I can't figure out, for the life of me, how to get varnish to ignore caching of 500 internal server errors. Basically, if someone hits varnish and is returned a 500 internal server error, I want varnish to not cache that page (set a 0s ttl/grace period?). I'm using varnish 3.0.3 and here's my VCL. By default, I want to cache the pages for 30 days.
sub vcl_fetch {
# Set 30-day TTL
set beresp.ttl = 2592000 s;
set beresp.grace = 15d; /* The max amount of time to keep object in cache */
if (beresp.status == 301 || beresp.status == 302) {
return (hit_for_pass);
}
# Serve pages from the cache should we get a sudden error and re-check in one minute
if (beresp.status >= 500) {
set beresp.grace = 1s;
set beresp.ttl = 1s;
return (hit_for_pass);
}
# Unset the "etag" header (suggested)
unset beresp.http.etag;
return(deliver);
}
So, in english: if a 500 internal server is returned... the X-CACHE should show a MISS. When I refresh the page, if it is still 500 internal server, then it should again show a MISS. If the page is successfully delivered, it should show a HIT.
By default Varnish will only cache the following status codes[1]:
Note that the first time the page is successfully delivered you will still get a MISS
[1] http://book.varnish-software.com/3.0/VCL_Basics.html#the-initial-value-of-beresp-ttl