How to log the name of backend that responded a request

Question

I'm using varnishncsa to log requests that are taking to long to be answered on my backend servers using the following command:

varnishncsa -F '%t "%r" %s %T' | awk '$7 > 10 {print}'

I was trying to add information on the backend name but this is not being displayed on varnishncsa output:

sub vcl_backend_response {
    std.log("backend_name:" + beresp.backend.name);
}

what I'm doing wrong?

score 0 · Accepted Answer · answered Mar 21 '17 at 18:35

0

It doesn't work for you because varnishncsa uses "client" mode by default. Enable it using -b switch.

Subsequently, this will work:

varnishncsa -b -F '%t "%r" %s %T %{VCL_Log:backend_name}x' | awk '$7 > 10 {print}'

You might want to check full explanation which includes additional optimization to query slow backend requests.

answered Mar 21 '17 at 18:35

Danila Vershinin

thanks! I'm using Varnish 4.1.1 and the varnishncsa command doesn't have the -b option: `varnishncsa: invalid option -- 'b'`; nice blog post, BTW. – hvelarde Mar 22 '17 at 19:28
Ah, bummer :) Works fine with Varnish 4.1.5 lol. – Danila Vershinin Mar 22 '17 at 20:32
You might then want to put your ```std.log``` statement in ```vcl_recv``` instead and log the value of ```req.backend_hint``` - this will work. – Danila Vershinin Mar 22 '17 at 20:34

1 Answers1