Comment by dba7dba | Hacker News Reader

Comment by dba7dba | Hacker News Reader

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+1 for Ansible from me.

Of all the tools, I first heard of Puppet first and so I'm assuming it was first on scene? From my limited experience, it seems Puppet is most widely used tool because of that reason. Not necessarily the best of the bunch, but first on the scene. Considering the effort required to roll it out, I am assuming whatever is deployed first will stay as the tool of choice.

I've tried out Puppet, SaltStack, and Ansible, in that order.

What I didn't like about Puppet is that once you deploy a change, the actual change can happen on the "client servers" at any point within next 20 minutes. I may be off on the exact duration but I remember that changes were deployed at any point within that range of time. To me that sounds like not a great idea. What if you want to switch over your web servers at a specific moment? And Puppet requires a dedicated command/control server.

Next I tried SaltStack. I liked it enough. Now that I think about it and hear someone else mention it, yah SaltStack is similar to Ansible. What drove me away from SaltStack was that you essentially need a dedicated command/control server from where all SaltStack commands are sent out to SaltStack "client servers". I did not want to dedicate resource (and money) for a server that is rarely used. And the personal web/lab servers I manage can grow small/large from 2 servers to 10 servers.

Next I tried Ansible. I think Ansible is the perfect choice for me. I only needed to 'devop' just a handful servers and also learn a tool that many businesses seemed to want on resume. So I picked Ansible and it's been great. Some operations are not as flexible as doing it with a shell script (and I assume same issue exists for other tools). But I've had good luck combining Ansible with little bits of shell script to get the result I need.

The best part of Ansible is that any Mac or Linux machine can be used as the "command server", provided that you have the SSH key pair on your Mac or Linux machine.

Lastly, some may not like the ad-hoc way of doing things on Ansible, but I prefer it that way.

I first heard of Puppet first and so I'm assuming it was first on scene?

CFEngine was first, it's based on a kind of maths called "promise theory" and it solved the problem of you had many different kinds of Unix owned by many different groups and had to have a consistent way of saying "all machines belonging to group X need to have user Y and package Z" and it would abstract away the slightly differing syntax between Solaris, SunOS, IRIX, OSF/1, Ultrix, yadda yadda. This is a problem that doesn't really exist anymore.

Chef I think came next, it was written by people who knew Ruby but didn't know maths so they used CFEngine terminology like "converging" but Chef doesn't really do that, it just runs Ruby scripts. If CFEngine was a scalpel, Chef is a mallet. Chef and Puppet are related somehow, same group of devs had a falling out and went their own ways, something like that. They are much of a muchness.

Ansible is cool because it recognises the reality of why CFEngine isn't relevant nowadays: most organisations are running just one particular Linux distro so you can do away with the abstraction and get all the benefits without the complexity.

> it's based on a kind of maths called "promise theory"

Promise theory is not math, despite its name. It doesn't predict anything, it doesn't explain any phenomena. It's an architectural approach. Brilliant, led to a really great software (CFEngine), but it's not "maths".

Basic concepts of promise theory (10 minute video by Mark Burgess who came up with it): https://www.youtube.com/watch?v=2TPsB5WuZgk

2014 introductory article: https://www.linuxjournal.com/content/promise-theory—what-it

Basic book on the subject: https://www.amazon.com/Thinking-Promises-Designing-Systems-C...

It's not "maths" like arithmentic but it's "maths" like graph theory:

Promise Theory, in the context of information science, is a model of voluntary cooperation between individual, autonomous actors or agents who publish their intentions to one another in the form of promises. It is a form of labelled graph theory, describing discrete networks of agents joined by the unilateral promises they make.

https://en.wikipedia.org/wiki/Promise_theory

> It's not "maths" like arithmentic but it's "maths" like graph theory

It's less like graph theory and more like inversion of control: an architecture, not a set of theorems and their proofs. Even Burgess' own book you mentioned is nothing like a mathematical handbook.

I'm a great fan of Mark Burgess and his promise theory, but calling it a mathematical theory or a mathematical domain is simply incorrect.

I hear you.

The book I mentioned (Thinking in Promises) is the introductory-level public book.

https://www.amazon.com/Promise-Theory-Principles-Application... is the heavy-duty scientific stuff.

"In Search of Certainty" (https://www.amazon.com/Search-Certainty-Science-Information-...) is somewhere in-between.

I would say promise theory is its own kind of logic and notation. Thanks for the correction @dozzie.

Actually the sequence was CFEngine, Puppet, Chef.

See http://verticalsysadmin.com/blog/relative-origins-of-cfengin...

> [...] the actual change can happen on the "client servers" at any point within next 20 minutes. [...] What if you want to switch over your web servers at a specific moment?

You don't. Configuration management is a wrong operation mode for a synchronous change. Still, you could order all your Puppet agents to run their scheduled operation now instead of leaving it waiting for its time.

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