RabbitMQ and Erlang and Ubuntu (12.04) Oh My!


As part of an upcoming development effort for a new client, I am looking at using a message broker to facilitate inter-app communications. The use case is that the new system integrates several different data sources into a consolidated view.

For example: When changes are made to the canonical source in postgres, we need to let the our indexer service know that it needs to update the elasticsearch index so the front-end application can serve the freshest data.

The Problem

In 2 words: Unmet Dependencies. Rabbit MQ is built with Erlang. The Erlang packages in Ubuntu 12.04 (Precise) are out of date or not present. I downloaded the RabbitMQ Ubuntu Debian package and expected a quick dpkg -i install. However, instead of a quick list of additional packages that would be installed and a friendly “Y/n?”, I got:

sudo dpkg -i rabbitmq-server_3.2.1-1_all.deb
...stuff...
dpkg: dependency problems prevent configuration of rabbitmq-server:
 rabbitmq-server depends on erlang-nox (>= 1:13.b.3) | esl-erlang; however:
  Package erlang-nox is not installed.
  Package esl-erlang is not installed.
dpkg: error processing rabbitmq-server (--install):
...stuff...
Errors were encountered while processing:
 rabbitmq-server

So. I tried installing Erlang from the Ubuntu packages and got this:

sudo apt-get install erlang-nox esl-erlang
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package esl-erlang is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'esl-erlang' has no installation candidate
Wat do?

The Solution

Go to erlang.org. Find the download page for Ubuntu which is NOT at erlang.org - it is at www.erlang-solutions.com. Craziness. I follow the directions and add this line to my /etc/apt/sources.list

deb http://packages.erlang-solutions.com/debian precise contrib

then

sudo apt-get update

then

sudo apt-get install erlang

then… I still had a problem. The first time I dpkg-ed the rabbitmq-server, it added it to invoke-rc. So when I tried to install erlang, it gave me this:

rabbitmq-server : Depends: erlang-nox (>= 1:13.b.3) but it is not going to be installed or
                        esl-erlang but it is not going to be installed

so to get rid of the invalid package, I

sudo dpkg -r rabbitmq-server

then

sudo apt-get install erlang

Success was in my grasp! However tantilizingly close it may be, however… It still eluded me.

When I tried to install the package again, I got this nasty little message:

sudo dpkg -i rabbitmq-server_3.2.1-1_all.deb
...stuff...
dpkg: dependency problems prevent configuration of rabbitmq-server:
 rabbitmq-server depends on erlang-nox (>= 1:13.b.3) | esl-erlang; however:
  Package erlang-nox is not installed.
  Package esl-erlang is not installed.
dpkg: error processing rabbitmq-server (--install):
 dependency problems - leaving unconfigured
...stuff...
Errors were encountered while processing:
 rabbitmq-server
head banging on desk

so I looked more closely and saw that I could install erlang-nox (which is a package for erlang for stuff that doesn’t require X to be running -get it? “no X”). So I gave it a shot.

sudo apt-get install erlang-nox

It worked.

sudo dpkg -i rabbitmq-server_3.2.1-1_all.deb

And I was finally greeted with this little beauty:

Selecting previously unselected package rabbitmq-server.
...stuff...
 * Starting message broker rabbitmq-server [OK]

Victory was mine.

Success Kid resolves dependencies, neckbeard increaseth

TLDR

download rabbitmq-server debian package from here but DO NOT run it yet.

add this line to your /etc/apt/sources.list (I updated the link below based on an update from Mark J Williams)

deb http://packages.erlang-solutions.com/ubuntu precise contrib

Next, you may need to add the Erlang Solutions public key for apt-secure

wget http://packages.erlang-solutions.com/ubuntu/erlang_solutions.asc
sudo apt-key add erlang_solutions.asc

then

sudo apt-get update

then

sudo apt-get install erlang

then

sudo apt-get install erlang-nox

then

sudo dpkg -i rabbitmq-server_3.2.1-1_all.deb

then have a hot chocolate. You’ve earned it.


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