# Use GRPC Server Interceptor

**URL:** <https://discourse.nameko.io/t/use-grpc-server-interceptor/466>\
**Category:** Uncategorized\
**Created:** [June 26, 2019, 9:46pm UTC](https://discourse.nameko.io/t/use-grpc-server-interceptor/466 "2019-06-26T21:46:17Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![ArjunBansil](https://avatars.discourse-cdn.com/v4/letter/a/f6c823/32.png) [@ArjunBansil](https://discourse.nameko.io/u/ArjunBansil)\
**Post date:** [June 26, 2019, 9:46pm UTC](https://discourse.nameko.io/t/use-grpc-server-interceptor/466/1 "2019-06-26T21:46:17Z")

</div>

I need to use a gRPC server interceptor to get some metrics. I’m extending grpc.ServerInterceptor if that helps. Using basic gRPC server examples, it’s very straightforward, but how I would implement this using nameko?

My server code

```
import socket
import time
import traceback

from nameko.rpc import rpc
from nameko_grpc.entrypoint import Grpc

from pred_pb2 import PredictReply
from pred_pb2_grpc import PredictorStub
from word_predictor import RwGenerator

# Docker Command for running local rabbitmq instance
# docker run -p 5672:5672 --hostname nameko-rabbitmq rabbitmq:3
# implements the predictor stub and allows you to use gRPC endpoints
grpc = Grpc.implementing(PredictorStub)

class PredictorService:
    # Declaration of the Predictor Service

    name = "Predictor" # Name of the service
    predictor = None # the random word predictor model

    @staticmethod
    def is_iterable(a):
        try:
            iter(a)
        except TypeError:
            return False
        else:
            return True

    # Initializes the predictor service
    # Loads the corpus text file
    # Does the data preparation in the init so that there's less lag when sending predictions
    def __init__ (self):
        path = "corpus.txt"
        s = open(path, encoding="ascii", errors="surrogateescape").read().lower()
        self.predictor = RwGenerator(s)
        self.predictor.prepare_data(None)

    # Sends five random words back in PredictReply
    @grpc
    def make_prediction(self, request, context):
        if self.is_iterable(request):
            context.set_code(grpc.StatusCode.INVALID_ARGUMENT)
            context.set_details("Sent a stream, was expecting a unary request")
            return PredictReply()
        print("Unary-Unary Prediction")
        words = self.predictor.predict_completions(None, 5)

        return PredictReply(word1=words[0], word2=words[1], word3=words[2], word4=words[3], word5=words[4])

    # Sends five random words in stream format
    @grpc
    def unary_stream_prediction(self, request, context):
        if self.is_iterable(request):
            context.set_code(grpc.StatusCode.INVALID_ARGUMENT)
            context.set_details("Sent a stream, was expecting a unary request")
            return PredictReply()
        print("Unary-Stream Prediction")
        words = self.predictor.predict_completions(None, 5)

        for word in words:
            yield PredictReply(word1=word)

    # Gets a stream of inputs and sends 5 words back in a single request
    @grpc
    def stream_unary_prediction(self, request_iterator, context):
        print("Stream-Unary Prediction")
        words = self.predictor.predict_completions(None, 5)
        return PredictReply(word1=words[0], word2=words[1], word3=words[2], word4=words[3], word5=words[4])

    # Gets a stream of inputs and sends 8 words in a stream
    @grpc
    def stream_stream_prediction(self, request_iterator, context):
        print("Stream-Stream Prediction")
        words = self.predictor.predict_completions(None, 5)
        for word in words:
            print(word)
            yield PredictReply(word1=word)

    # Method for checking if server is up and running and can be easily executed from nameko shell
    @rpc
    def hello(self, name):
        return "hello, " + socket.gethostbyname(socket.gethostname()) + " {}!".format(name)
    `indent preformatted text by 4 spaces`
```

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<div class="post-metadata">

**Author:** ![mattbennett](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.nameko.io/mattbennett/32/13_2.png) [@mattbennett](https://discourse.nameko.io/u/mattbennett)\
**Post date:** [June 27, 2019, 1:24pm UTC](https://discourse.nameko.io/t/use-grpc-server-interceptor/466/2 "2019-06-27T13:24:43Z")

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Hi @ArjunBansil,

I’m not sure I understand your question. What is the `grpc.ServerInterceptor` code are you extending? Is your desire to implement the server interceptor in Nameko, or put the server interceptor in front of your Nameko service?

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<div class="post-metadata">

**Author:** ![ArjunBansil](https://avatars.discourse-cdn.com/v4/letter/a/f6c823/32.png) [@ArjunBansil](https://discourse.nameko.io/u/ArjunBansil)\
**Post date:** [June 28, 2019, 1:47pm UTC](https://discourse.nameko.io/t/use-grpc-server-interceptor/466/3 "2019-06-28T13:47:49Z")

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I’m sorry this is all very new to me. In normal grpc examples using futures package to create a server, you can use the following code block to add an interceptor.

```
server = grpc.server(futures.ThreadPoolExecutor(max_workers=10), interceptors=(interceptor(), ))

```

So I have code that extends grpc.ServerInterceptor that works using grpc.server. How would I implement this similar functionality using Nameko? Hopefully this clears things up.

@mattbennett

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<div class="post-metadata">

**Author:** ![mattbennett](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.nameko.io/mattbennett/32/13_2.png) [@mattbennett](https://discourse.nameko.io/u/mattbennett)\
**Post date:** [June 29, 2019, 8:37pm UTC](https://discourse.nameko.io/t/use-grpc-server-interceptor/466/4 "2019-06-29T20:37:13Z")

</div>

OK thanks, I understand. Unfortunately nameko-grpc doesn’t have support for interceptors yet, but wouldn’t be too tricky to add it.

To accept a server interceptor, the `GrpcServer` class in `nameko_grpc.entrypoint` would need to start accepting interceptors (in the same way that `grpc.Server` does) and then instead of this:

> <https://github.com/nameko/nameko-grpc/blob/32a9144799da7fe89e7d52178829f4bcd9b485b7/nameko_grpc/entrypoint.py#L139-L141>

… we’d do something similar to `grpc.Server`:

> <https://github.com/grpc/grpc/blob/b6514a64386eefe093b712a1a51b915cbe18359d/src/python/grpcio/grpc/_server.py#L679-L683>