Java Flight Recorder support

[vasi]

Would y'all be interested if I implemented JFR support? There's not really any official format documentation, but there's some basic docs here and an Apache licensed Java parser to steal from.

Unfortunately it's a binary format, but there's good support for binary reads in JS nowadays, so it ought to be possible.

Another complication is that JFR files can support multiple concurrent profiles, for example both an alloc and CPU profile in the same file. It's not clear what we should do given such a file.

[parttimenerd]

Reading the JFR format in JS is considerable effort and possibly leads to maintenance issues.

[parttimenerd]

A converter with basic support can be found here: https://github.com/parttimenerd/jfrtofp

@jlfwong is there the possibility to add this to your converter pages?

[beatbrot]

So I have locally hacked together a version of speedscope that supports Java Flight Recording. Unfortunately, I need a dependency to a fork of my jfrview project. Would adding a dependency that uses WASM be acceptable to you @jlfwong?

[jlfwong]

@beatbrot can you push your fork so I can take a look? I'm potentially open it, just depends on the specifics and what it implies about bundling configuration. It would definitely need to be lazy loaded

[beatbrot]

@jlfwong You can find my fork here: https://github.com/beatbrot/speedscope/tree/experimental-jfr

The referenced "jfrview" library is a lightly modified version of my https://github.com/beatbrot/jfrview project (see branch experimental-jfr).

If we wanted to add this, I would have to publish my library to NPM, which wouldn't be a problem to me :)

Edit: Forgot to push the required esbuild update. Now it should work!

[jlfwong]

This looks reasonable to me, with two changes:

1. Please make the esbuild upgrade into a separate PR, and let's get that landed first
2. The wasm ball is going to need to be lazy loaded so we don't block initial load on the download of the wasm ball for this

[parttimenerd]

I made a PR to link to my JFR to speedscope converter tool: #532

[jlfwong]

Going to close this as done w/ #533