rbspy VS Nokogiri

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.

release planning: v1.16.0 · Issue #2897 · sparklemotion/nokogiri

What's holding me back from going all in with Crystal is I have a lot of pre-existing Ruby code, and porting Ruby code to Crystal can be tricky. For example, Crystal lacks an Enumerator class (aka generators) due to captured block semantics. I also wish the shards ecosystem was a little more mature; for example there's multiple HTML parsing libraries, but none have all of the features that Ruby's Nokogiri has. For new greenfield backend projects, I would totally use Crystal.

Welcome! Ruby isn't exactly "dying", but the hype/popularity is definitely fading. This is primarily because Ruby is no longer "new", most of Ruby's popularity came from Rails, and now Rails is no longer the "new hotness". However, Ruby still has lots of awesome features and lots of awesome other libraries and frameworks, such as the new fancy irb gem that uses reline, nokogiri, chunky_png, the async gems, Dragon Ruby, SciRuby, Ronin, and the new Hanami web framework.

great for hacking at xml

Mike has worked hard over the years to have Nokogiri come with its dependencies. It does come with libxml and all that is required.

From https://nokogiri.org

> These dependencies are met by default by Nokogiri's packaged versions of the libxml2 and libxslt source code, but a configuration option --use-system-libraries is provided to allow specification of alternative library locations.

Some authors work hard to have their tools do the right thing and consistently.

If the page is rendered as html you can use Nokogiri. It has great support and is pretty easy to get started with too.

And even now, pulling in a Java-based HTML5 parser is still probably easier than re-implementing in FFI, which is why I created https://github.com/sparklemotion/nokogiri/issues/2227 and would love to have this the conversation there if possible.