The Edge-case Excuse

I find the excuse that the bug is just for your small “edge case” as an explanation for why it won’t be fixed annoying.

I have found “edge cases” to actually mean we don’t want to fix it. Often the issue isn’t needing some special code to deal with an “edge case” it is the coding was done poorly and breaks in many different “edge cases.” It isn’t that those edge cases need to be coded for. It is that the code should have been written in a robust way that didn’t break for lots of “edge cases” but the excuse given for not fixing the fundamental coding fragility is the bugs found are just “edge cases.”

There are real instances where “edge cases” is a justifiable excuse. For example, adding in special code to deal with some odd category of users that just isn’t worth the cost.

But I just am so tired of fragile coding being excused as if breaking in lots of “edge cases” is perfectly acceptable when the only reason it fails is because the code is fragile instead of being built in a robust way to begin with. The issue isn’t that you have some special edge case that you want special coding for the issue is the code was written in an unnecessarily fragile way that makes it not work unless you follow a list of acceptable use cases.

Code should avoid adding in requirements that are not necessary. The edge case excuse I see used far more due to requirements that the code added which never should have existed instead of actually being an edge case that would require special code. For example, most web pages don’t require javascript (or IE, or flash, or downloading 5 mb of code to view simple text…) to do what should be done (display text, display images…) but some sites code their page to break if javascript… isn’t used by the user. Seeing this as an “edge case” issue missing the point of creating code that has superfluous requirements for the user that create “edge case” failures where they shouldn’t exist but for poor coding practices. In some cases jasvascript is required to do fancy things that are useful, in which case gracefully degrading and potentially not working fully is acceptable.

Related: W. Edwards Deming and Software DevelopmentSoftware Supporting Processes Not the Other Way AroundComplicating SimplicityWhich Prime Minister Said “The last programme I wrote was a Sudoku solver in C++”?

Making Sure You Don’t Run Out of Space on Your VPS

Over the years I have had web sites I work on go down because the server ran out of space (when I wasn’t responsible for the system administration). Well today I had it happen for some sites on one of my servers.

I have a remote monitoring service so I was notified when the sites were unavailable. Looking in the error logs I could see I ran out of space, which is a fairly lame error to make, I think. I cleared up some space quickly and things were in working order again.

A few tips from this experience. To see data on space used and available space from the command line (linux/ubuntu) use the df command.

df

You could check that occasionally to see if anything strange is going on. But it is better to use something like Nagios to monitor the server and provide notice if usage goes past certain points is wise (75%, 80%…).

I found a nice way to find large files (that may be possible to delete to free up space)

sudo find . -mount -ls | awk '{print $7, $11}' | sort -rn > large_file_list

If you get an error with the file creation, you can log in as root (su) or create the file first and then it can overwrite the existing file.

It is smart to have log rotate setup for logs. I didn’t have it setup for every log. To create a file to keep track of all your logs for domains you can do the following. Create a file in the logrotate directory so it is run per your settings.

sudo vim /etc/logrotate.d/virtualhosts

This article from Slicehost provide details on options, a simple setup is to include text such as this in the file created in the line above.

/var/www/domain1.com/logs/*log /var/www/domain2.com/logs/*log {
  rotate 14
  daily
  compress
  delaycompress
  sharedscripts
  postrotate
    /usr/sbin/apache2ctl graceful > /dev/null
  endscript
}

Related: System Monitoring Tools for Ubuntu VPSPhusion Passenger Tips and Troubleshooting IdeasChecklist: Moving WordPress site to a New Host

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