Very strange varnish statistics after ESI activation

[Alexandre Thaveau]

Hi,

a few weeks ago, i asked the mailing list about my varnish statistics,
tracked under prometheus using varnish exporter (varnishstat wrapper).
2 weeks ago, one of our developpers activated ESI using these changes
(second modification is for a specific case but i put it in case of)
------------------------------------
# vcl_backend_response is called after a document has been successfully
retrieved from the backend
sub vcl_backend_response {
        set beresp.do_esi = true;
------------------------------------
    if(req.http.Cookie ~ "[^?]*custom_data_cookie=.*"){
    -    if(req.url !~ "^/([a-z]{2}/)$" && req.url !~ "^/([a-z]{2}/)(&|\?)"
&& req.url !~ "^/(&|\?)" && req.url != "/" && req.url !~
"^\/([a-z]{2}+\/)?((?!(ofertas|offres|aanbiedingen|angebote|offers)\b)[^\/]+\/)+([^\/]+\/)+([^\/]+\/)+([^\/]+\/)+$"){
    +    if(req.url !~ "^/([a-z]{2}/)$" && req.url !~ "^/([a-z]{2}/)(&|\?)"
&& req.url !~ "^/(&|\?)" && req.url != "/" && req.url !~
"^\/([a-z]{2}+\/)?((?!(ofertas|offres|aanbiedingen|angebote|offers)\b)[^\/]+\/)+([^\/]+\/)+([^\/]+\/)+([^\/]+\/)+$"
&& req.url !~ "^\/([a-z]{2}\/)?esi\/(.+)?"){
            return(pass);
        }
    }
------------------------------------
and configure our website menu to be edge side included (at maximum 50
combinations max using country and language used in parameter).

After this modification, multiple metrics changed in the supervision which
i do not understand :
- my number of varnish objects (main_n_object) went from 337 000 entries to
475 000 entries ... i really don't understand this since i thought my cache
memory
was full before and since we only added 50 ESI keys in the cache with this
update
- my cache hit (main_cache_hit) went from 2.5 % to 22% ... but pass, miss
and synth rates did not move, so the sum of all my varnish outputs are now
upper than 110 % ... (before they were equals to 100%)
- my backend output (beresp_hdrbytes) total dropped from 2MB to 85KB ...
however our websites are working fine

Can you help me understand this ?

Thanks

-- 
Alexandre THAVEAU
*04 72 89 22 11*
alexandre.thaveau at mister-auto.com <rgz at mister-auto.com>
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