配置Varnish之后如何将网页缓存2分钟。 （Ubuntu 14.04，Apache，PHP）

Question

I have run the below commands and put the source code into /var/www/html directory.

sudo add-apt-repository ppa:ondrej/php5-5.6
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install php5
sudo apt-get install php5-curl
sudo apt-get install apache2
sudo service apache2 restart

I have followed the below link for configuring the Varnish to cache the webpages. But how do i know whether its cached or not. Everytime I open the webpage its showing the same webpage. How to set expiry for it.

I need to cache the webpage for 2 minutes and then expire, so where do I it set those duration.

https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-varnish-with-apache-on-ubuntu-12-04--3

This is what i get when I say

curl -I http://localhost

HTTP/1.1 200 OK
Server: Apache/2.4.18 (Ubuntu)
ETag: "dd6d718cc03aac91085163fd1927f07a-gzip"
Vary: Accept-Encoding
Content-Type: text/html; charset=UTF-8
Date: Wed, 03 Feb 2016 13:17:48 GMT
X-Varnish: 1965452251 1965452250
Age: 13
Via: 1.1 varnish
Connection: keep-alive

Answer 1

You can tell if varnish is caching the page by looking at the HTTP headers returned from the request. The varnish request will have Age: <seconds> appended as a header to tell you the age of the request.

Via: 1.1 varnish-plus-v3
Via: 1.1 varnish-plus-v3
Age: 170

You can tell varnish how long to cache the response (if the proper cache headers aren't set on the response itself) by setting the beresp.ttl value in the configuration file in vcl_backend_response (or vcl_fetch iirc, depending on your varnish version):

set beresp.ttl = 120s;

You can test this by doing

watch HEAD http://localhost:6081

which will repeat the HEAD request to show the headers from the URL every two seconds by default. You'll see Age: increasing until it crosses 120s, when the resource will be returned for the last time and expired from the cache (which means that you can see Age: 122 even if it is set to 120s).

Test it with a value shorter than 120s to see it expire quicker.