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https://github.com/maruel/panicparse

Crash your app in style (Golang)
https://github.com/maruel/panicparse

crash go panic stack-traces

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Crash your app in style (Golang)

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# panicparse



Parses panic stack traces, densifies and deduplicates goroutines with similar

stack traces. Helps debugging crashes and deadlocks in heavily parallelized

process.



[![PkgGoDev](https://pkg.go.dev/badge/github.com/maruel/panicparse/v2/stack)](https://pkg.go.dev/github.com/maruel/panicparse/v2/stack)

[![codecov](https://codecov.io/gh/maruel/panicparse/branch/main/graph/badge.svg?token=izj1cLjUi3)](https://codecov.io/gh/maruel/panicparse)

[![go-recipes](https://raw.githubusercontent.com/nikolaydubina/go-recipes/main/badge.svg?raw=true)](https://github.com/nikolaydubina/go-recipes#-pretty-print-panic-messages)



panicparse helps make sense of Go crash dumps:



![Screencast](https://raw.githubusercontent.com/wiki/maruel/panicparse/parse.gif "Screencast")



## Features



   * Race detector support, e.g. it can parse output produced by `go test -race`

   * HTML export.

   * Easy to use as an [HTTP Handler

     middleware](https://pkg.go.dev/github.com/maruel/panicparse/v2/stack#example-package-HttpHandlerMiddleware).

   * High performance parsing.

   * [HTTP web server](https://pkg.go.dev/github.com/maruel/panicparse/v2/stack/webstack#SnapshotHandler)

     that serves a very tight and swell snapshot of your goroutines, much more

     readable than [net/http/pprof](https://pkg.go.dev/net/http/pprof).

   * >50% more compact output than original stack dump yet more readable.

   * Deduplicates redundant goroutine stacks. Useful for large server crashes.

   * Arguments as pointer IDs instead of raw pointer values.

   * Pushes stdlib-only stacks at the bottom to help focus on important code.

   * Parses the source files if available to augment the output.

   * Works on any platform supported by Go, including Windows, macOS, linux.

   * Full go module support.

   * Requires >=go1.17. Use v2.3.1 for older Go versions.



## Installation



    go install github.com/maruel/panicparse/v2/cmd/pp@latest



## Usage



### Piping a stack trace from another process



#### TL;DR



   * Ubuntu (bash v4 or zsh): `|&`

   * macOS, [install bash 4+](README.md#updating-bash-on-macos), then: `|&`

   * Windows _or_ macOS with stock bash v3: `2>&1 |`

   * [Fish](http://fishshell.com/) shell: `&|`



#### Longer version



`pp` streams its stdin to stdout as long as it doesn't detect any panic.

`panic()` and Go's native deadlock detector [print to

stderr](https://golang.org/src/runtime/panic1.go) via the native [`print()`

function](https://golang.org/pkg/builtin/#print).



**Bash v4** or **zsh**: `|&` tells the shell to redirect stderr to stdout,

it's an alias for `2>&1 |` ([bash

v4](https://www.gnu.org/software/bash/manual/bash.html#Pipelines),

[zsh](http://zsh.sourceforge.net/Doc/Release/Shell-Grammar.html#Simple-Commands-_0026-Pipelines)):



    go test -v |&pp



**Windows or macOS native bash** [(which is

3.2.57)](http://meta.ath0.com/2012/02/05/apples-great-gpl-purge/): They don't

have this shortcut, so use the long form:



    go test -v 2>&1 | pp



**Fish**: `&|` redirects stderr and stdout. It's an alias for `2>&1 |`

([fish piping](https://fishshell.com/docs/current/language.html#piping)):



    go test -v &| pp



**PowerShell**: [It has broken `2>&1` redirection](https://connect.microsoft.com/PowerShell/feedback/details/765551/in-powershell-v3-you-cant-redirect-stderr-to-stdout-without-generating-error-records). The workaround is to shell out to cmd.exe. :(



### Investigate deadlock



On POSIX, use `Ctrl-\` to send SIGQUIT to your process, `pp` will ignore

the signal and will parse the stack trace.



### Parsing from a file



To dump to a file then parse, pass the file path of a stack trace



    go test 2> stack.txt

    pp stack.txt



## Tips



### Disable inlining



The Go toolchain inlines functions when it can. This causes traces to be less

informative. Optimization also interfere with traces. You can use the following

to help diagnosing issues:



    go install -gcflags '-N -l' path/to/foo

    foo |& pp



or



    go test -gcflags '-N -l' ./... |& pp



Run `go tool compile -help` to get the full list of valid values for -gcflags.



### GOTRACEBACK



By default, [`GOTRACEBACK`](https://golang.org/pkg/runtime/) defaults to

`single`, which means that a panic will only return the current goroutine trace

alone. To get all goroutines trace and not just the crashing one, set the

environment variable:



    export GOTRACEBACK=all



or `set GOTRACEBACK=all` on Windows. Probably worth to put it in your `.bashrc`.



### Updating bash on macOS



Install bash v4+ on macOS via [homebrew](http://brew.sh) or

[macports](https://www.macports.org/). Your future self will appreciate having

done that.



### If you have `/usr/bin/pp` installed



If you try `pp` for the first time and you get:



    Creating tables and indexes...

    Done.



and/or



    /usr/bin/pp5.18: No input files specified



you may be running the _Perl PAR Packager_ instead of panicparse.



You have two choices, either you put `$GOPATH/bin` at the beginning of `$PATH`

or use long name `panicparse` with:



    go install github.com/maruel/panicparse/v2@latest



then using `panicparse` instead of `pp`:



    go test 2> panicparse



Hint: You may also use shell aliases



    alias gp=panicparse

    go test 2> gp



    alias p=panicparse

    go test 2> p



### webstack in action



The

[webstack.SnapshotHandler](https://pkg.go.dev/github.com/maruel/panicparse/v2/stack/webstack#SnapshotHandler)

http.Handler enables glancing at at a snapshot of your process trivially:



![Screencast](https://raw.githubusercontent.com/wiki/maruel/panicparse/panicparse_webstack.gif "Screencast")



## Authors



`panicparse` was created with ❤️️ and passion by [Marc-Antoine

Ruel](https://github.com/maruel) and

[friends](https://github.com/maruel/panicparse/graphs/contributors).