Install Varnish on a Raspberry Pi

See also

https://www.varnish-cache.org/docs/trunk/reference/vcl.html#reference-vcl-probes
http://www.weedpi.com/how-to/install-varnish-in-raspberry-pi
Compile & Install: https://www.devolve.net/blog/2013/12/29/probable-compiler-bug-on-raspberry-pi/
Built in subroutines: https://www.varnish-cache.org/docs/trunk/users-guide/vcl-built-in-subs.html
  1. First install checkinstall
$ sudo apt-get install checkinstall
  1. Take the Varnish software from GitHub
$ sudo git clone https://github.com/varnish/Varnish-Cache.git
$ cd Varnish-Cache/
  1. Get some pre-requisites. Don’t worry if you have some of them they wont be reinstalled but if you missed them things may not work as expected.
$ sudo apt-get install autotools-dev autoconf \
  libpcre3-dev libedit-dev libncurses5-dev \
  automake libtool groff-base python-docutils pkg-config
  1. Start the build process – you may not need to run some of these as sudo but its not harmfull to so. This will take about 15 mins
$ sudo sh autogen.sh
$ sudo sh configure CFLAGS="-O1 -pipe"
$ sudo make
$ sudo checkinstall
  1. To make sure your system has an up-to-date linker to point to your correct modules run the following.
$ sudo ldconfig

or:

$ sudo ldconfig -n /usr/local/lib/

6. We need to create dedicated user for varnishd rather than using the default “nobody” user is used for other services

$ sudo useradd varnishd
  1. Create a startup script
sudo nano start-varnish.sh
  1. Copy the following script
#!/bin/sh

ulimit -n 10240
ulimit -l 16384

/usr/local/sbin/varnishd \
-s malloc,256m \
-a 127.0.0.1:8000 \
-f /usr/local/etc/varnish/default.vcl \
-T localhost:6082 \
-u varnishd \
-g varnishd \
-l 8m,1m,+

Health checks

Lets set up a director with two backends and health checks. First let us define the backends (edit the file default.vcl):

backend server1 {
    .host = "server1.example.com";
    .probe = {
        .url = "/";
        .timeout = 1s;
        .interval = 5s;
        .window = 5;
        .threshold = 3;
    }
}

What is new here is the probe. In this example Varnish will check the health of each backend every 5 seconds, timing out after 1 second. Each poll will send a GET request to /. If 3 out of the last 5 polls succeeded the backend is considered healthy, otherwise it will be marked as sick.

Test the health status with:

varnishadm debug.health

File example default.vcl

#
# This is an example VCL file for Varnish.
#
# It does not do anything by default, delegating control to the
# builtin VCL. The builtin VCL is called when there is no explicit
# return statement.
#
# See the VCL chapters in the Users Guide at https://www.varnish-cache.org/docs/
# and http://varnish-cache.org/trac/wiki/VCLExamples for more examples.

# Marker to tell the VCL compiler that this VCL has been adapted to the
# new 4.0 format.
vcl 4.0;

# Default backend definition. Set this to point to your content server.
backend default {
    .host = "emawind.com";
    .port = "80";
    .connect_timeout = 2s; # Wait a maximum of 1s for backend connection (Apache, Nginx, etc...)
    .first_byte_timeout = 60s; # Wait a maximum of 5s for the first byte to come from your backend
    .between_bytes_timeout = 60s; # Wait a maximum of 2s between each bytes sent
    .probe = {
        .url = "/";
        .timeout = 1s;
        .interval = 5s;
        .window = 5;
        .threshold = 3;
    }
}

sub vcl_recv {
    unset req.http.cookie;

    if (req.method == "GET" && req.url == "/varnish-status") {
        return(synth(200, "OK"));
    }

    # Try a cache-lookup
    return (hash);
}

sub vcl_backend_response {
    # Below will cache the page for one week.(1s = 1 sec, 1d = 1 day)
    set beresp.ttl = 1w;
}

sub vcl_backend_error {
    return (retry);
}