A tool I'm finding myself using more and more these days is Fabric.

Fabric is a python utility and library for streamlining systems administration tasks on multiple machines.

Although I'm primarily a developer and systems architect, I find that as our company grows I keep getting drawn into sysadmin and devops tasks. We now have quite a number of servers which I need to monitor and manage.

Now, as Larry Wall so profoundly said, one of the great virtues of a programmer is laziness, so if there's a way I can perform the same task on multiple machines without having to manually type out the commands dozens of times, then I'm all for it.

Fabric does precisely that. It's written in Python, and its configuration files are python scripts, so there's no need to learn yet another domain-specific language. I have a file called fabfile.py on my local machine that contains a growing collection of little recipes, and with this I can interact with all the servers in our infrastructure.

So for example, if I want to see at a glance which version of linux I'm running on all my servers, I have a task set up in my fabfile like this:

@parallel
def lsb_release():
    run('lsb_release -a')

When I invoke this via:

$ fab lsb_release

I get a nice little print-out of the current version of all my servers. Fabric runs the task in parallel against every host in the env.hosts variable, which can be set at the command line or in the fabfile.

The following example allows me to see a list of every database running on every database server.

DATABASE_HOST_MACHINES=['dbserver1','dbserver2',...]

@hosts(DATABASE_HOST_MACHINES)
def databases():
    with warn_only():
        run('psql -c "select datname from pg_database;"')

And voila, a call to

$ fab databases

gives me a company-wide view of all our databases.

One further demonstration - this blog itself is generated using Fabric! For details, see the fabfile my Github repository.