Build gRPC Interceptors for Logging, Auth, and Rate Limiting - The Networker

                      TASK
                    

Implementation

Build a gRPC interceptor pipeline. Interceptors are middleware that wrap gRPC handler calls, running logic before and after the actual service method.

Interceptor chain: logging -> auth -> rate_limit -> handler

Implement handlers:

Request:  {"type": "grpc_call", "msg_id": 1, "service": "KeyValue", "method": "Get", "request": {"key": "k1"}, "metadata": {"authorization": "Bearer valid_token"}}
Response: {"type": "grpc_call_ok", "in_reply_to": 1, "status": "OK", "interceptors_applied": ["logging", "auth", "rate_limit"], "response": {"key": "k1", "value": "v1", "found": true}}

Request:  {"type": "grpc_call", "msg_id": 2, "service": "KeyValue", "method": "Get", "request": {"key": "k1"}, "metadata": {}}
Response: {"type": "grpc_call_ok", "in_reply_to": 2, "status": "UNAUTHENTICATED", "interceptor_failed": "auth"}

Request:  {"type": "grpc_interceptor_stats", "msg_id": 3}
Response: {"type": "grpc_interceptor_stats_ok", "in_reply_to": 3, "stats": {
    "total_requests": 2, "auth_failures": 1, "rate_limited": 0
}}

Sample Test Cases

Authenticated request passes all interceptorsTimeout: 5000ms

Input

{"src":"c0","dest":"n1","body":{"type":"init","msg_id":1,"node_id":"n1","node_ids":["n1"]}}
{"src":"c1","dest":"n1","body":{"type":"grpc_call","msg_id":2,"service":"KeyValue","method":"Put","request":{"key":"k1","value":"v1"},"metadata":{"authorization":"Bearer valid_token"}}}

Expected Output

{"src": "n1", "dest": "c0", "body": {"type": "init_ok", "in_reply_to": 1, "msg_id": 0}}

Missing auth token fails at auth interceptorTimeout: 5000ms

Input

{"src":"c0","dest":"n1","body":{"type":"init","msg_id":1,"node_id":"n1","node_ids":["n1"]}}
{"src":"c1","dest":"n1","body":{"type":"grpc_call","msg_id":2,"service":"KeyValue","method":"Get","request":{"key":"k1"},"metadata":{}}}

Expected Output

{"src": "n1", "dest": "c0", "body": {"type": "init_ok", "in_reply_to": 1, "msg_id": 0}}
{"src": "n1", "dest": "c1", "body": {"type": "grpc_call_ok", "in_reply_to": 2, "status": "UNAUTHENTICATED", "interceptor_failed": "auth", "msg_id": 1}}

Hints

Hint 1▾

Interceptors are middleware for gRPC calls, similar to HTTP middleware

Hint 2▾

They run before and after the actual handler

Hint 3▾

Chain multiple interceptors: logging -> auth -> rate_limit -> handler

Hint 4▾

Auth interceptor checks metadata for a valid token

Hint 5▾

Rate limiter uses a token bucket per client IP

Resources

gRPC Interceptors in Go

How to implement client and server interceptors for gRPC

                      OVERVIEW
                    

Theoretical Hub

Concept overview coming soon

Key Concepts

interceptormiddlewareauthenticationrate limitingrequest pipeline

main.py

python