Add Lambda header for invoking error. Closes #770.

moto/awslambda/models.py

@@ -138,6 +138,7 @@ class LambdaFunction(BaseModel):
         except Exception as ex:
             print("Exception %s", ex)
 
+        errored = False
         try:
             original_stdout = sys.stdout
             original_stderr = sys.stderr
@@ -152,26 +153,29 @@ class LambdaFunction(BaseModel):
             if exec_err:
                 result = "\n".join([exec_out.strip(), self.convert(exec_err)])
         except Exception as ex:
+            errored = True
             result = '%s\n\n\nException %s' % (mycode, ex)
         finally:
             codeErr.close()
             codeOut.close()
             sys.stdout = original_stdout
             sys.stderr = original_stderr
-        return self.convert(result)
+        return self.convert(result), errored
 
     def invoke(self, body, request_headers, response_headers):
         payload = dict()
 
         # Get the invocation type:
-        r = self._invoke_lambda(code=self.code, event=body)
+        res, errored = self._invoke_lambda(code=self.code, event=body)
         if request_headers.get("x-amz-invocation-type") == "RequestResponse":
-            encoded = base64.b64encode(r.encode('utf-8'))
+            encoded = base64.b64encode(res.encode('utf-8'))
             response_headers["x-amz-log-result"] = encoded.decode('utf-8')
             payload['result'] = response_headers["x-amz-log-result"]
-            result = r.encode('utf-8')
+            result = res.encode('utf-8')
         else:
             result = json.dumps(payload)
+        if errored:
+            response_headers['x-amz-function-error'] = "Handled"
 
         return result
 

tests/test_awslambda/test_lambda.py

@@ -432,3 +432,40 @@ def test_list_create_list_get_delete_list():
     conn.delete_function(FunctionName='testFunction')
 
     conn.list_functions()['Functions'].should.have.length_of(0)
+
+
+@mock_lambda
+def test_invoke_lambda_error():
+    lambda_fx = """
+    def lambda_handler(event, context):
+        raise Exception('failsauce')
+    """
+    zip_output = io.BytesIO()
+    zip_file = zipfile.ZipFile(zip_output, 'w', zipfile.ZIP_DEFLATED)
+    zip_file.writestr('lambda_function.zip', lambda_fx)
+    zip_file.close()
+    zip_output.seek(0)
+
+    client = boto3.client('lambda', region_name='us-east-1')
+    client.create_function(
+        FunctionName='test-lambda-fx',
+        Runtime='python2.7',
+        Role='test-iam-role',
+        Handler='lambda_function.lambda_handler',
+        Description='test lambda function',
+        Timeout=3,
+        MemorySize=128,
+        Publish=True,
+        Code={
+            'ZipFile': zip_output.read()
+        },
+    )
+
+    result = client.invoke(
+        FunctionName='test-lambda-fx',
+        InvocationType='RequestResponse',
+        LogType='Tail'
+    )
+
+    assert 'FunctionError' in result
+    assert result['FunctionError'] == 'Handled'