John Kawakami's blog

Blog comment response about burrito survey.

I was reading an old blog post, and found an annoying comment, and responded at length with some info which i've learned in the past decade or so.

http://www.greattacohunt.com/2010/11/top-10-bean-and-cheese-burritos-in-la.html#comment-form

John 2/3/14, 2:03 PM

Django, forcing a specific migration

Migrations are awesome magic, until the magic fails. Then it's an awesomely frightening engine of change that threatens to wipe out your entire database.

So, before doing what I say, backup your database.

I had to enforce a "unique=True" constraint on a model. Migrations are supposed to automatically create a constraint in SQL, as well as its implied index. A quick look at the indexes (SHOW INDEXES FROM Model) didn't show the index.

Battle of the Naming Conventions (how to avoid them in Django REST Framework)

Python and Django like snake_case.

AngularJS feels like Java, and likes camelCase.

HTML likes dashed-words.

MySQL docs like snake_case, but I see more PascalCase used in databases. It's case-sensitive, too.

Parse.com uses PascalCase for tables/classes, and camelCase for columns/properties/fields. That's like Java OOP.

Django likes to append _id to your primary keys.

So... the problems start to happen when one piece of named data is passed from one layer of the system to another. It's just a good policy to use the same names at all layers, if possible.

Buttons vs. Links, and how to make buttons that look like links, and act like links, but aren't links.

This is a common UI element that hovers between "pattern" and "anti-pattern", but it's one I've seen in Drupal, WordPress, and a few other places. It's the button next to a link, where the link acts just like a button:

Technically, it's a violation of UI principles, to have a link that does something to the server's state. Anthony at uxmovement thinks so, but I disagree with him, because the way the link is next to the button, it's obvious that it complements the button.

File Sync and Share and File Server Terminology Clashes

I was thinking about file sync issues, and realized there are some problems discussing or describing problems, because the terms "share" and "open" mean different things in different situations.

Some applications share data by opening a file in a shared folder on the server. They are all working in the same file, and the server's operating system mediates the process.

No Wonder My PulseAudio Stopped Working

The microphone stopped working on my computer. Based on my reading, the problem, I think, is that I'm using an older motherboard from around 2010s, an add-on card that does TV, and Ubuntu with PulseAudio. The mic input on the sound card just stopped appearing in PulseAudio.

It's still visible in ALSA.

A Django REST Framework Technique for more Detailed Related Records

This is a nice way to deal with building lists of objects to display in tables. It's kind of hidden in there, but in your serializer, you can specify that a field is represented by another serializer.

The result is a list of objects instead of a list of URLs or PKs.

Now, going with that, you can save on data transfer by serializing only a few fields.

Intermittent Django REST Framework glitch examined with Apache Benchmark

While programming in the rest framework, I hit this error, intermittently, but over and over, along with others:

Could not resolve URL for hyperlinked relationship using view name "parseuser-detail". You may have failed to include the related model in your API, or incorrectly configured the `lookup_field` attribute on this field.

Being a noob, I hit the books (documentation) again, and again, and thought I had it right, or close. (Don't start out creating Django models for non-Django-managed tables. It's pretty hard. It's better to learn the vanilla Django way first, if possible.)

Instant Cross-Domain Access for Everyone with CORS in PHP

Here's a snippet of code that will make your PHP REST API work cross-domain, through the magic of CORS:

/**
 * CORS is a way to allow scripts from other domains to post to this URL.
 */
if ($_SERVER['REQUEST_METHOD']=='OPTIONS') {
    header('Access-Control-Allow-Origin: *');
    header('Access-Control-Allow-Methods: POST, OPTIONS');
    header('Access-Control-Allow-Headers: Content-Type');
    exit();
}
header('Access-Control-Allow-Origin: *');

Django Rest Tutorial, Inverted

[I hesitate to post this, because it makes me look like I'm a slow learner... but, oh well. I hope someone finds this interesting.]

North Carolina Judge Expands definition of "Computer Professional" to Include Admins

North Carolina Judge Upholds Employer Classification of Employee as Exempt Computer Professional

This is a big loss for net admins. The exemption was intended for programmers (and even that might be considered a loss).

How to SSH Tunnel to a Remote MySQL Server with Python

A demo of how to incorporate SSH tunnels into a Python system administration script.

Like all sysadmins, I write scripts to automate routine operations. Lately, though, I have needed to write scripts that automate routine operations on a remote system, and we need the security barriers to be a little higher than in the "old days".

We're accessing our database through an SSH tunnel, rather than via a regular encrypted socket. (The SSH connection will eventually require key pairs, and disallow regular passwords.)

WSGI, PSGI, Rack - learning some new backend stuff

(This is one of those articles I sometimes fear writing, because it reveals a vast gap in my knowledge. I've spend most of the past decade in PHP programming, with numerous forays into other langauges and frameworks, but mostly in the app dev end. I have to deploy my code and that's made me take forays lower into the stack.)

Python str.split, annoying design.

Even after a year of diddling, I'm still a python newb, and things like str.split(None) are why.

Everyone knows split splits strings on a character (or in the civilized world, a regex). str.split(None) splits on whitespace and then trims leading and trailing whitespace. It's a great feature, but why not call it str.split_whitespace?

'a b'.split(None) returns ['a','b'].

'a,,,b'.split(',') does not return ['a','b']. It returns ['a','','','b'].

Security Logic Simplified into a Cheatsheet

Came up with this comment to help me think through end-user security.

~~~~ /* * Security logic is based roughly on NTFS style allow and deny. * * The logic is as follows, in order: * 1. If a specific role or user is in the deny list, they are denied. * 2. If a specific role or user is in the allow list, they are allowed. * 3. Otherwise, they are denied. * * There are three special values.

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