panicparse

README

panicparse

Parses panic stack traces, densifies and deduplicates goroutines with similar stack traces. Helps debugging crashes and deadlocks in heavily parallelized process.

panicparse helps make sense of Go crash dumps:

Features

• New in v1.4.0!: webstack.SnapshotHandler is a http handler that serves a very tight and swell snapshot of your goroutines, much more readable than net/http/pprof.
• >50% more compact output than original stack dump yet more readable.
• Exported symbols are bold, private symbols are darker.
• Stdlib is green, main is yellow, rest is red.
• 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 Windows.

webstack in action

Authors

panicparse was created with ❤️️ and passion by Marc-Antoine Ruel and friends.

Installation

go get github.com/maruel/panicparse/cmd/pp

Usage

Piping a stack trace from another process

TL;DR

• Ubuntu (bash v4 or zsh): |&
• macOS, install bash 4+, then: |&
• Windows or macOS with stock bash v3: 2>&1 |
• Fish 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 via the native print() function.

Bash v4 or zsh: |& tells the shell to redirect stderr to stdout, it's an alias for 2>&1 | (bash v4, zsh):

go test -v |&pp

Windows or macOS native bash (which is 3.2.57): They don't have this shortcut, so use the long form:

go test -v 2>&1 | pp

Fish: It uses ^ for stderr redirection so the shortcut is ^|:

go test -v ^|pp

PowerShell: It has broken 2>&1 redirection. 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

Starting with go1.11, the toolchain starts to inline more often. This causes traces to be less informative. You can use the following to help diagnosing issues:

go install -gcflags '-l' path/to/foo
foo |& pp

or

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

GOTRACEBACK

Starting with Go 1.6, GOTRACEBACK defaults to single instead of all / 1 that was used in 1.5 and before. 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 or macports. 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 get github.com/maruel/panicparse

then using panicparse instead of pp:

go test 2> panicparse

Documentation

Overview

panicparse: analyzes stack dump of Go processes and simplifies it.

It is mostly useful on servers will large number of identical goroutines, making the crash dump harder to read than strictly necessary.