a) Show me the code to start with, don't send me digging for it. A SimpleController example as the very first thing would help give a feel for the project, and makes me more likely to consider the project.
b) If there's an easier way (like the drogon_ctl utility at the start of Quickstart [0]), show that first, and the more detailed way second.
Other than that, it looks great. I've used libmicrohttpd a few times, so a bit less of an overhead always looks great.
This is cool, and I like it. Very Haskell like, which is a compliment in my book.
But one thing that surprises me is that folks are essentially sleeping on HTTP/2. HTTP/2 is just a hell of a lot better in most every dimension. It's better for handshake latency, it's better for bandwidth in most cases, it's better for eliminating excess SSL overhead and also, it's kinda easier to write client libraries for, because it's so much simpler (although the parallel and concurrent nature of connections will challenge a lot of programmers).
It's not bad to see a new contender in this space, but it's surprising that it isn't http/2 first. Is there a good reason for this? It's busted through 90% support on caniuse, so it's hard to make an argument that adoption holds it back.
The reason is that HTTP/2 will be short-lived. Most of its potential (protocol multiplexing, mainly) is wasted because it still runs over TCP/IP. HTTP/3 will correct that with QUIC. I think we can except HTTP/3 to really see widespread adoption.
HTTP/1.1 will remain ubiquitous though because there's a gazillion box that only speaks that.
To the extent that HTTP/3 is faster/cheaper/better than its predecessors, it should allow ads to be served more cheaply. Combine that with support in the dominant browser (and why wouldn't they, after all they did basically invent it and they have a vested interest in serving ads efficiently) and I'd say HTTP/3 has a pretty good shot at success.
> To the extent that HTTP/3 is faster/cheaper/better
This is rather questionable assumption. For almost everyone in the world it's not faster/cheaper/better than HTTP/1.1, definitely not worthy enough to even bother with it. So, the only way it can get anywhere is if Google abuses its position and forces everyone to adopt it. Which they probably won't do for such a silly thing, they get more out of it by coming up with more useless mediocre "faster/cheaper/better" protocols HTTP/[4567], because this pressures competition to waste resources on that, instead of on something that can compete with Google.
One way to get around this is to use HAProxy as a middleman where it can handle HTTP2 concurrent connections on the frontend and then connect to the HTTP1.1 webservers on localhost on the backend so that you don't have to pay the big TCP connection latency.
Right, and this is "better" but if you start handling significant volume you're going to want HTTP/2 behind your proxy. Envoy does this, and it's a basically free way to just get more out of your hardware and network.
Not necessarily because let's say your backend server is multi-threaded and assigns each connection to its own thread for DoS safety. Now with HTTP2, you will make one connection to the backend server even though you are multiplexing those requests they’re still being served serially by one thread+socket. Even if you Demux and use threadhandlers you have to remux and are still limited to the single socket.
Now if HAProxy makes multiple connections to the backend each one gets served by its own thread+socket and that's going to load much faster because at the very least it's going to get more attention from the OS. Furthermore, if you use the keepAlive header, and set long timeouts, then you don’t even have to pay the connection penalty. So essentially you’ve shifted thread management to HAProxy by virtue of its parallel connections which keeps the webserver code pretty simple. And in a C++ program simplicity is key to correctness
I'm not sure I agree with most of this post. Firstly, a userland socket mux/demux implementation isn't such an insurmountable challenge. It's essentially the core of a good http/2 implementation. If you've got a good HTTP/2 implementation, you've necessarily got a good mux/demux solution.
> Now if HAProxy makes multiple connections to the backend each one gets served by its own thread+socket and that's going to load much faster because at the very least it's going to get more attention from the OS.
I'm not sure what you're basing this on. What is the technical definition of "more attention from the OS." If anything, limiting things down to a single process over one connection will improve latency. It'll can help minimize memory copies if you get volume because you'll get more than one frame per read (and you certainly aren't serving a L>4 protocol out of your NIC). Most importantly, it'll remove connection establishment and teardown costs. These aren't free.
Now, if you really are loading backends so that responsiveness is a problem, you'll need to appeal to whatever load balancing solution you have on hand. But most folks agree that this is faster.
> Furthermore, if you use the keepAlive header, and set long timeouts, then you don’t even have to pay the connection penalty.
But you still have head-of-line blocking, so you're still spamming N connections per client to get that concurrency factor. Connections aren't free, they have state and take up system resources. You'll serve more clients with one backend if you take up less resources per connection.
> So essentially you’ve shifted thread management to HAProxy by virtue of its parallel connections which keeps the webserver code pretty simple.
I don't think this is true at all. If you want to serve connections in parallel or access resources relevant to your service in parallel, you're going to need to do that. You can of course choose to NOT do this and spam a billion processes rather than use concurrency.
> And in a C++ program simplicity is key to correctness
I don't think this is unique to C++, but I'm also not sure it's really relevant here. From an application backend's perspective, it's very much the same model. They need a model that supports re-entrant request serving.
First let me give some background. In the beginning there was HTTP1.0
where you send a request recieve a reply and then terminate the connection. A TCP connection required 3 round trip packets for every connection + a reques and a recieve meant that 60% of the delay was mearly getting ready to talk.
Http1.1 brought pipelining where you could use the keepalive header and send req1, req2, recN and then expect to recieve reply1, reply2, replyN. The replies are expected in the order they are requested.
Http2 adds a bunch of things. For one, the requests are in a binary format instead of a text in order to acheive better compression. Another thing is that it allows multiplexing. This is different from pipelining because now you can recieve replies out of order which allows small files not to get stalled out by large files.
However, HAProxy will Demux the http2 requests and separate them into multiple parallel connections to the backend server where each connection supports pipelining so as not to close immediately. Each request will use a connection that’s free (ie doesnt already have a pipelined req in progess) so this is effectively the same as http2 multiplexing since HAProxy will send them back to the client in the order they are recieved from the backend (which isnt necessarily the requested order aka multiplexed)
The benefit here is that
1) If you have multiple webservers, they dont have to each deal with the muxing/demuxing of streams and converting the binary to http.(might be possible to skip binary translation but code will be ugly)
2) If you have parallel connections each using threatpools to handle each request stream then you could start running into thread contention problems
3) You protect your C++ webservice with a battle tested service like HAProxy
One possibility is that HTTP/2 is much more work to implement, and since it isn’t /absolutely/ required for base “serve a thing” functionality, it maybe be left to be implemented later.
I'm not sure that "HTTP/3 is about to overtake HTTP/2" is a very fair statement given how many years it took load balancers to start supporting HTTP/2.
HTTP/3 (QUIC) is genuinely exciting and I'm very eager to see it. But given it's even more different from http/2 than http/2 is from http 1.1, it's probably gonna be another 3-4 years before we see good load open source balancer performance in front of it.
It conforms better to the async model that JavaScript loves. For everyone outside the single largest deployment in history, it's simpler because it's a smaller spec.
I see your point, though I'd very much prefer if we could split the stack into application server > http server > SSL terminating reverse proxy by default. That includes HTTP/2 handling in the proxies task list. That would split concerns way more elegantly than having to replicate logic between http and https modules.
By that argument, they should get cracking on HTTP/3 already. :)
Even though HTTP/2 is usable, adoption is still low (last I checked it was around 25%), and any server that supports 2 needs to support 1 for backwards compatability. It's also more complicated to implement, so I can see why you'd want to start with HTTP/1.
HTTP/2 has support on over 90% on caniuse, which is a decent approximation of what most folks selling products here will see. The browsers that don't support it aren't the sort we really care that much about anyways unless we're building a bank or something, in which case suffering is your mandate anyways.
As for client libraries for APIs, it's a non-issue. There's plenty of flexibility on backends.
I'm not saying you'd skip "HTTP/1" but I certainly wouldn't put a lot of effort into it.
You lose out bigtime between your revproxy and your backends. You might as well abandon it entirely and go with grpc streaming or thrift.
Revproxies are essentially awful, ugly lynchpins in your distributed architecture. You want to be as low as you can afford to be on utilization for them, because if they have a bad day you have no product.
I didn't say you wouldn't have a proxy. I said you want to have as few as you possibly can for volume and redundancy, because they're a centralized point of failure in your architecture and they have to scale over your entire infrastructure.
I am certainly NOT advocating for their lack. I'm not even sure how that could realistically work.
If you really want a security story, you shouldn't be looking into a C++ server. That's a very false sense of security, there is no way to guarantee memory safety.
Absolutely not true for C++. The language was invented to guarantee memory safety, like Rust was. (The fact that people ignore the safety features when coding is irrelevant, people liberally throw 'unsafes' around in Rust and Haskell too.)
C++ wasn't invented to be safe in the same way as Rust or Ada, whose author's saw state of the art safety as a critical tenant of the language. Stroupsoup was, I believe, mostly interested in making C more suitable for large software engineering projects and was more interested in better abstractions, which could lead to better safety.
The fact that people can ignore the safety features is the point. Unsafe is a contract, and it only opens a small number of extra "features". It forms the axioms of a proof the your code correctly uses memory. C++ is essentially just patched with safer abstractions, some of which are major improvements, but there is no proof, no rigorous check for safety until runtime from asan or a fuzzer, or other tools that aren't a part of core C++.
The biggest issue with the safety of C++, however, is the size of the language. It has become so big and so complicated, and the rules that govern things we take for granted like function name lookups are horrendously unintuitive and lead to unintended consequences.
The language was invented so that Bjarne after his experience having to rewrite Simula into BCPL, never had to go through such a low level language again in his life.
Plenty of interviews where he states this, including some of his books.
leads to undefined behavior (aka the standard says the program can delete your hard drive) if x is too big, that's not a language that guarantees memory safety.
According to the spec, it can lead to all the same problems that any UB leads to, including all the problems that any memory unsafety leads to. The code is allowed by the spec to cause memory unsafety.
But to list some direct memory unsafety possibilities: indexing off the end of an array, indexing off the end of a vector, dereferencing a bad pointer, dereferencing a null pointer, dereferencing a bad iterator, double delete.
I have a big amount of love for C++, but even if the user of this framework knows about security, I would really recommend to not use it.
The risk of security issues of such framework, since it uses C++, might be quite high. I'm not into security a lot, so don't trust my word, but I'd be very cautious.
Generally, I guess higher performance means lower security.
I like it, but the API for defining HTTP endpoints seems messy compared to, say, Flask or ExpressJS. Is there any particular reason it is done this way vs something syntactically cleaner, like:
The method in the readme file is for decoupling. Imagine a scene with dozens of path handlers. Isn't it better to disperse them in their respective classes?
Of course, for very simple logic, the interface you are talking about is really more intuitive, I will consider adding such an interface. Thank you for your comment.
> Use a NIO network lib based on epoll (kqueue under MacOS/FreeBSD) to provide high-concurrency, high-performance network IO
What is "NIO" here? I am familiar with NIO as New Input-Output from Java, which was the extension of the standard library to cover asynchronous I/O. Is the author using "NIO" to mean asynchronous IO? Their use of '"JSP-like" CSP file' elsewhere hints at a Java background.
Good question！
If the type of the parameter of callback is an r-reference, users must move resp into the callback. Note that the resp is a shared_ptr, which means callback can reuse the buffer or do anything to the resp object and copying smart pointers does not require too much cost.
Why not just wrap libevent or some other battle tested network poller?
Also, this would be super cool if it were in Rust. As it stands writing web services in C++ is basically programming malpractice at this point. Would love to see the author contributing to tokio or hyper and helping us get rid of all this legacy inheritancey impl junk.
I am unapologetic about the truth. The calculus engineers employee that leads them to defer the safety of user facing software for the familiarity of C++ has to stop.
I don't claim that Rust is bulletproof. You still have to verify the axiomatic unsafe sections of your code. There can still be bugs in Rust itself, or logical errors in your programs. What I do claim is Rust is a giant leap forward over C++, which is an inadequate tool to write software end users will use. As society continues to rely more and more on software, as it becomes the thing that we stake our lives on, we have a moral responsibility to modernize our tools.
It would be much better to use asp.net core over Rust or Drogon. Safe, fast, easy to develop for, easy to hire engineers for, better for actually building a product quickly with fewer bugs.
I'm comparing using Rust versus C++ to build something like Drogon. We're talking about tools to build high performance infrastructure, which is completely different than using the infrastructure from an application developers perspective.
Nim is playing much of the same tune of D, which ultimately failed to gain the needed traction to be a real competitor. It's already ruined by inheritance and the desire to please everyone with the multi-paradigm, take it or leave it GC, compile to everything approach.
Literally anything would be better than C++ at this point though. I'd take D or Nim over C++ in a heartbeat, which is drowning in the weight of its own specification, coupled with a desire to keep programmers in the dark ages of memory safety by convention and the C preprocessor. It's also impossible to find a C++ code base that doesn't have some sort of safety issue even with smart pointers and RAII. Fuzzing, testing, and trying to patch things up simply isn't enough.
The software landscape has changed, there are now more reasons than every to chose a language based on safety and efficiency than can run everywhere than ever before.
It's possible and actual not difficult to write memory-safe C++ code. In the last several years the C++ projects I worked on had close to zero memory issues (I cannot recall any). I think with the advancements of C++14/17 memory issues is a largely solved problem.
a) Show me the code to start with, don't send me digging for it. A SimpleController example as the very first thing would help give a feel for the project, and makes me more likely to consider the project.
b) If there's an easier way (like the drogon_ctl utility at the start of Quickstart [0]), show that first, and the more detailed way second.
Other than that, it looks great. I've used libmicrohttpd a few times, so a bit less of an overhead always looks great.
[0] https://github.com/an-tao/drogon/wiki/quick-start