customize the error return

[jinleileiking]

If the input type is error, gateway will return a json.

I need to customize the message. Is there a way ?

➜  ~ git:(master) ✗ curl 'localhost:9998/v1/example/echo?name=dddd'
{"error":"strconv.ParseInt: parsing \"dddd\": invalid syntax","code":3}%

the name is int32

[pieterlouw]

Have a look at this PR: #397

Is there a specific reason why you would want to customize the message? Will a HTTP 400 suffice?

[jinleileiking]

I am working at ksyun openapi, we need to let the return format be the same. So we need to customize.

https://docs.ksyun.com/read/latest/116/_book/KLSAPI/CancelRecordTask.html

[tamalsaha]

@jinleileiking , you might be out of luck. gRPC protocol defines its status using a Status proto. grpc/grpc-go#1156
https://github.com/grpc/grpc-go/blob/master/status/status.go

Gateway just turns that into a JSON object.

[tamalsaha]

@jinleileiking , I think you need to set the HTTPError for runtime.Servemux. See https://github.com/grpc-ecosystem/grpc-gateway/blob/master/runtime/mux.go#L98

[vaporz]

+1
I'm having the same issue.
@pieterlouw I was going to create a PR exactly the same with #397 , until I see this issue.

@tamalsaha Hi, our company is recently trying to build micro services using grpc-gateway, and I'm using HTTPError to handle errors. In this case, the error HTTPError receives is the error from "strconv.ParseInt()". I can not assert that, a ParseInt() error is an InvalidArgument error, and then return a HTTP 4xx. More detail is needed, HTTPError has to know what exactly is happening.

[vaporz]

Hi, I created a PR #409 , it's almost the same with #397 .
For we are blocked by this issue, if there is anything I can help with, please let me know.
Thank you!

[ewang]

A workaround I've used is to have server pass the error details via a trailer metadata, the on the grpc-gateway side, override the HTTPError handler to read from the trailer metadata.

This doesn't quite work for grpc-gateway side errors; for those I just special cased them in the HTTPError handler.

[jinleileiking]

I will test lately.

[jinleileiking]

The return message is:

{"error":"type mismatch, parameter: num, error: strconv.ParseInt: parsing \"aaa\": invalid syntax","code":3}

We should completely customize this return.( Use template?)

We should not change the core code. We need a config file ??? to set this line:

+		return nil, metadata, status.Errorf(codes.InvalidArgument, "type mismatch, parameter: %s, error: %v", {{$param | printf "%q"}}, err)

[jinleileiking]

@jinleileiking , I think you need to set the HTTPError for runtime.Servemux. See https://github.com/grpc-ecosystem/grpc-gateway/blob/master/runtime/mux.go#L98

It seems the way to solve this problem. I will dig into it.

[jinleileiking]

We should export handleForwardResponseServerMetadata

[c4milo]

I'm also looking forward to being able to return custom errors, or at the very least, serialize also status details I'm sending from the server.