I have discovered that I can set the TTL in Varnish as follows in my VCL file:
sub vcl_fetch { # 1 minute set obj.ttl = 1m; } But what is the default setting (assuming the backend server is setting no cache-control header) ?
- Looks like I've found the answer: 120 seconds - this is in the default VCL logic.Ade– Ade2012-05-15 11:42:20 +00:00Commented May 15, 2012 at 11:42
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2 Answers
This is in the default template:
sub vcl_fetch { if (beresp.ttl <= 0s || beresp.http.Set-Cookie || beresp.http.Vary == "*") { /* * Mark as "Hit-For-Pass" for the next 2 minutes */ set beresp.ttl = 120 s; return (hit_for_pass); } return (deliver); } So, 120 seconds.
- Where did you find the default template?Neil– Neil2013-10-25 15:37:18 +00:00Commented Oct 25, 2013 at 15:37
- varnish-cache.org/docs/3.0/reference/vcl.htmlBart De Vos– Bart De Vos2013-10-25 19:11:06 +00:00Commented Oct 25, 2013 at 19:11
- There is a default.vcl that ships with varnish as of at least 3.0.3 which has all of the default config subroutines commented out in it. The 4.0 default config can be seen here: github.com/mattiasgeniar/varnish-4.0-configuration-templates/…th3morg– th3morg2015-08-07 16:43:40 +00:00Commented Aug 7, 2015 at 16:43
- 3This doesn't mirror my observations. It is true that the default ttl is 120 seconds, but the source of this number can't be that snippet. If it were, objects without a ttl would be marked as hit_for_pass, but they actually remain in the cache for 120 seconds.Kritzefitz– Kritzefitz2017-03-14 15:54:48 +00:00Commented Mar 14, 2017 at 15:54
- You'll find the source of the builtin vcl here - github.com/varnishcache/varnish-cache/blob/master/bin/varnishd/…. Use the
varnish-<version>tags to see the version for your Varnish release.Danny Thomas– Danny Thomas2019-05-06 17:50:02 +00:00Commented May 6, 2019 at 17:50
Default TTL can be passed through the varnishd command via the -t commandline switch and is probably sourced from a properties file on your filesystem. On the CentOS system I'm looking at it is set using DEFAULT_TTL from /etc/sysconfig/varnish.
You can see the live setting using varnishadm like so,
varnishadm param.show default_ttl Actually, following default VCL logic relates to non-cacheable objects.
sub vcl_fetch { if (beresp.ttl <= 0s || beresp.http.Set-Cookie || beresp.http.Vary == "*") { /* * Mark as "Hit-For-Pass" for the next 2 minutes */ set beresp.ttl = 120 s; return (hit_for_pass); } return (deliver); } means "if object is not cacheable - pass client requests for this object to backend directly and simultaneously for 2 minutes, do not queue them"
Read more at https://stackoverflow.com/questions/12691489/varnish-hit-for-pass-means
