BBlack has submitted this change and it was merged.

Change subject: N-hit-wonder: 4-hit, and improve filtering
......................................................................


N-hit-wonder: 4-hit, and improve filtering

In addition to raising this from 2-hit-wonder to 4-hit-wonder,
there's also some changes to the filtering here: (1) Don't pay
attention to beresp.ttl at all (seems pointless) and (2) Filter on
local cache disposition of "miss" (as opposed to "pass" or "int"),
mostly so this doesn't interfere with natural or hit-for-pass
passes.

Bug: T144187
Change-Id: I89cf391483547ba259285925f5462d079dd60107
---
M modules/varnish/templates/upload-frontend.inc.vcl.erb
1 file changed, 5 insertions(+), 10 deletions(-)

Approvals:
  BBlack: Looks good to me, approved
  jenkins-bot: Verified



diff --git a/modules/varnish/templates/upload-frontend.inc.vcl.erb 
b/modules/varnish/templates/upload-frontend.inc.vcl.erb
index f9cac18..e9f1bd0 100644
--- a/modules/varnish/templates/upload-frontend.inc.vcl.erb
+++ b/modules/varnish/templates/upload-frontend.inc.vcl.erb
@@ -77,18 +77,13 @@
        }
        <%- end -%>
 
-       // Two-hit-wonder experiment: if the immediate backend does not indicate
-       // hit/2 or higher, deliver the object as normal but do not create a new
+       // Four-hit-wonder experiment: if the immediate backend does not 
indicate
+       // hit/4 or higher, deliver the object as normal but do not create a new
        // cache entry of any kind.  We start caching in the frontend when an
-       // object is accessed for the 3rd time across all frontends in this DC.
-       // The ttl>3600 check is to ensure we don't apply this to any short-TTL
-       // edge cases we're not thinking of.
-       // We probably want to either back out this experiment later or improve
-       // on it, especially re: multiplying backend requests when warming a
-       // cold cache.
+       // object is accessed for the 5th time across all frontends in this DC.
        if (beresp.status == 200
-            && beresp.http.X-Cache-Int !~ " hit/([2-9]|[0-9]{2,})$"
-            && beresp.ttl > 3600s) {
+            && bereq.http.X-CDIS == "miss"
+            && beresp.http.X-Cache-Int !~ " hit/([4-9]|[0-9]{2,})$") {
                set beresp.ttl = 0s;
                <%- if @varnish_version4 -%>
                set beresp.uncacheable = true;

-- 
To view, visit https://gerrit.wikimedia.org/r/311726
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings

Gerrit-MessageType: merged
Gerrit-Change-Id: I89cf391483547ba259285925f5462d079dd60107
Gerrit-PatchSet: 1
Gerrit-Project: operations/puppet
Gerrit-Branch: production
Gerrit-Owner: BBlack <bbl...@wikimedia.org>
Gerrit-Reviewer: BBlack <bbl...@wikimedia.org>
Gerrit-Reviewer: Ema <e...@wikimedia.org>
Gerrit-Reviewer: jenkins-bot <>

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