Speeding up Symfony with Varnish

##1. Background

The assumptions are following:

• your Digital Ocean droplet LAMP has already been set up
• you know how to open ssh session to your droplet
• Symfony Standard default web page is already available at http://localhost/ within your droplet

If you need additional assistance to meet the above assumptions refer to:

• A tutorial on Installing ssh keys for Digital Ocean droplet
• A tutorial on Running Symfony application on Digital Ocean droplet

##2. Install lynx and visit the default web page

Install lynx:

$ sudo apt-get update -y
$ sudo apt-get install lynx-cur -y

and visit your web site:

$ lynx localhost

If you are using Symfony Standard, you should see the page containing two words:

                    Welcome!
Homepage.

You can quit lynx by pressing Q key on your keyboard.

##3. Install the software to benchmark your site

I will use ab application to benchmark the site. To install it run:

$ sudo apt-get install apache2-utils -y

##4. Run the tests to check current speed of your site

$ ab -c 10 -n 1000 http://localhost/

The result you will get will be similar to:

Concurrency Level:      10
Time taken for tests:   9.432 seconds
Complete requests:      1000
Failed requests:        0
Total transferred:      525000 bytes
HTML transferred:       248000 bytes
Requests per second:    106.03 [#/sec] (mean)
Time per request:       94.316 [ms] (mean)
Time per request:       9.432 [ms] (mean, across all concurrent requests)
Transfer rate:          54.36 [Kbytes/sec] received

Thus, the current speed may be estimated as 100 requests per second.

##5. Install Varnish

$ sudo apt-get install varnish -y

##6. Configure Varnish

Modify the contents of /etc/default/varnish file.

Configure Varnish to respond to queries received on port 8080.

You can achieve this with the following settings:

# File: /etc/default/varnish

DAEMON_OPTS="-a :8080 \
             -T localhost:6082 \
             -f /etc/varnish/default.vcl \
             -s malloc,1024m"

Next modify the contents of /etc/varnish/devault.vcl file.

With the following settings Varnish will use Apache running on port 80:

# File: /etc/varnish/default.vcl

backend default {
    .host = "127.0.0.1";
    .port = "80";
}

##7. Restart varnish

$ sudo service varnish restart

##8. What have we just done?

Right now, your server listens for HTTP requests using two ports:

• 80 - standard port used by Apache
• 8080 - port used by Varnish

When Varnish receives a request for the first time, it contacts Apache to to get the answer. After that, Varnish responds with cached answer.

##9. Run the tests again

This time use port 8080 for tests:

$ ab -c 10 -n 1000 http://localhost:8080/

You should get results similar to the ones shown below:

Concurrency Level:      10
Time taken for tests:   0.165 seconds
Complete requests:      1000
Failed requests:        0
Total transferred:      538000 bytes
HTML transferred:       248000 bytes
Requests per second:    6070.87 [#/sec] (mean)
Time per request:       1.647 [ms] (mean)
Time per request:       0.165 [ms] (mean, across all concurrent requests)
Transfer rate:          3189.58 [Kbytes/sec] received

Now, the speed may be estimated as 6000 requests per second.

The difference is really amazing:

##7. Reading list

1. Apache Benchmark (ab)
2. Piotr Pasich: How to speed up your WordPress 100x in 10 minutes
3. Varnish website
4. Solving the dreaded Varnish 503 error