This post attempts to explain how to fork child processes in Python, or at least how to use forking on an existing Python script. For some strange reason I’ve had to explain this a few times recently, so I decided an easy to reference blog post would probably make life a little easier.
In managing a group of software engineers, this is something that has happened frequently in my team and has been bothering me for a while. It’s a lot easier for me to notice, as in my case, I actively write software with my team.
On February 3, 1959, Buddy Holly, Richie Valens and JP Richardson (aka The Big Bopper) died in a plane crash. Don McLean immortalized that day as “The Day The Music Died” in his 1971 hit, “American Pie”.
It’s somewhat ironic that on February 3, 2010 the last five /8s from the IANA IPv4 pool have been distributed to the RIRs.
This is the first post of (hopefully) many, detailing some of my Puppet module implementations. Being the first, I thought I would start off with something simple.
This post is thanks to a suggestion from JP Viljoen to check out ferm. Well, I did, and it’s fairly neat. You get to express your firewall configuration in structures resembling simple C code along with using things like arrays, functions and if / else constructs which makes building complex rulesets quite a simple task.
I’ve included an example configuration below of one of my machines. The network configuration is not extremely complex, but there is a mix of IPv4, IPv6 and - as this is an IRC server - some DNAT to make the IRC service available on a number of other privileged ports without having the service actually listen on those ports. This particular server is running Debian however ferm is basically just a front to ip(6)tables so it’ll run pretty much anywhere that runs.
The following python code makes natural sorting sequences of lexical and numerical values a little easier. It supports any iterable containing strings which have embedded numbers. In short it would give you this:
foo1 < foo2 < foo10
instead of this:
foo1 < foo10 < foo2
This post was mostly inspired by this one, which shows how to generate a dependency graph for a MySQL database. Here we do something similar for PostgreSQL.
This script will generate the required digraph data to pipe into graphviz dot which will generate a visual representation of dependencies in a database schema, based on foreign key constraints.
For some reason the OS X install of Git doesn’t include the manpages. Here is how I installed them.
Using C (or C++) to create Python modules is really quite simple, providing you know a little C of course. I recently had to do some work around getting a bunch of legacy C code talking to a newer system and thought I’d post a nice simple example of how the Python extensions work.
This code gives you a single method “do()” that will print the output of a command, passed to it as a string, to stdout and return the exit code as a python int.