Hi,
I’m trying to configure vcl_fetch for a particular scenario. In certain
situations, say a particular aspect of a page fails to render correctly and we
don’t want this to be cached in varnish, the backend server is appending a
particular header to the response, in this case “X-SP-NoCache: yes”. In
vcl_fetch I am then checking for this header, and switching to pass mode. The
problem is, when the header is then removed from that page, it still continues
to pass it instead of delivering it (it doesn’t get inserted into the cache).
It goes as follows (assuming a new varnish instance has just been started):
Action X-SP-NoCache
X-Cache (set in vcl_deliver)
Browser to Url yes
Miss
Refresh page yes
Miss
Change X-SP-NoCache header no
Miss
Refresh page no
Miss
Purge page with varnishadm no
Miss
Refresh page no
Hit
The vcl_fetch function looks as follows:
Sub vcl_fetch {
If (beresp.http.X-SP-NoCache ~ “(?i)yes”) {
Return (pass);
}
//Other code is included in here, passes control to deliver or pass
depending on other criteria
}
The thing that’s confusing me, and that’s leading me to believe it isn’t my vcl
code that’s the problem, is that flushing the cache is fixing the issue. I
don’t understand how flushing the cache can affect the behaviour of any page
which isn’t currently stored in the cache? I’m running varnish-2.1.3 if that’s
relevant. Any help would be greatly appreciated.
Thanks,
Connor Walls
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