debugger

README

Debugger Middleware

This package provides a debugging middleware for Go applications to enable better display of goroutines in the debugger.

It has nearly-zero performance penalty in production code when not actively used.

How this looks like in the IDE

Below you can see how this feature looks like in GoLand IDE:

How to use

Include it in your application using one of the patterns below.

Then, compile the application with -tags debugger, e.g.

go build -tags debugger

More details on how to use this can be found in this blog post: https://blog.jetbrains.com/go/2020/03/03/how-to-find-goroutines-during-debugging/

HTTP handlers

In your code, replace the HTTP handler with the Middleware function call.

Original:

router.HandleFunc("/", homeHandler)

Replacement:

router.HandleFunc("/", debugger.Middleware(homeHandler, func(r *http.Request) []string {
    return []string{
        "path", r.RequestURI,
    }
}))

Non-HTTP handlers

For normal functions/methods, you can use the SetLabels / SetLabelsCtx functions to set the debugger labels.

Original:

func sum(a, b int) int {
    return a+b
}

Replacement:

func sum(a, b int) int {
    debugger.SetLabels(func() []string {
        return []string{
            "a", strconv.Itoa(a),
            "b", strconv.Itoa(b),
        }
    })

    return a+b
}

Performance

You can asses the performance of this library by running the included benchmarks in your environment.

Here are the results from my own machine (Intel Core i7 6700HQ, 32GB RAM, Windows 10), when running with a -count=5 pass, averaged across runs.

Go 1.13.8

Without labels:

Name	go 1.13.8		go 1.14 RC1
	Execution count	Time	Execution count	Time
BenchmarkWorkerWithout-8	3255558	370 ns/op	3183910	368 ns/op
BenchmarkWorkerWithOne-8	25938	45698 ns/op	25643	46479 ns/op
BenchmarkWorkerWithThree-8	15656	78222 ns/op	19754	60131 ns/op
BenchmarkWorkerWithTen-8	5776	216798 ns/op	7322	171842 ns/op
BenchmarkWorkerWithConv-8	15374	79609 ns/op	19049	63818 ns/op

License

This project is provided under the MIT license.

Documentation

Overview

Debugger package allows an application to be compiled for production without incurring any penalty due to instrumentation.

When the time comes to use a debugger and inspect your code, use the -tags=debugger build tag to switch the implementation to one that will set labels that can be displayed in the debugger.

The current implementation relies on pprof labels to be created and then the debugger can read them and display them.

Index

• func Middleware(f http.HandlerFunc, l MiddlewareLabels) http.HandlerFunc
• func SetLabels(l Labels)
• type Labels
• type MiddlewareLabels

Functions

func Middleware

func Middleware(f http.HandlerFunc, l MiddlewareLabels) http.HandlerFunc

Middleware allows HTTP middleware to receive debugger labels

func SetLabels

func SetLabels(l Labels)

SetLabels will set debugger labels for any function/method call

Types

type Labels

type Labels func() []string

Labels generates the labels for a function/method

type MiddlewareLabels

type MiddlewareLabels func(r *http.Request) []string

MiddlewareLabels generates labels that are aware of the request properties