spring-cloud-gateway-grpc-status-bug

This repository is an example that describes a bug in spring-cloud-gateway when using grpc and a service returns grpc errors. Whenever gRPC responses return a status that is results in an error (grpc-status != 0) then gateway does not reply properly.

Project structure

This project contains three main modules:

• Root: spring-cloud-gateway
• grpc-server
• grpc-client

spring-cloud-gateway

This is an implementation of gateway to reproduce the buggy behaviour. The gateway is configured to route traffic for GRPC requests based on the header to localhost:8082

gRPC server

Simple gRPC server that servers one endpoint to pong a request

gRPC client

Simple gRPC client with two configs:

• direct this profile will directly do calls to the gRPC server
• gateway this profile will call the gRPC server via the gateway.

The client has two command line runners

• One that runs an OK request, this will result in an OK "Pong" response from the gRPC service.
• One that runs a request which will result in an error being returned by the server

How to reproduce the bug

1. Build the project ./gradlew clean build

2. Start the gateway and the grpc server ./gradlew :bootRun ./gradlew :grpc-server:bootRun

3. Run the client with direct OK profile to validate grpc server running: ./gradlew :grpc-client:bootRunDirectOk. You should see a log with message: "Pong"

4. Run the client with direct Error profile to validate grpc server running and returning an error result: ./gradlew :grpc-client:bootRunDirectError. The runner should throw an exception with root cause io.grpc.StatusRuntimeException: INTERNAL

5. Run the client with gateway OK to display correct behaviour ./gradlew :grpc-client:bootRunGatewayOk. You should see a log with message: "Pong"

6. Run the client with gateway Error to display the buggy behaviour ./gradlew :grpc-client:bootRunGatewayError. The runner will hang because gateway returns a "grpc-status" with value "0" while it should've returned the correct status.

How to reproduce potential fix

1. Build the project ./gradlew clean build

2. Start the gateway and the grpc server ./gradlew :bootRun ./gradlew :grpc-server:bootRunWithPatchedFilter This will run the gateway with a patched filter that properly returns the "grpc-status" as a trailing header.

3. Run the client with direct OK profile to validate grpc server running: ./gradlew :grpc-client:bootRunDirectOk. You should see a log with message: "Pong"

4. Run the client with direct Error profile to validate grpc server running and returning an error result: ./gradlew :grpc-client:bootRunDirectError. The runner should throw an exception

5. Run the client with gateway OK to display correct behaviour ./gradlew :grpc-client:bootRunGatewayOk. You should see a log with message: "Pong"

6. Run the client with gateway Error to display the buggy behaviour ./gradlew :grpc-client:bootRunGatewayError. the runner will return a correct value

The fix here is a PatchedGRPCResponseHeaderFilter that is run after the default GRPCResponseHeadersFilter which returns the grpc-stats properly.

Bug Explanation

The current GRPCResponseHeadersFilter always returns the grpc-status trailing header with a value "0". This is an OK result according to the gRPC protocol see: grpc-status-codes

The GRPCResponseHeadersFilter should return a proper grpc-status which is copied from the request to properly handle requests that result in an error.