2020-12-19 Update: I used to recommend to use github.com/maruel/panicparse/v2/cmd/pp path but it’s not required anymore. To upgrade run:
go get -u github.com/maruel/panicparse/cmd/pp
Never used it? See usage.
panicparse is a popular tool to condense and distill Go goroutine snapshots. v1.4.0 was great (see blog post) but there were a few big feature requests that I knew would require significant refactoring to support:
I’ve taken the last week to finish the implementation and polish these features. I’m glad to announce that panicparse v2.0.1 is now available for general use!
The race detector output is not generated by the Go standard library but instead by the LLVM thread sanitizer (TSan). This is why the output is so different. As such, I had to significantly improve the parsing state machine to be able to process this format.
Try it at home by compiling the racy version of the testing tool panic:
go get github.com/maruel/panicparse/v2/cmd/pp go get -race github.com/maruel/panicparse/v2/cmd/panic
The output of
panic race will look like this:
$ panic race GOTRACEBACK=all ================== WARNING: DATA RACE Read at 0x00c0001bc030 by goroutine 8: main.panicDoRaceRead() /firstname.lastname@example.org/cmd/panic/main.go:144 +0x3a main.panicRace.func2() /email@example.com/cmd/panic/main.go:161 +0x38 Previous write at 0x00c0001bc030 by goroutine 7: main.panicDoRaceWrite() /firstname.lastname@example.org/cmd/panic/main.go:139 +0x44 main.panicRace.func1() /email@example.com/cmd/panic/main.go:158 +0x38 Goroutine 8 (running) created at: main.panicRace() /firstname.lastname@example.org/cmd/panic/main.go:160 +0xa6 main.main() /email@example.com/cmd/panic/main.go:72 +0x712 Goroutine 7 (running) created at: main.panicRace() /firstname.lastname@example.org/cmd/panic/main.go:157 +0x84 main.main() /email@example.com/cmd/panic/main.go:72 +0x712 ==================
This is a bit hard to read. Thankfully, with the new race detector parsing
algorithm, the output becomes much more manageable with:
panic race |& pp
Another frequently requested feature is to officially support HTML output. While
panicparse had the
-html flag for a while, I never exposed it in the stack
package. This is now available for general use! Try it locally:
panic race |& pp -html a.html go get github.com/maruel/serve-dir serve-dir
then visit http://localhost:8010/a.html. It will look like this:
Go module detection was tricky to implement. Since the primary use case is for
local use, that’s what I optimized for with the initial release. The
implementation supports the use of the replace
Each detected source file is matched to one of these categories:
With this new detection logic, the previous color coding of “yellow, red, green”
had to be updated. A new color coded legend was created, as you can see in the
HTML screenshot above. The
pp tool also use new colors and the legend is
The stack.ParseDump() function was replaced with stack.ScanSnapshot(). It now stops fetching the input after it is done processing a goroutines snapshot, so it is now possible to process consecutive snapshots.
→ This enables extracting the crashes from a server log and do analytics on it!
There’s a ton of other improvements. I’ve improved
tweaked the parsing to be more solid and improved performance. It now supports
arbitrarily long lines while being memory efficient in the common case. I
increased test coverage.
#TFW you spend 2 hours to write >100 lines of new unit test code to test corner cases, and the code coverage increases only by 0.3%.— Marc-Antoine Ruel (@marcaruel) August 5, 2020
I revived the Go source parsing algorithm to enhance the arguments presentation, and updated the unit tests accordingly to ensure it doesn’t break again, then made it the default. The project is now tested on 1.9.7, 1.12.7 and the current version, and tested on MacOS, Ubuntu and Windows. Previously I was manually copying the code on laptops on different OSes to test that I didn’t break the project in an OS specific way. Let’s just say I wasn’t successful at that. This means that panicparse is going to be much more stable going forward.
I’ve removed the vendored code. As such Go 1.9.7 is now the minimum required version.
Why v2.0.1 instead of v2.0.0? The Go package paths were incorrect in v2.0.0, so I had to fix them in the source but the tag v2.0.0 was already in Go proxy sumdb, so it was too late for me to delete it.
Since I announced panicparse at Gophercon 2015, I invested hundreds of hours to improve the tool for all Go developers.
I hope you’ll appreciate the tool and it’ll help you diagnose issues faster. If so, please star the repository on github so I can better gauge the enthusiasm and see if it’s worth continuing to invest time in the project.