: error handling
-            cb(self)
+            try:
+                cb(self)
+            except Exception:
+                app_log.exception('exception calling callback %r for %r',
+                                  cb, self)
         self._callbacks = None
 
 TracebackFuture = Future

tornado/gen.py

@@ -109,7 +109,10 @@ def final_callback(future):
                 raise ReturnValueIgnoredError(
                     "@gen.engine functions cannot return values: %r" %
                     (future.result(),))
-        future.add_done_callback(final_callback)
+        # The engine interface doesn't give us any way to return
+        # errors but to raise them into the stack context.
+        # Save the stack context here to use when the Future has resolved.
+        future.add_done_callback(stack_context.wrap(final_callback))
     return wrapper