TurnKey Linux Virtual Appliance Library

How to debug a broken cron job

I just fixed a broken cron job. It turned out it was a PATH issue. By default cron doesn't have /usr/local stuff in the PATH.

Tips on how to debug cron:

  • change the schedule for the cron job so it runs every minute. It's harder to debug something that happens infrequently.

  • Make sure syslog sends cron logs to /var/log/cron.log. On one of our servers this line was commented out for some reason:

Why use XMPP: native clients vs generic IM alternatives

XMPP, the eXtensible Messaging and Presence Protocol (translation: open IM) rocks. It has a rich feature set. It's well designed. And as a bit of a security nut I especially like that it supports strong encryption and uses a decentralized, federated protocol like e-mail. Anyone can install their own Jabber server (like TurnKey ejabberd). That way private conversations within your domain never leave the security of a server under your direct control. Just like e-mail.

Less is more and the magic number is four

Remember this posts title. It not only rhymes. It's the law!

Sometimes the truth is a bit counterintuitive. Conventional thinking is that more is better. More features. More choices. More options. More is more right?

When we first tried redesigning the Hub's front page we made this mistake. We were so proud of all the big and small features that made the Hub easy to use we listed all of them. As a big wall of text no less. In retrospect I don't know what we were thinking.

My last Perl program - a Perl obfuscater that can eat its own tail

OK, I admit it. I used to program in Perl. And I liked it! My Perl programs were terse. If I could shave a line off, I did. In fact, I spent a non-trivial amount of time figuring the shortest possible programs that solved various problems. Often that meant resorting to various tricks and arcane features of Perl that nobody other than me would bother to understand. I took pride in that.

Python optimization principles and methodology

Methodology

The basic methodology for optimization:

  1. Discover where you program is spending its time (hotspots vs coolspots)

    A good way to get an overview is to use the Python profiler. The Python profile will usually be included in Python's standard library:

4 simple software optimization tips

1) Always be experimenting!

Trying to squeeze out more performance out of your program? Don't be afraid to experiment!

In practice what that means is you setup small, simple throwaway experiments to establish how things work when you're not absolutely sure you fully understand something such (e.g., how many times a second a certain function can be invoked, how the profiler measures blocking IO or the time it takes a sub-program to complete).

How to setup an email to SMS forwarding gateway address with Postfix

SMS is an important tool in the arsenal I use to fight my never-ending war with productivity-destroying distractions.

Colleagues, friends, mailing lists, foes, viagra peddlers and nigerian princes send me in aggregate about 300 pieces of of e-mail every day, most of it not really that important. All of this noise can eat up an enormous amount of my attention so when I really need to concentrate I'm pretty much forced to ignore e-mail altogether for sometimes weeks at a time.

Vim smartopen plugin adds Vim support for CDPATH

Overview

Ever since I discovered CDPATH last year I've been thinking wouldn't it be great if Vim could access files using CDPATH without having to chdir anywhere first. In other words, why can't Vim understand that it has to look for tklbam/restore.py in the CDPATH instead of telling me that it doesn't exist in the current working directory?

Transcend the Drupal documentation, use the source Luke!

During the first few months of my Drupal experience I looked for answers to any issues that came up first in the official documentation, then on Google. It's a big Drupal world out there so more often then not I would find someone had come across exactly the same issue before and I could just parrot the solution without necessarily understanding why it worked.

Pythonic attribute magic (property, customized attribute access)

Many languages encourage programmers to use a getter/setter pattern.

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