Varnish 6 missing requests for same URL coming from different browsers - varnish

Question

This is how my varnish.vcl looks like.
vcl 4.0;
import directors;
import std;
backend client {
.host = "service1";
.port = "80";
}
sub vcl_recv {
std.log("varnish log info:" + req.http.host);
# caching pages in client
set req.backend_hint = client;
# If request is from conent or for pages remove headers and cache
if ((req.url ~ "/content/") || (req.url ~ "/cms/api/") || req.url ~ "\.(png|gif|jpg|jpeg|json|ico)$" || (req.url ~ "/_nuxt/") ) {
unset req.http.Cookie;
std.log("Cachable request");
}
# If request is not from above do not cache and pass to Backend.
else
{
std.log("Non cachable request");
return (pass);
}
}
sub vcl_backend_response {
if ((bereq.url ~ "/content/") || (bereq.url ~ "/cms/api/") || bereq.url ~ "\.(png|gif|jpg|jpeg|json|ico)$" || (bereq.url ~ "/_nuxt/") )
{
unset beresp.http.set-cookie;
set beresp.http.cache-control = "public, max-age=259200";
set beresp.ttl = 12h;
return (deliver);
}
}
# Add some debug info headers when delivering the content:
# X-Cache: if content was served from Varnish or not
# X-Cache-Hits: Number of times the cached page was served
sub vcl_deliver {
# Was a HIT or a MISS?
if ( obj.hits > 0 )
{
set resp.http.X-Cache-Varnish = "HIT";
}
else
{
set resp.http.X-Cache-Varnish = "MISS";
}
# And add the number of hits in the header:
set resp.http.X-Cache-Hits = obj.hits;
}
If I am hitting a page from same browser netwrok tab showing
X-Cache-Varnish = "HIT";
X-Cache-Hits = ;
Lets say if I hot from chrome 10 times this is what I get
X-Cache-Varnish = "HIT";
X-Cache-Hits = 9;
9 because first was a miss and rest 9 were served from cache.
If I try incognito window or a different browser it gets its own count starting from 0. I think somehow I am still caching cookies. I could not identify what I am missing.
Ideally, I want to delete all cookies for specific paths. but somehow unset does not seem to be working for me.

Answer 1

If you really want to make sure these requests are cached, make sure you do a return(hash); in your if-statement.
If you don't return, the built-in VCL will take over, and continue executing its standard behavior.
Apart from that, it's unclear whether or not your backend sets a Vary header which might affect your hit rate.
Instead of guessing, I suggest we use the logs to figure out it.
Run the following command to track your requests:
varnishlog -g request -q "ReqUrl ~ '^/content/'"
This statement's VSL Query expression assumes the URL starts with /content. Please adjust accordingly.
Please send me an extract of varnishlog for 1 specific URL, but also for both situations:
The one that hits the cache on a regular browser tab
The one that results in a cache miss in incognito mode or from a different browser
The logs will give more context and explain what happened.