FastCGI is designed to multiplex requests over a single connection, so
ideally the server can open only one connection per worker to the
FastCGI application and that's that.
Doing this kind of multiplexing makes the code harder to follow and
easier to break/leak etc on the gmid side however. OpenBSD' httpd
seems to open one connection per client, so why can't we too?
One connection per request is still way better (lighter) than using
CGI, and we can avoid all the pitfalls of the multiplexing (keeping
track of "live ids", properly shut down etc...)
This is a big change in how gmid handles I/O. Initially we used a
hand-written loop over poll(2), that then was evolved into something
powered by libevent basic API. This meant that there were a lot of
small "asynchronous" function that did one step, eventually scheduling
the re-execution, that called each others in a chain.
The new implementation revolves completely around libevent'
bufferevents. It's more clear, as everything is implemented around the
client_read and client_write functions.
There is still space for improvements, like adding timeouts for one, but
it's solid enough to be committed as is and then further improved.
This changes the fastcgi implementation from a blocking I/O to an
async implementation on top of libevent' bufferevents.
Should improve the responsiveness of gmid especially when using remote
fastcgi applications.
we need to delete the events associated with the backends, otherwise
the server process won't ever quit.
Here, we add a pending counter to every backend and shut down
immediately if they aren't handling any client; otherwise we try to
close them as soon as possible (i.e. when they close the connection to
the last connected client.)
Not production-ready yet, but it's a start.
This adds a third ``backend'' for gmid: until now there it served
local files or CGI scripts, now FastCGI applications too.
FastCGI is meant to be an improvement over CGI: instead of exec'ing a
script for every request, it allows to open a single connection to an
``application'' and send the requests/receive the responses over that
socket using a simple binary protocol.
At the moment gmid supports three different methods of opening a
fastcgi connection:
- local unix sockets, with: fastcgi "/path/to/sock"
- network sockets, with: fastcgi tcp "host" [port]
port defaults to 9000 and can be either a string or a number
- subprocess, with: fastcgi spawn "/path/to/program"
the fastcgi protocol is done over the executed program stdin
of these, the last is only for testing and may be removed in the
future.
P.S.: the fastcgi rule is per-location of course :)
Omar Polo