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From Dean Gaudet <dgau...@arctic.org>
Subject Re: [PATCH] select-thread-hybrid-01.patch
Date Tue, 18 May 1999 17:31:10 GMT
On Tue, 18 May 1999, Ryan Bloom wrote:

> 
> > I don't think the abstraction is worth keeping -- you had only one
> > "message type" essentialy.
> 
> The abstraction is necessary.  There are some operating systems that don't
> want to use a complex messaging system like what you are implementing.  I
> am thinking of one platform already that has already expressed an interest
> in using another method for accepting connections.  Plus, we most
> definately don't want the server on a non-threaded system to use the same
> accept model as a threaded platform.  Everything I have heard from the
> group is that the hybrid server must be able to run in both thread-only
> and process-only mode.  The accept model abstraction makes this possible.

The abstraction is still at the wrong level... it certainly shouldn't
be in http_main.c.  Yes I know about those other systems.  It should be
easy to handle them by not sending the messages.  I was hoping to have
an example for you by now.

Just think of those other systems as systems where SO_SNDBUF is
infinite... remember I said that I wasn't going to punt back to the event
loop when the response fits in the kernel buffers?  That means that the
response handler will run in a "worker thread".  The code should be pretty
similar.

For example, sending a memory mapped region (mmap or otherwise), here's
the interface I'm currently playing with:

    typedef struct {
	conn_rec *conn;
	void *mm;
	size_t length;
	void *uap;
	void (*complete)(void *uap, int bytes_sent);
    } ap_async_send_mmap_data;

    API_EXPORT(void) ap_async_send_mmap(ap_async_send_mmap_data *);

The handler allocates the structure, sets up the parameters, and
calls ap_async_send_mmap.  Then it returns OK.

The complete function is called in the future when the operation has
completed.  At this point, another ap_async_send_mmap() could be performed
(for example, handling range requests).

Folks familiar with async programming should recognize this... it's
a pretty standard method.  It doesn't require anything special other
than a few conventions.

> I really hope that when you say fds, you mean sds.  If you require all fds
> to be non-blocking, including those actually referring to files on disk,
> we have a problem.  There are too many platforms that do not support
> non-blocking fds for files on disk.

No I don't require all fds to be non-blocking.  Not even unix supports
non-blocking disk file fds.  That's why I gave separate cases for sending
a file versus sending a pipe (i.e. handling a cgi or other external
process through a pipe/socket). 

Dean


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