make sure we exit immediately if we fail to load the application.

While I'm here describe a more accurate error when it happens.

fix #508

gunicorn/arbiter.py

@@ -14,7 +14,7 @@ import sys
 import time
 import traceback
 
-from gunicorn.errors import HaltServer
+from gunicorn.errors import HaltServer, AppImportError
 from gunicorn.pidfile import Pidfile
 from gunicorn.sock import create_sockets
 from gunicorn import util
@@ -34,6 +34,9 @@ class Arbiter(object):
     # this error code, the arbiter will terminate.
     WORKER_BOOT_ERROR = 3
 
+    # A flag indicating if an application failed to be loaded
+    APP_LOAD_ERROR = 4
+
     START_CTX = {}
 
     LISTENERS = []
@@ -435,6 +438,9 @@ class Arbiter(object):
                     if exitcode == self.WORKER_BOOT_ERROR:
                         reason = "Worker failed to boot."
                         raise HaltServer(reason, self.WORKER_BOOT_ERROR)
+                    if exitcode == self.APP_LOAD_ERROR:
+                        reason = "App failed to load."
+                        raise HaltServer(reason, self.APP_LOAD_ERROR)
                     worker = self.WORKERS.pop(wpid, None)
                     if not worker:
                         continue
@@ -478,6 +484,13 @@ class Arbiter(object):
             sys.exit(0)
         except SystemExit:
             raise
+        except AppImportError as e:
+            self.log.debug("Exception while loading the application: \n%s",
+                    traceback.format_exc())
+
+            sys.stderr.write("%s\n" % e)
+            sys.stderr.flush()
+            sys.exit(self.APP_LOAD_ERROR)
         except:
             self.log.exception("Exception in worker process:\n%s",
                     traceback.format_exc())

gunicorn/errors.py

@@ -15,3 +15,7 @@ class HaltServer(BaseException):
 
 class ConfigError(BaseException):
     """ Exception raised on config error """
+
+
+class AppImportError(Exception):
+    """ Exception raised when loading an application """

gunicorn/util.py

@@ -18,6 +18,7 @@ import inspect
 import errno
 import warnings
 
+from gunicorn.errors import AppImportError
 from gunicorn.six import text_type, string_types
 
 MAXFD = 1024
@@ -358,11 +359,17 @@ def import_app(module):
             raise
 
     mod = sys.modules[module]
-    app = eval(obj, mod.__dict__)
+
+    try:
+        app = eval(obj, mod.__dict__)
+    except NameError:
+        raise AppImportError("Failed to find application: %r" % module)
+
     if app is None:
-        raise ImportError("Failed to find application object: %r" % obj)
+        raise AppImportError("Failed to find application object: %r" % obj)
+
     if not callable(app):
-        raise TypeError("Application object must be callable.")
+        raise AppImportError("Application object must be callable.")
     return app