zapman449 / libvmod-redis

A varnish vmod for sending commands to a Redis server and getting back the response in your VCL files.

vmod_redis

A Varnish module that allows sending commands to redis from the VCL.

This extension is mostly a proof-of-concept; it has only received minimal testing. However, I do run this in production for a heavy traffic website, and except for the expected slowdown when calling Redis, I've had no other issues.

At the very minimum, it will slow down Varnish a fair amount (at least a few milliseconds per request, depending on how fast your network and your redis server are).

So far the module builds and runs on FreeBSD and Linux (tested on CentOS and Ubuntu).

Usage

In your VCL file, include the following line to load the redis module.

import redis;

Functions

redis.init_redis

redis.init_redis(host, port, timeout_ms)

Use the redis server at the given host and port with a timeout of timeout_ms milliseconds. If port is less than or equal to zero, the default port of 6379 is used. If timeout_ms is less than or equal to zero, a default timeout of 200ms is used.

This function is intended to be called from the Varnish subroutine vcl_init. If the call is left out, the module will attempt to connect to the Redis server at 127.0.0.1:6379 with a connect timeout of 200ms.

Example:

redis.init_redis("localhost", 6379, 200);

redis.send

redis.send(command)

Sends the given command to redis; the response will be ignored.

Example:

redis.send("LPUSH client " + client.ip);

redis.call

redis.call(command)

Sends the given command to redis; any response will be returned as a string.

Example:

set req.http.x-redis = redis.call("LTRIM client 0 99");

redis.pipeline

redis.pipeline()

creates a redis pipeline. redis.push(cmd) to push commands. then redis.pop() to retrieve

Example:

redis.pipeline();
redis.push("get your:special:key");
redis.push("incr your:special:counter");
set req.http.special_key = redis.pop();
set req.http.special_counter = redis.pop();

Examples

See the examples/ directory.

Dependencies

• hiredis - minimalistic C client for Redis
• automake
• autoconf

Installation

Step 1. Download Varnish Source

On Ubuntu, this can be easily done using apt-get source varnish. However, you can get the source for Varnish on any OS using Git.

cd /opt
git clone https://github.com/varnish/Varnish-Cache.git varnish
cd varnish
git checkout tags/varnish-3.0.3

Important: You must download the same version of the Varnish source code as you have installed, or you'll get an error when loading the vmod. You can get your current version using varnishd -V.

Step 2. Compile & Install

./autogen.sh
./configure VARNISHSRC=/opt/varnish VMODDIR=/usr/lib/varnish/vmods
make
sudo make install

Be sure to point VARNISHSRC to wherever you downloaded the Varnish source code to.

Important: Some systems such as CentOS 64-bit store vmods in /usr/lib64/varnish/vmods not /usr/lib/varnish/vmods, so change that if needed.

Troubleshooting

Could not load module redis

If you get an error like this when starting Varnish:

Message from VCC-compiler:
Could not load module redis
/usr/lib64/varnish/vmods/libvmod_redis.so
ABI mismatch, expected <Varnish 3.0.4 9f83e8f>, got <Varnish 3.0.5 1a89b1f>
('input' Line 7 Pos 8)

You compiled libvmod-redis against the wrong version of the Varnish source code.