Adds DEBUG to print Zappa errors in 500 messages

README.md

@@ -101,6 +101,8 @@ to change Zappa's behavior. Use these at your own risk!
  {
     "dev": {
         "aws_region": "us-east-1", // AWS Region (default US East),
+        "debug": true // Print Zappa configuration errors tracebacks in the 500
+        "delete_zip": true // Delete the local zip archive after code updates
         "domain": "yourapp.yourdomain.com", // Required if you're using a domain
         "http_methods": ["GET", "POST"], // HTTP Methods to route,
         "integration_response_codes": [200, 301, 404, 500], // Integration response status codes to route

test_settings.json

@@ -2,6 +2,7 @@
     "ttt333": {
        "s3_bucket": "lmbda",
        "app_function": "tests.test_app.hello_world",
-       "delete_zip": true 
+       "delete_zip": true,
+       "debug": true 
     }
 }

test_settings.py

@@ -1,3 +1,4 @@
 APP_MODULE = 'tests.test_app'
 APP_FUNCTION = 'hello_world'
-SCRIPT_NAME = 'hello_world'
+DEBUG = 'True'
+SCRIPT_NAME = 'hello_world'

zappa/cli.py

@@ -48,6 +48,7 @@ class ZappaCLI(object):
     api_stage = None
     app_function = None
     aws_region = None
+    debug = None
     project_name = None
     lambda_name = None
     s3_bucket_name = None
@@ -283,6 +284,8 @@ def load_settings(self, settings_file="zappa_settings.json", session=None):
             self.api_stage].get('app_function', None)
         self.aws_region = self.zappa_settings[
             self.api_stage].get('aws_region', 'us-east-1')
+        self.debug = self.zappa_settings[
+            self.api_stage].get('debug', True)
 
         # Create an Zappa object..
         self.zappa = Zappa(session)
@@ -326,6 +329,9 @@ def create_package(self):
             app_module, app_function = self.app_function.rsplit('.', 1)
             settings_s = "# Generated by Zappa\nAPP_MODULE='%s'\nAPP_FUNCTION='%s'\n" % (app_module, app_function)
 
+            if self.debug is not None:
+                settings_s = settings_s + "DEBUG='%s'" % (self.debug) # Cast to Bool in handler
+
             # Lambda requires a specific chmod
             temp_settings = tempfile.NamedTemporaryFile(delete=False)
             os.chmod(temp_settings.name, 0644)

zappa/handler.py

@@ -5,6 +5,7 @@
 import importlib
 import logging
 import os
+import traceback
 
 from urllib import urlencode
 from StringIO import StringIO
@@ -24,6 +25,9 @@
 logger = logging.getLogger()
 logger.setLevel(logging.INFO)
 
+class LambdaException(Exception):
+    pass
+
 class LambdaHandler(object):
     """
     Singleton for avoiding duplicate setup.
@@ -58,80 +62,100 @@ def handler(self, event, context):
         
         """
 
-        time_start = datetime.datetime.now()
-
-        settings = self.settings
-
-        # The app module
-        app_module = importlib.import_module(settings.APP_MODULE)
-
-        # The application
-        app_function = getattr(app_module, settings.APP_FUNCTION)
-
-        app = ZappaWSGIMiddleware(app_function)
-
-        # This is a normal HTTP request
-        if event.get('method', None):
-            # If we just want to inspect this,
-            # return this event instead of processing the request
-            # https://your_api.aws-api.com/?event_echo=true
-            event_echo = getattr(settings, "EVENT_ECHO", True)
-            if event_echo:
-                if 'event_echo' in list(event['params'].values()):
-                    return {'Content': str(event) + '\n' + str(context), 'Status': 200}
-
-            # Create the environment for WSGI and handle the request
-            environ = create_wsgi_request(event, script_name='',
-                                          trailing_slash=False)
-
-            # We are always on https on Lambda, so tell our wsgi app that.
-            environ['wsgi.url_scheme'] = 'https'
-
-            response = Response.from_app(app, environ)
-
-            zappa_returndict = dict()
-
-            if response.data:
-                zappa_returndict['Content'] = response.data
-
-            # Pack the WSGI response into our special dictionary.
-            for (header_name, header_value) in response.headers:
-                zappa_returndict[header_name] = header_value
-            zappa_returndict['Status'] = response.status_code
-
-            # To ensure correct status codes, we need to
-            # pack the response as a deterministic B64 string and raise it
-            # as an error to match our APIGW regex.
-            # The DOCTYPE ensures that the page still renders in the browser.
-            exception = None
-            if response.status_code in [400, 401, 403, 404, 500]:
-                content = "<!DOCTYPE html>" + str(response.status_code) + response.data
+        try:
+            time_start = datetime.datetime.now()
+
+            settings = self.settings
+
+            # The app module
+            app_module = importlib.import_module(settings.APP_MODULE)
+
+            # The application
+            app_function = getattr(app_module, settings.APP_FUNCTION)
+
+            app = ZappaWSGIMiddleware(app_function)
+
+            # This is a normal HTTP request
+            if event.get('method', None):
+                # If we just want to inspect this,
+                # return this event instead of processing the request
+                # https://your_api.aws-api.com/?event_echo=true
+                event_echo = getattr(settings, "EVENT_ECHO", True)
+                if event_echo:
+                    if 'event_echo' in list(event['params'].values()):
+                        return {'Content': str(event) + '\n' + str(context), 'Status': 200}
+
+                # Create the environment for WSGI and handle the request
+                environ = create_wsgi_request(event, script_name='',
+                                              trailing_slash=False)
+
+                # We are always on https on Lambda, so tell our wsgi app that.
+                environ['wsgi.url_scheme'] = 'https'
+
+                # Execute the application
+                response = Response.from_app(app, environ)
+
+                # This is the object we're going to return.
+                zappa_returndict = dict()
+
+                if response.data:
+                    zappa_returndict['Content'] = response.data
+
+                # Pack the WSGI response into our special dictionary.
+                for (header_name, header_value) in response.headers:
+                    zappa_returndict[header_name] = header_value
+                zappa_returndict['Status'] = response.status_code
+
+                # To ensure correct status codes, we need to
+                # pack the response as a deterministic B64 string and raise it
+                # as an error to match our APIGW regex.
+                # The DOCTYPE ensures that the page still renders in the browser.
+                exception = None
+                if response.status_code in [400, 401, 403, 404, 500]:
+                    content = "<!DOCTYPE html>" + str(response.status_code) + response.data
+                    exception = base64.b64encode(content)
+                # Internal are changed to become relative redirects
+                # so they still work for apps on raw APIGW and on a domain.
+                elif response.status_code in [301, 302]:
+                    # Location is by default relative on Flask. Location is by default
+                    # absolute on Werkzeug. We can set autocorrect_location_header on
+                    # the response to False, but it doesn't work. We have to manually
+                    # remove the host part.
+                    location = response.location
+                    hostname = 'https://' + environ['HTTP_HOST']
+                    if location.startswith(hostname):
+                        exception = location[len(hostname):]
+
+                # Calculate the total response time,
+                # and log it in the Common Log format.
+                time_end = datetime.datetime.now()
+                delta = time_end - time_start
+                response_time_ms = delta.total_seconds() * 1000
+                response.content = response.data
+                common_log(environ, response, response_time=response_time_ms)
+
+                # Finally, return the response to API Gateway.
+                if exception: # pragma: no cover
+                    raise LambdaException(exception)
+                else:
+                    return zappa_returndict
+        except LambdaException as e: # pragma: nocover
+            raise e
+        except Exception as e: # pragma: nocover
+
+            # Print statements are visible in the logs either way
+            print(e)
+
+            # Print the error to the browser upon failure?
+            debug = bool(getattr(app_module, settings.DEBUG, True))
+            if debug:
+                # Return this unspecified exception as a 500.
+                content = "<!DOCTYPE html>500. From Zappa: <pre>" + str(e) + "</pre><br /><pre>" + traceback.format_exc().replace('\n', '<br />') + "</pre>"
                 exception = base64.b64encode(content)
-            # Internal are changed to become relative redirects
-            # so they still work for apps on raw APIGW and on a domain.
-            elif response.status_code in [301, 302]:
-                # Location is by default relative on Flask. Location is by default
-                # absolute on Werkzeug. We can set autocorrect_location_header on
-                # the response to False, but it doesn't work. We have to manually
-                # remove the host part.
-                location = response.location
-                hostname = 'https://' + environ['HTTP_HOST']
-                if location.startswith(hostname):
-                    exception = location[len(hostname):]
-
-            # Calculate the total response time,
-            # and log it in the Common Log format.
-            time_end = datetime.datetime.now()
-            delta = time_end - time_start
-            response_time_ms = delta.total_seconds() * 1000
-            response.content = response.data
-            common_log(environ, response, response_time=response_time_ms)
-
-            # Finally, return the response to API Gateway.
-            if exception: # pragma: no cover
                 raise Exception(exception)
             else:
-                return zappa_returndict
+                raise e
+
 
 def lambda_handler(event, context): # pragma: no cover
     return LambdaHandler.lambda_handler(event, context)