Here is something I did to pass custom error information:
Based on the grpc code, if an error type has GRPCStatus()
*status.Status function, then grpc gets the status information using
that method. For the error types that can go through grpc, I have this
method below:
func (e MyError) GRPCStatus() *status.Status {
var code codes.Code
switch e.HTTPStatus {
case http.StatusBadRequest:
code = codes.InvalidArgument
case http.StatusUnauthorized:
code = codes.Unauthenticated
default:
code = codes.Unknown
}
x, _ := json.Marshal(e)
return status.New(code, string(x))
}
In this example, the error type includes an HTTP status code, and the
grpc status is decided based on that. The grpc error contains a JSON
marshaled error information.
On the receiving end, I have this function:
func FromGRPCError(err error) (MyError, bool) {
if x, ok := status.FromError(err); ok {
var e MyError
if json.Unmarshal([]byte(x.Message()), &e) == nil {
return e, true
}
}
return MyError{}, false
}
This decodes the error information from the incoming error.
This scheme can be extended to deal with multiple error types.
On Tue, May 18, 2021 at 8:45 AM 'Axel Wagner' via golang-nuts
<[email protected]> wrote:
>
> You cant to use status.Code(err), which gives you the gRPC status code.
>
>
> On Tue, May 18, 2021 at 3:08 PM [email protected] <[email protected]> wrote:
>>
>>
>> Thank you for the pointer. After looking at the API, I'm still confused how
>> to use it. I can status.Convert(err) to get a status object but couldn't
>> really figure how how to use that to extract the actual underlying base
>> error?
>> On Saturday, May 15, 2021 at 2:12:28 PM UTC+2 kortschak wrote:
>>>
>>> On Sat, 2021-05-15 at 04:47 -0700, [email protected] wrote:
>>> > In my local code, I'm using things like
>>> >
>>> > if errors.Is(err, api.ErrMustRetry) { ... }
>>> >
>>> > How would I achieve the same on errors returned by the gRCP
>>> > interface? I've noticed these are wrapped:
>>> >
>>> > rpc error: code = Unknown desc = must retry rpc error: code = Unknown
>>> > desc = must retry
>>> >
>>> > I assume the errors package won't work here as type information is
>>> > not carried across gRPC: What is the best practice here: unwrap the
>>> > root error from the RPC result (how) and perform string comparison?
>>> >
>>>
>>> There is the status package which provides tools for examining the gRPC
>>> errors, https://pkg.go.dev/google.golang.org/grpc/status.
>>>
>>>
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