Negroni

Negroni is an idiomatic approach to web middleware in Go. Learn how to set it up with Sentry.

For a quick reference, there is a complete example at the Go SDK source code repository.

Go Dev-style API documentation is also available.

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go get github.com/getsentry/sentry-go/negroni
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import (
	"fmt"
	"net/http"

	"github.com/getsentry/sentry-go"
	sentrynegroni "github.com/getsentry/sentry-go/negroni"
	"github.com/urfave/negroni"
)

// To initialize Sentry's handler, you need to initialize Sentry itself beforehand
if err := sentry.Init(sentry.ClientOptions{
	Dsn: "https://examplePublicKey@o0.ingest.sentry.io/0",
	EnableTracing: true,
	// Set TracesSampleRate to 1.0 to capture 100%
	// of transactions for performance monitoring.
	// We recommend adjusting this value in production,
	TracesSampleRate: 1.0,
}); err != nil {
	fmt.Printf("Sentry initialization failed: %v\n", err)
}

// Then create your app
app := negroni.Classic()

// Once it's done, you can attach the handler as one of your middleware
app.Use(sentrynegroni.New(sentrynegroni.Options{}))

// Set up routes
mux := http.NewServeMux()

mux.HandleFunc("/", func(rw http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "Hello world!")
})

app.UseHandler(mux)

// And run it
http.ListenAndServe(":3000", app)

sentrynegroni accepts a struct of Options that allows you to configure how the handler will behave.

Currently it respects 3 options:

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// Whether Sentry should repanic after recovery, in most cases it should be set to true,
// as negroni.Classic includes its own Recovery middleware that handles http responses.
Repanic bool
// Whether you want to block the request before moving forward with the response.
// Because Negroni's default `Recovery` handler doesn't restart the application,
// it's safe to either skip this option or set it to `false`.
WaitForDelivery bool
// Timeout for the event delivery requests.
Timeout time.Duration

sentrynegroni attaches an instance of *sentry.Hub (https://pkg.go.dev/github.com/getsentry/sentry-go#Hub) to the request's context, which makes it available throughout the rest of the request's lifetime. You can access it by using the sentry.GetHubFromContext() method on the request itself in any of your proceeding middleware and routes. And it should be used instead of the global sentry.CaptureMessage, sentry.CaptureException, or any other calls, as it keeps the separation of data between the requests.

Keep in mind that *sentry.Hub won't be available in middleware attached before sentrynegroni!

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app := negroni.Classic()

app.Use(sentrynegroni.New(sentrynegroni.Options{
	Repanic: true,
}))

app.Use(negroni.HandlerFunc(func(rw http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
	hub := sentry.GetHubFromContext(r.Context())
	hub.Scope().SetTag("someRandomTag", "maybeYouNeedIt")
	next(rw, r)
}))

mux := http.NewServeMux()

mux.HandleFunc("/", func(rw http.ResponseWriter, r *http.Request) {
	hub := sentry.GetHubFromContext(r.Context())
	hub.WithScope(func(scope *sentry.Scope) {
		scope.SetExtra("unwantedQuery", "someQueryDataMaybe")
		hub.CaptureMessage("User provided unwanted query string, but we recovered just fine")
	})
	rw.WriteHeader(http.StatusOK)
})

mux.HandleFunc("/foo", func(rw http.ResponseWriter, r *http.Request) {
	// sentrynagroni handler will catch it just fine. Also, because we attached "someRandomTag"
	// in the middleware before, it will be sent through as well
	panic("y tho")
})

app.UseHandler(mux)

http.ListenAndServe(":3000", app)

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sentry.Init(sentry.ClientOptions{
	Dsn: "https://examplePublicKey@o0.ingest.sentry.io/0",
	BeforeSend: func(event *sentry.Event, hint *sentry.EventHint) *sentry.Event {
		if hint.Context != nil {
			if req, ok := hint.Context.Value(sentry.RequestContextKey).(*http.Request); ok {
				// You have access to the original Request here
			}
		}

		return event
	},
})

Negroni provides an option called PanicHandlerFunc, which lets you "plug-in" to its default Recovery middleware.

sentrynegroni exports a very barebones implementation, which utilizes it, so if you don't need anything else than just reporting panics to Sentry, you can use it instead, as it's just one line of code!

You can still use BeforeSend and event processors to modify data before delivering it to Sentry, using this method as well.

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app := negroni.New()

recovery := negroni.NewRecovery()
recovery.PanicHandlerFunc = sentrynegroni.PanicHandlerFunc

app.Use(recovery)

mux := http.NewServeMux()
mux.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
	panic("y tho")
})

app.UseHandler(mux)

http.ListenAndServe(":3000", app)
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