Re: [libmicrohttpd] How to disable the connection keep-alive header?

[silvioprog]

Ev,

I like all your explanations! :-)

I tested Node and it doesn't send any Connection header too, but I don't know why. BTW, I'm going to use as HTTP standards defines, but the `MHD_OPTION_CONNECTION_HEADER, "keep-alive",` would be very nice in some case like this:

=== the MHD initialization ===

 MHD_OPTION_CONNECTION_HEADER, iif(SomeOwnObject.KeepAlive, "Keep-Alive", "Close"),

=== the MHD initialization ===

It would define the default connection type (keep-alive or close) of all requests. :-)

On Sat, Jan 23, 2016 at 7:55 AM, Evgeny Grin <address@hidden> wrote:

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On 22.01.2016 20:27, silvioprog wrote:
> Is there some link where I can get it? I need this one to document it in
> my framework that uses MHD.
https://tools.ietf.org/html/rfc7230#page-52
- --- begin ---
A client that does not support persistent connections MUST send the
"close" connection option in every request message.

A server that does not support persistent connections MUST send the
"close" connection option in every response message that does not
have a 1xx (Informational) status code.
- --- end ---

https://tools.ietf.org/html/rfc7230#page-52
- --- begin ---
 o  If the "close" connection option is present, the connection will
    not persist after the current response; else,

 o  If the received protocol is HTTP/1.1 (or later), the connection
    will persist after the current response; else,
...
- --- end ---
So, if "Connection: " header is not present and protocol is HTTP/1.1 or
later, the connection must be persistent.

For better compatibility with older client MHD always add "Connection:
Keep-Alive" if persistent connection is used.

> I saw all headers from popular sites like Google
> <https://img42.com/dLL1P> and Facebook <https://img42.com/pUMyc>, and I
> didn't see the connection header. :-/ But it isn't a problem, because
> this sites uses HTTP 2.0, and I don't know if this one needs the
> connection header.
>
> BTW, it would be nice if the keep-alive/close value in the header could
> be chosen via some initialization flag, something like this:
>
> daemon =
>   MHD_start_daemon(MHD_USE_SELECT_INTERNALLY, PORT, NULL, NULL, &hr, NULL,
>   MHD_OPTION_CONNECTION_HEADER, "keep-alive",
>   MHD_OPTION_END);
It can be implemented, but close connection will waste system resources
as clients will repeatedly disconnect/connect to server. Better use
reasonable timeout value.


> Avoiding to handle it directly in the user callback request. And more:
>
>   (No declaration) -- uses MHD default, that's keep-alive
>   MHD_OPTION_CONNECTION_HEADER, "keep-alive", -- set keep-alive
>   MHD_OPTION_CONNECTION_HEADER, "close", -- set close
>   MHD_OPTION_CONNECTION_HEADER, NULL, -- undeclares Connection header,
> so the programmer do it by own risk
>
> What do you think? :-)
Without connection header, connection must be persistent for HTTP/1.1
(and later) and must be closed for HTTP/1.0.
"keep-alive" is not MHD's default, it's HTTP default.
"Connection" header allow to explicitly signal to client connection
mode, I can't see advantages of absence such header rather than
unnoticeable traffic lowering.

- --
Best Wishes,
Evgeny Grin
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--

Silvio Clécio