lexbor VS rbspy

Project is deprecated in favour of the same developer's lexbor project[0].

[0]: https://github.com/lexbor/lexbor

It supports both CSS selectors and XPath like Nokogiri, but with separate engines - parsing and CSS engine by Lexbor, XPath engine by libxml2. (Nokogiri internally converts CSS selectors to XPath syntax, and uses XPath engine for all searches).

An HTML parser, probably the simplest relatively modern example I could find is 1MB https://github.com/lexbor/lexbor (haven't used it, but might look more into it now that I know it exists.)

Lazyweb link: https://github.com/rushter/selectolax

although I don't follow the need to have what appears to be two completely separate HTML parsing C libraries as dependencies; seeing this in the readme for Modest gives me the shivers because lxml has _seen some shit_

> Modest is a fast HTML renderer implemented as a pure C99 library with no outside dependencies.

although its other dep seems much more cognizant about the HTML5 standard, for whatever that's worth: https://github.com/lexbor/lexbor#lexbor

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> It looks like the author of the article just googled some libraries for each language and didn't research the topic

Heh, oh, new to the Internet, are you? :-D

Lexbor is here: https://github.com/lexbor/lexbor

Well, regarding HTML5, what I've found was libxml (does not support tag-soup HTML5), https://github.com/lexbor/lexbor, for which I was unable to find good documentation ( see https://lexbor.com/docs/lexbor/#dom), Apache Xerces (appears to not support tag-soup HTML5 as well), and Gumbo, which does not appear to be active and to support selectors and XPath (although there are libraries that add that).

I think we've all (mostly?) tried it. It really is the Wild West of the web when you're trying to parse other people's HTML, though.

I've played around with this parser which is extremely quick. https://github.com/lexbor/lexbor

I’m glad to have the opportunity to contribute to an open-source project that is used by thousands of people. Hopefully, we will speed up Nokogiri (or XML parser it uses) to match the performance of html5ever or lexbor at some point in the future. 800 ms to extract data from HTML is still too much.

We used rbspy to generate the flamegraph:

You could use rbspy to profile the EventMachine process as it's doing the workload, and try to see there where most of the time is being spent.

Not sure what your issue is and you got some of this info from strace, but FYI rbspy can also help profile where a running Ruby process is spending its time: https://rbspy.github.io/. I think it's a little more helpful than strace in that it should bring it back to Ruby code rather than just showing the raw syscalls.

Even the most general profiler tool will show you each statement's accumulated time. These are called statistical profilers and give you a panoramic view of what the test is doing. An example of such a profiler is rbspy:

As a result, you need to craft a specific routine for each interpreter runtime (in some cases, each version of that runtime) to obtain symbol information. Educated eyes might have already noticed, it's not an easy undertaking considering the sheer amount of interpreted languages out there. For example, a very well known Ruby profiler, rbspy, generates code for reading internal structs of the Ruby runtime for each version.

For production, it depends on what the process is built with. There are possibly better tracing tools than just strace. For example Java has JMX, Go has pprof. There's also things like rbspy for Ruby.

I was a bit surprised to find out that the tool used to generate the flamegraph for Ruby (rbspy [1]) is written in Rust. lol

[1] https://github.com/rbspy/rbspy

Maybe https://github.com/rbspy/rbspy would allow you to profile the running ruby process handling web sockets?

c function is not very helpful to find the performance problem, so we dug deeper.