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Ade
Asked: 2012-05-16 03:02:47 +0800 CST

Varnish Cache - default TTL?

  • 772

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) ?

cache varnish ttl

2 Answers

  1. 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

    • 34
  2. Best Answer

    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.

    • 24