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Comment by misframer | Hacker News Reader

I'm not a C++ programmer, and work mainly with Go. I'm curious to know if it is usual for C++ developers to implement their own event loops for network transports, as Diego has done here [0]. The other example I know is Replicant [1], which is used by HyperDex, and it uses a custom event loop too [2].

[0] https://github.com/logcabin/logcabin/tree/master/Event

[1] https://github.com/rescrv/Replicant

[2] https://github.com/rescrv/busybee

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LogCabin uses its event loop for network operations but then hands requests off to threads to process. I started out with libevent2, but the problem is it doesn't deal with having multiple threads very well (error-prone and inefficient). It's also not as well-documented as the man pages for epoll, so I ended up using epoll directly instead. What was really lost in the libevent2 -> epoll conversion was platform independence, but I think it might be better to get that back through well-placed #ifdefs or relying on some other library; I wouldn't go back to libevent2.

> What was really lost in the libevent2 -> epoll conversion was platform independence

Did you consider libuv?

I guess the answer is no, I haven't really looked at it. Anyone have experience with it in a large-ish project outside of Node?

Yes -- it is very straightforward to use and "just works". (It is also used in a similar way as found in Node in the luvit project: https://github.com/luvit/luvit)

We're using libev (actually libev++ which is cross-platform, has a decent underlying C impl, and a C++ bridge API). It seems to work well and is fast and cross platform. It can be a little tricky to figure out what is going on with the C++ API sometimes due to how the author tacked it on using macros.

This is fairly common. I've done professional work with Go and C++ and this is one of the biggest reasons I like Go over C++. C++'s concurrency primitives aren't quite good enough so you always need to build something on top of them. Using a library in C++ often requires grokking how it does concurrency and reconciling that with the way your code does concurrency. In Go everyone uses goroutines so you can very quickly understand how to use libraries.

C++ developers don't make their own event loop. They use epoll which is provided by the kernel. That is still the area the C/C++ ( and Rust ) have over Go, they can use syscalls without requiring the goodwill of one of the language developers.

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