FastCGI

18.4.0 released Sep 25, 2023

FastCGI

You can run a Vely application as a server by using vf program manager. Your application will communicate with outside world using with FastCGI protocol.

You can access your server application by means of:

A web server (which is probably the most common way). You need to setup a reverse proxy, i.e. a web server that will forward requests and send replies back to clients; see below.
The command line, in which case you can use a FastCGI-command-line-client.
FastCGI-API, which allows any application in any programming language to access your server, as long as it has C linkage (by far most do). This method allows for MT (multithreaded) access to your application, where many client requests can be made in parallel.

Vely server runs as a number of (zero or more) background processes in parallel, processing requests.

Setting up reverse proxy (web server)

To access your application via a reverse proxy (i.e. web server), generally you need to add a proxy directive and restart the web server.

If you use Apache, you need to connect it to your application, see connect-apache-tcp-socket (for using TCP sockets) and connect-apache-unix-socket (for using Unix sockets).

If you use Nginx, you need to connect it to your application, see connect-nginx-tcp-socket (for using TCP sockets) and connect-nginx-unix-socket (for using Unix sockets).

Starting FastCGI server processes

Use vf, for example:

vf <app name>

which in general will start zero or more background resident process(es) (daemons) that process requests in parallel.

Connection timeout

In a heavy-load environment, a client's connection may be rejected by the server. This may happen if the client runs very slowly due to swapping perhaps. Once a client establishes a connection, it has up to 5 seconds by default to send data; if it doesn't, the server will close the connection. Typically, FastCGI clients send data right away, but due to a heavy load, this time may be longer. To set the connection timeout in milliseconds, set the following variable before starting the application server, for instance:

export "LIBFCGI_IS_AF_UNIX_KEEPER_POLL_TIMEOUT"="8000"
vf -w 1 <app name>

In this case, the timeout is set to 8 seconds.