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danielgtaylor / huma

Huma REST/HTTP API Framework for Golang with OpenAPI 3.1
https://huma.rocks/
MIT License
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[question] about panic with `error marshaling response: ... context canceled`. #632

Open superstas opened 1 week ago

superstas commented 1 week ago

Hi there,

I have a question about the panic that happens here.

We've been facing such panic in our logs for some time, and the err is context canceled.

We use humaecho adapter that uses echo.Context.Response under the hood.

Sometimes, we get context canceled err on api.Marshal(ctx.BodyWriter(), ct, tval), which forces Huma to panic.

How to reproduce? I took `humamux` adapter and added `mockBodyWriter` that returns `context.Canceled` **mock_adapter.go** ```go package main import ( "context" "crypto/tls" "io" "mime/multipart" "net/http" "net/url" "time" "github.com/danielgtaylor/huma/v2" "github.com/danielgtaylor/huma/v2/queryparam" "github.com/gorilla/mux" ) // mockBodyWriter is a mock implementation of io.Writer that returns context.Canceled error. type mockBodyWriter struct{} func (w mockBodyWriter) Write(p []byte) (n int, err error) { return 0, context.Canceled } // MultipartMaxMemory is the maximum memory to use when parsing multipart // form data. var MultipartMaxMemory int64 = 8 * 1024 type gmuxContext struct { op *huma.Operation r *http.Request w http.ResponseWriter status int } // check that gmuxContext implements huma.Context var _ huma.Context = &gmuxContext{} func (c *gmuxContext) Operation() *huma.Operation { return c.op } func (c *gmuxContext) Context() context.Context { return c.r.Context() } func (c *gmuxContext) Method() string { return c.r.Method } func (c *gmuxContext) Host() string { return c.r.Host } func (c *gmuxContext) RemoteAddr() string { return c.r.RemoteAddr } func (c *gmuxContext) URL() url.URL { return *c.r.URL } func (c *gmuxContext) Param(name string) string { return mux.Vars(c.r)[name] } func (c *gmuxContext) Query(name string) string { return queryparam.Get(c.r.URL.RawQuery, name) } func (c *gmuxContext) Header(name string) string { return c.r.Header.Get(name) } func (c *gmuxContext) TLS() *tls.ConnectionState { return c.r.TLS } func (c *gmuxContext) Version() huma.ProtoVersion { return huma.ProtoVersion{ Proto: c.r.Proto, ProtoMajor: c.r.ProtoMajor, ProtoMinor: c.r.ProtoMinor, } } func (c *gmuxContext) EachHeader(cb func(name, value string)) { for name, values := range c.r.Header { for _, value := range values { cb(name, value) } } } func (c *gmuxContext) BodyReader() io.Reader { return c.r.Body } func (c *gmuxContext) GetMultipartForm() (*multipart.Form, error) { err := c.r.ParseMultipartForm(MultipartMaxMemory) return c.r.MultipartForm, err } func (c *gmuxContext) SetReadDeadline(deadline time.Time) error { return huma.SetReadDeadline(c.w, deadline) } func (c *gmuxContext) SetStatus(code int) { c.status = code c.w.WriteHeader(code) } func (c *gmuxContext) Status() int { return c.status } func (c *gmuxContext) AppendHeader(name string, value string) { c.w.Header().Add(name, value) } func (c *gmuxContext) SetHeader(name string, value string) { c.w.Header().Set(name, value) } func (c *gmuxContext) BodyWriter() io.Writer { return mockBodyWriter{} } type gMux struct { router *mux.Router } func (a *gMux) Handle(op *huma.Operation, handler func(huma.Context)) { a.router. NewRoute(). Path(op.Path). Methods(op.Method). HandlerFunc(func(w http.ResponseWriter, r *http.Request) { handler(&gmuxContext{op: op, r: r, w: w}) }) } func (a *gMux) ServeHTTP(w http.ResponseWriter, r *http.Request) { a.router.ServeHTTP(w, r) } func New(r *mux.Router, config huma.Config) huma.API { return huma.NewAPI(config, &gMux{router: r}) } ``` **main.go** ```go package main import ( "context" "net/http" "github.com/danielgtaylor/huma/v2" "github.com/gorilla/mux" ) type ( User struct { Name string `json:"name" minLength:"1" maxLength:"32"` Surname string `json:"surname" minLength:"1" maxLength:"32"` } CreateUserInput struct { Body User } CreateUserOutput struct { Body struct { Message string `json:"message"` } } ) func addRoutes(api huma.API) { huma.Register(api, huma.Operation{ OperationID: "CreateUser", Method: http.MethodPost, Path: "/user", }, func(ctx context.Context, input *CreateUserInput) (*CreateUserOutput, error) { resp := &CreateUserOutput{} resp.Body.Message = "CreateUser works!" return resp, nil }) } func main() { router := mux.NewRouter() api := New(router, huma.DefaultConfig("My API", "1.0.0")) addRoutes(api) http.ListenAndServe("127.0.0.1:8888", router) } ``` **cURL request** ```sh $> curl -v http://127.0.0.1:8888/user -H "Content-Type: application/json" -d '{"name": "Foo", "surname": "Bar"}' * Trying 127.0.0.1:8888... * Connected to 127.0.0.1 (127.0.0.1) port 8888 (#0) > POST /user HTTP/1.1 > Host: 127.0.0.1:8888 > User-Agent: curl/7.81.0 > Accept: */* > Content-Type: application/json > Content-Length: 33 > * Empty reply from server * Closing connection 0 curl: (52) Empty reply from server ``` **Server output** ```sh 2024/10/31 13:44:52 http: panic serving 127.0.0.1:35094: error marshaling response for POST /user 200: context canceled goroutine 20 [running]: net/http.(*conn).serve.func1() /home/superstas/.gvm/gos/go1.23.2/src/net/http/server.go:1947 +0xbe panic({0x719be0?, 0xc000140c00?}) /home/superstas/.gvm/gos/go1.23.2/src/runtime/panic.go:785 +0x132 github.com/danielgtaylor/huma/v2.transformAndWrite({0x7fd0f8, 0xc0001880e0}, {0x7fe3b8, 0xc0001d6d20}, 0xc8, {0x76dc86, 0x10}, {0x71c9e0, 0xc00011fd80}) /home/superstas/.gvm/pkgsets/go1.23.2/global/pkg/mod/github.com/danielgtaylor/huma/v2@v2.24.0/huma.go:480 +0x313 github.com/danielgtaylor/huma/v2.Register[...].func1() /home/superstas/.gvm/pkgsets/go1.23.2/global/pkg/mod/github.com/danielgtaylor/huma/v2@v2.24.0/huma.go:1465 +0x105c main.(*gMux).Handle.func1({0x7fb1e0, 0xc000188380}, 0xc0001fe280) /home/superstas/projects/humatest/adapter_mock.go:138 +0xa2 net/http.HandlerFunc.ServeHTTP(0xc0001fe140?, {0x7fb1e0?, 0xc000188380?}, 0x10?) /home/superstas/.gvm/gos/go1.23.2/src/net/http/server.go:2220 +0x29 github.com/gorilla/mux.(*Router).ServeHTTP(0xc0001c60c0, {0x7fb1e0, 0xc000188380}, 0xc0001fe000) /home/superstas/.gvm/pkgsets/go1.23.2/global/pkg/mod/github.com/gorilla/mux@v1.8.1/mux.go:212 +0x1e2 net/http.serverHandler.ServeHTTP({0x7f9f28?}, {0x7fb1e0?, 0xc000188380?}, 0x6?) /home/superstas/.gvm/gos/go1.23.2/src/net/http/server.go:3210 +0x8e net/http.(*conn).serve(0xc0001902d0, {0x7fb648, 0xc0001d6a50}) /home/superstas/.gvm/gos/go1.23.2/src/net/http/server.go:2092 +0x5d0 created by net/http.(*Server).Serve in goroutine 1 /home/superstas/.gvm/gos/go1.23.2/src/net/http/server.go:3360 +0x485 ```

Questions

Overall, I want to understand the reasons behind this logic before doing anything else.

Thank you.

danielgtaylor commented 5 days ago

@superstas thanks for the question. The client disconnecting is indeed a valid use case. We have seen these messages too and tend to ignore them, but it's probably better to filter these panics out in Huma now that I'm thinking about it. We could check if marshaling fails and if the context is canceled we just stop. Something like this:

if ctx.Context().Err() == context.Canceled {
    // The client disconnected, so don't bother writing anything.
    return
}
superstas commented 5 days ago

@danielgtaylor thank you for the reply.

Yes, checking the root cause of the marshaling failure and filtering out disconnected client cases sounds logical to me as well.