Hank Beaver » varnish

Testing Varnish VCL Syntax

hbeaver — Mon, 02 Nov 2009 18:15:00 +0000

The simplest way to test syntax is to use the administration console via telnet on a Dev/QA Varnish machine. Your current running Varnish should allow your IP/localhost to connect if you have implemented a Varnish ACL.

Start up Varnish with single command-line
Login to console via telnet
Load the config you wish to test
Use the config.

On OSX:

sudo /usr/local/sbin/varnishd -F  -a localhost:3000 -b localhost:6081 -T localhost:6082

From another console/shell/ open connection to Varnish management console:

telnet localhost 6082
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.

Load config and try to use (the config used in this example has a syntax problem. Therefore, you will see compilation errors:

vcl.load error /Users/hbeaver/code/varnish_demo/config/syntax_error.vcl
106 181
Message from VCC-compiler:
Expected one of
	'acl', 'sub', 'backend',  or 'director'
Found: '}' at
(input Line 12 Pos 1)
}
#
Running VCC-compiler failed, exit 1VCL compilation failed

Conversely, if the VCL has good syntax you should see no errors:

vcl.load good_config /Users/hbeaver/code/varnish_demo/config/default.vcl
200 13
VCL compiled.

Varnish cache purge Rake task

hbeaver — Thu, 16 Jul 2009 02:28:24 +0000

This example uses Ruby to telnet into Varnish and issue the “url.purge .*” command. The only gotcha is that the varnish telnet server does not issue a command prompt which causes Ruby telnet to timeout and get cranky. Well a little exception handling hacks past this. Enjoy.

require 'rubygems'

namespace "varnish" do

  desc "Purge ALL urls from Varnish"
  task :global_purge => :environment do

    #It WILL timeout, just accept it. Varnish does not have a command prompt.
    require 'net/telnet'
    @result = ""
    begin
      localhost = Net::Telnet::new("Host" => "localhost",
      "Port" => 6082,
      "Timeout" => 5)
      localhost.cmd("url.purge .*") { |c| @result = c}
    rescue Exception
      if @result.include? ("200 0")
        puts "varnish purged OK."
      else
        raise "Varnish not purged."
      end
    end
  end

end

Reminder to self and world: Varnish uses POSIX regex.

hbeaver — Tue, 14 Jul 2009 19:26:45 +0000

What does this mean? Well for starters, those nice little PCRE shorthands for character classes just don’t work! So putting this in your Varnish VCL will silently do nothing:

if (req.url ~ "/\d+(/$|/\?|\?|$)") ...

whereas this match:

if (req.url ~ "/[0-9]+(/$|/\?|\?|$)") ...

Enjoy.