Allow User Defined Exceptions

doc/source/python/python_component.md

@@ -164,6 +164,64 @@ If you want more control you can provide a low-level methods that will provide a
     def aggregate_raw(self, msgs: prediction_pb2.SeldonMessageList) -> prediction_pb2.SeldonMessage:
 ```
 
+## User Defined Exceptions
+If you want to handle custom exceptions define a field `model_error_handler` as shown below:
+```
+    model_error_handler = flask.Blueprint('error_handlers', __name__)
+```
+An example is as follow:
+
+```python
+"""
+Model Template
+"""
+class MyModel(Object):
+
+    """
+    The field is used to register custom exceptions
+    """
+    model_error_handler = flask.Blueprint('error_handlers', __name__)
+
+    """
+    Register the handler for an exception
+    """
+    @model_error_handler.app_errorhandler(UserCustomException)
+    def handleCustomError(error):
+        response = jsonify(error.to_dict())
+        response.status_code = error.status_code
+        return response
+
+    def __init__(self, metrics_ok=True, ret_nparray=False, ret_meta=False):
+        pass
+
+    def predict(self, X, features_names, **kwargs):
+        raise UserCustomException('Test-Error-Msg',1402,402)
+        return X
+```
+
+```python
+"""
+User Defined Exception
+"""
+class UserCustomException(Exception):
+
+    status_code = 404
+
+    def __init__(self, message, application_error_code,http_status_code):
+        Exception.__init__(self)
+        self.message = message
+        if http_status_code is not None:
+            self.status_code = http_status_code
+        self.application_error_code = application_error_code
+
+    def to_dict(self):
+        rv = {"status": {"status": self.status_code, "message": self.message,
+                         "app_code": self.application_error_code}}
+        return rv
+
+```
+
+
 ## Next Steps
 
 After you have created the Component you need to create a Docker image that can be managed by Seldon Core. Follow the documentation to do this with [s2i](./python_wrapping_s2i.md) or [Docker](./python_wrapping_docker.md).

python/seldon_core/wrapper.py

@@ -19,6 +19,10 @@ def get_rest_microservice(user_model):
     app = Flask(__name__, static_url_path='')
     CORS(app)
 
+    if hasattr(user_model, 'model_error_handler'):
+        logger.info('Registering the custom error handler...')
+        app.register_blueprint(user_model.model_error_handler)
+
     @app.errorhandler(SeldonMicroserviceException)
     def handle_invalid_usage(error):
         response = jsonify(error.to_dict())

python/tests/test_application_exception_microservice.py

@@ -0,0 +1,93 @@
+import json
+import numpy as np
+from google.protobuf import json_format
+import base64
+import tensorflow as tf
+from tensorflow.core.framework.tensor_pb2 import TensorProto
+
+from seldon_core.wrapper import get_rest_microservice, SeldonModelGRPC, get_grpc_server
+from seldon_core.proto import prediction_pb2
+from seldon_core.user_model import SeldonComponent
+
+import flask
+from flask import jsonify
+
+class UserCustomException(Exception):
+    status_code = 404
+
+    def __init__(self, message, application_error_code,http_status_code):
+        Exception.__init__(self)
+        self.message = message
+        if http_status_code is not None:
+            self.status_code = http_status_code
+        self.application_error_code = application_error_code
+
+    def to_dict(self):
+        rv = {"status": {"status": self.status_code, "message": self.message,
+                         "app_code": self.application_error_code}}
+        return rv
+
+class UserObject(SeldonComponent):
+
+    model_error_handler = flask.Blueprint('error_handlers', __name__)
+
+    @model_error_handler.app_errorhandler(UserCustomException)
+    def handleCustomError(error):
+        response = jsonify(error.to_dict())
+        response.status_code = error.status_code
+        return response
+
+
+    def __init__(self, metrics_ok=True, ret_nparray=False, ret_meta=False):
+        self.metrics_ok = metrics_ok
+        self.ret_nparray = ret_nparray
+        self.nparray = np.array([1, 2, 3])
+        self.ret_meta = ret_meta
+
+    def predict(self, X, features_names, **kwargs):
+        raise UserCustomException('Test-Error-Msg',1402,402)
+        return X
+
+
+class UserObjectLowLevel(SeldonComponent):
+
+    model_error_handler = flask.Blueprint('error_handlers', __name__)
+
+    @model_error_handler.app_errorhandler(UserCustomException)
+    def handleCustomError(error):
+        response = jsonify(error.to_dict())
+        response.status_code = error.status_code
+        return response
+
+
+    def __init__(self, metrics_ok=True, ret_nparray=False):
+        self.metrics_ok = metrics_ok
+        self.ret_nparray = ret_nparray
+        self.nparray = np.array([1, 2, 3])
+
+    def predict_rest(self, request):
+        raise UserCustomException('Test-Error-Msg',1402,402)
+        return {"data": {"ndarray": [9, 9]}}
+
+
+def test_raise_exception():
+    user_object = UserObject()
+    app = get_rest_microservice(user_object)
+    client = app.test_client()
+    rv = client.get('/predict?json={"data":{"names":["a","b"],"ndarray":[[1,2]]}}')
+    j = json.loads(rv.data)
+    print(j)
+    assert rv.status_code == 402
+    assert j["status"]["app_code"] == 1402
+
+
+def test_raise_eception_lowlevel():
+    user_object = UserObjectLowLevel()
+    app = get_rest_microservice(user_object)
+    client = app.test_client()
+    rv = client.get('/predict?json={"data":{"ndarray":[1,2]}}')
+    j = json.loads(rv.data)
+    print(j)
+    assert rv.status_code == 402
+    assert j["status"]["app_code"] == 1402
+