Using inline C to extend VarnishΒΆ

(Here there be dragons. Big and mean ones.)

You can use inline C to extend Varnish. Please note that you can seriously mess up Varnish this way. The C code runs within the Varnish Cache process so if your code generates a segfault the cache will crash.

One of the first uses of inline C was logging to syslog.:

# The include statements must be outside the subroutines.
        #include <syslog.h>

sub vcl_something {
                syslog(LOG_INFO, "Something happened at VCL line XX.");

To use inline C you need to enable it with the vcc_allow_inline_c parameter.