How to debug VCL in varnish?

Question

How can I print a log in VCL?

Can I print log info on screen?

Can I do like this?

sub vcl_recv {
  ....
  log.info(req.http.host); // can i write a log here?
  ....
}

Check if you are asking for `varnishd -Cf file_name` – Tamil Sep 28 '12 at 11:26 — Tamil, Sep 28 '12 at 11:26

score 27 · Accepted Answer · edited Sep 07 '17 at 12:24

27

You can see URL with requested URLs varnishlog utility (it able to write log files)

varnishlog -i RxURL

Example:

import std;

sub vcl_recv {
  ...
  std.syslog(180, "RECV: " + req.http.host + req.url);
  ...
}

edited Sep 07 '17 at 12:24

Yvan

answered Sep 25 '12 at 11:05

ghloogh

VCC-compiler failed:Message from VCC-compiler: Expected an action, 'if', '{' or '}' ('input' Line 49 Pos 9) std.syslog(180, "RECV: " + req.http.host + req.url); – lichengwu Sep 26 '12 at 02:00
Ok, yes, we forgot to import std vmod functions with: `import std;` https://www.varnish-cache.org/docs/3.0/reference/vmod.html – ghloogh Sep 30 '12 at 23:32
Thanks. I can see the log in file /var/log/syslog. – lichengwu Oct 08 '12 at 04:36
Adding comment for later editing: varnish vmod_std 3.0 at https://www.varnish-cache.org/docs/3.0/reference/vmod_std.html#syslog and 4.0 at https://www.varnish-cache.org/docs/4.0/reference/vmod_std.generated.html#void-syslog-int-string-list – Crowie Aug 17 '16 at 13:33

score 17 · Answer 2 · edited Apr 16 '20 at 14:04

Using a vcl config file, import the additional included "standard library", which includes a bunch of utility functions:

import std;

# To 'varnishlog'
std.log("varnish log info:" + req.host);

# To syslog
std.syslog( LOG_USER|LOG_ALERT, "There is serious trouble");

2 Answers2