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Subject: Re: [boost] [asio-users] [http] Formal review of Boost.Http
From: Lee Clagett (forum_at_[hidden])
Date: 2015-08-07 23:49:01

Sorry for any duplicates and top posting, but I didn't reply-all, so boost
got dropped (which was probably more important). And this likely ruins some
mail clients (again sorry!).

On Fri, Aug 7, 2015 at 11:10 PM, Lee Clagett <forum_at_[hidden]> wrote:

> On Fri, Aug 7, 2015 at 6:29 PM, Vinícius dos Santos Oliveira <
> vinipsmaker_at_[hidden]> wrote:
>> 2015-08-07 12:53 GMT-03:00 Niall Douglas <s_sourceforge_at_[hidden]>:
>>> I do not believe Http is ready for peer review for these reasons, and
>>> I personally would urge you withdraw it until you have fixed these
>>> issues and then come back to us. If you do not withdraw it, I will
>>> vote for rejection.
>> ...[large snip]...
>>> * I don't understand why you cannot issue more than one async read at
>>> a time nor async write at a time. In something like pipelined HTTP
>>> that seems like a very common pattern. I smell a potential design
>>> flaw, and while the docs mention a "queue_socket" I can't see such a
>>> thing in the reference section.
>> Too much synchronization and buffering.
>> The pipeline has the following requests:
>> A => B => C
>> If I were to allow replies to request B, the design would be more
>> complex, increasing the difficult to implement alternative backends and
>> everyone's life. Also, the reply to request B cannot actually be sent while
>> the reply to request A is on hold. This means that the whole response to
>> request B would need buffering and if response B is a video live stream,
>> this means an implicit (the user cannot know) crash after an unfortunate
>> memory exhaustion. I couldn't claim a **lightweight** server if this
>> excessive buffering was to occur. I couldn't claim the project is
>> appropriate for embedded devices if I had chosen the buffering approach.
>> It's a trade-off. I should write about it in the "design choice" of the
>> documentation.
>> HTTP/2.0 does have proper multiplexing and it can be more useful to
>> respond several requests without "head of line blocking".
>> A queue socket is a concept, I don't provide one. I can look into how
>> make the documentation less confusing by adding a page exclusively
>> dedicated to explain the problem it solves. Would that work for you?
> FWIW it should be possible to do client and server side pipelining with
> this design right now. The reads and writes of the HTTP Socket concept
> should be (and currently are by `basic_socket`) handled independently.
> Since the notification for a write completion is based on the lower layer
> write completion, and NOT whether a HTTP response was received, multiple
> (pipelined) requests should be possible by a client. Similarly, this design
> should allow servers to handle pipelined requests in parrallel. Providing a
> framework for client or server pipelining will require more work, and
> should probably not be a part of the Socket concept. In fact -
> I think the ServerSocket concept should be removed entirely. The
> `http::basic_socket<...>` models both concepts, so theres lots of server
> specific code in it, which seems confusing to me (is this really a "basic"
> socket?). I think standalone functions for typical client and server
> operations can be implemented as "composed" operations similar to
> `asio::async_write`. The documentation will have to be explicit on what the
> composed function is doing so that users know whether the Socket concept
> has outstanding reads or writes (and therefore cannot do certain operations
> until the handler is invoked). In fact, if there is a server operation that
> _cannot_ be done with the Socket concept, then the concept probably needs
> to be re-designed.
> Lee

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