S3 static site with SSL

s3-static-site

S3 static site with SSL and automatic deploys using Travis” is a goldmine of all those simple technologies tied into a single knot for an impressive result.  It has a bit of everything:

  • Jekyll – simple, blog-aware, static sites engine, for managing content.
  • GitHub – for version control of the site’s content and for triggering the deployment chain.
  • Travis CI – for testing changes, building and deploying a new version.
  • Amazon S3 – simple, cheap, web-enabled storage of static content.
  • Amazon CloudFront – simple, cheap, geographically-distributed content delivery network (CDN).
  • Amazon Route 53 – simple and cheap DNS hosting and domain management.
  • Amazon IAM – identity and access management for the Amazon Web Services (AWS).
  • Let’s Encrypt – free SSL/TLS certificate provider.

When put altogether, these bits allow one to have a fast (static content combined with HTTP 2 and top-level networking) and cheap (Jekyll, GitHub, Travis and Let’s Encrypt are free, with the rest of the services costing a few cents here and there) static website, with SSL and HTTP 2.

This is a classic example of how accessible and available is modern technology, if (and only if) you know what you are doing.

runkit – changing the PHP internals on the fly

Here is something I didn’t know about until today – PHP’s runkit extension:

The runkit extension provides means to modify constants, user-defined functions, and user-defined classes. It also provides for custom superglobal variables and embeddable sub-interpreters via sandboxing.

This blog post – “Shimming PHP for Fun and Profit” – demonstrates how to use it with a case for a custom base64_decode() and unserialize() functions.  Here is the actual code on GitHub, which shows off how to use runkit_function_rename() and runkit_function_add().

This is not something one would use frequently, but might be an absolute life saver on a rainy day.

Deployer — Deployment tool for PHP

deployer

Deployer is yet another tool for deploying PHP projects.   It looks to have more similarities with Laravel Envoy and phake, than with Robo.li, of which I am a new and growing fan.  But I thought I’d throw it into the mix here, just in case I’ll change my mind in the future.

Top 29 books on Amazon from Hacker News comments

hacker-news-books

I came across this nice visualization of “Top 29 books ranked by unique users linking to Amazon in Hacker News comments“.

Amazon product links were extracted and counted from 8.3M comments posted on Hacker News from Oct 2006 to Oct 2015.

Most of these are, not surprisingly, on programming and design.  A few are on startups and business.  Some are on how to have a good life.  Which is a bit weird.

Chrome Extension : var_masterpiece – turn PHP var_dump() into a thing of beauty

var_masterpiece

Var Masterpiece is a Google Chrome add-on, which formats PHP var_dump() output into something much more beautiful and useful.  You can customize the type colors and a few other things in the extension options, once installed.

SmartDraw – The Smartest Way to Draw Anything

It’s not often that I need to draw a diagram or a flowchart these days.  My time is mostly consumed by more technically challenging tasks.  And whenever I do have to produce some form of a chart, I usually fallback on to the Graphviz dot, which allows me to do something in literally seconds.

basic-flowchart

However, I’m pretty sure the day will (or, rather, return) when I’d need a tool to produce eye-pleasing diagrams and flowcharts.  For that day, and for that day only, I’m leaving the link to SmartDraw here.  It’s a commercial offering, but at $15/month for their cloud-hosted web-based application, it’s seems to be quite a bargain.

devices-cloud-buy

Quick way to create a PHP stdClass

Simon Holywell shows how to quickly create the stdClass in PHP and populate it with properties and values, by casting an array to an object:

$x = (object) [
    'a' => 'test',
    'b' => 'test2',
    'c' => 'test3'
];
var_dump($x);

/*
object(stdClass)#1 (3) {
  ["a"]=>
  string(4) "test"
  ["b"]=>
  string(5) "test2"
  ["c"]=>
  string(5) "test3"
}
*/

A couple of things to keep in mind here are:

  1. In PHP, an associative array key have multiple same keys.  If you cast such an associative array to object, the latest key will silently overwrite the value of the previous ones.
  2. The order of properties in the object will not necessarily match the order of keys in the associative array.

Very handy!

SQL Server in a Fedora Docker Container

MS SQL Server and Docker

It’s a well known fact that I am not the greatest fan of Microsoft and their technologies.  I’ve been bitten many a time through the years.  And not even them becoming a Platinum Partner in the Linux Foundation can change my attitude towards them.  It’s just been too much pain, and scars, and tears, and sweat.

But the way life is, once in a while, I just have to work with or around them.  Recently, for example, at work, we’ve done a project that just had to use MS SQL Server and there was no way to get around it.  Gladly, I managed to find just the right image on the Amazon AWS Marketplace, and spin a new EC2 instance for testing.  The local development was difficult, but at least we had a place to test stuff before sending it off to the customer.

If such a need arises in the future, I think I’ll give the MS SQL for Linux a try.  And that’s when this article from Fedora Magazine might come in handy.  MS SQL + Docker + Fedora.  Hmm.

Dependency resolution with graphs in PHP

One of the projects I am working on at work presented an interesting problem.  I had a list of items with dependencies on one another and I needed to figure out the order in which to use those items, based on their dependencies.

For the sake of the example, think of a list of database tables, which reference each other.  I need a way to export those tables in such a way, that when imported back in, tables that have dependencies will be imported after all those tables on which they depend.  (It’s not the real task I’m working on, but close enough.)

Consider the following list as an example of input data:

// List of items with dependencies.  Order is not important
$tables = [ 
    'articles_meta' => ['articles'],
    'articles' => ['users', 'categories', 'tags'],
    'categories' => [],
    'comments' => ['users', 'articles'],
    'options' => [],
    'tags' => [],
    'users' => [],
    'users_meta' => ['users'],
];

The result of the dependency resolution should give me the list like this (there are variations in order, of course, as long as the dependencies are satisfied):

categories
options
tags
users
users_meta
articles
articles_meta
comments

There are several ways to solve this problem.  My first attempt took about 50 lines of code and worked fine, but it lacked elegance.  It had too many nested loops and tricky conditions and was difficult to read.  My second attempt was slightly better, with a bit of a recursion, but still looked somewhat off.  It felt like there is a better way to do it, and that I’ve done something similar before, but I could put my finger on it.

I thought I’d take a look at something that solves a similar problem.  Composer, PHP package and dependency manager, surely had something to offer.  A brief check of the GitHub repository, and that idea is out of my hand.  Composer deals with much more complex issues, so its Dependency Resolver code is not something I can grasp in a few minutes.

It was time for some Googling.  Moments later, my deja vu feeling of “I’ve seen this before” was easily explained.  This problem fits into the graph theory, which I probably used last back in my college years.  Of course, I could have grabbed the book off the shelf and refresh my knowledge, practicing the sacred art of the Real Programming.  But time was an issue, so I cheated.

I found this “Dependency resolving algorithm” blog post by Ferry Boender over at Electric Monk (thanks man!).  He had exactly what I needed – simple and straight forward recursive algorithm for walking the graph, circular dependency detection, and even some performance optimization.

dep_graph1

The only problem was that his code is all in Python.  But that’s not really a problem.  So I’ve rewritten his code in PHP and got exactly what I needed.  Here it is:

// List of items with dependencies.  Order is not important
$tables = [
    'articles_meta' => ['articles'],
    'articles' => ['users', 'categories', 'tags'],
    'categories' => [],
    'comments' => ['users', 'articles'],
    'options' => [],
    'tags' => [],
    'users' => [],
    'users_meta' => ['users'],
];

$resolved = []; 
$unresolved = []; 
// Resolve dependencies for each table
foreach (array_keys($tables) as $table) {
    try {
        list ($resolved, $unresolved) = dep_resolve($table, $tables, $resolved, $unresolved);
    } catch (\Exception $e) {
        die("Oops! " . $e->getMessage());
    }   
}

// Print out result
foreach ($resolved as $table) {
    $deps = empty($tables[$table]) ? 'none' : join(',', $tables[$table]);
    print "$table (deps: $deps)\n";
}

/**
 * Recursive dependency resolution
 * 
 * @param string $item Item to resolve dependencies for
 * @param array $items List of all items with dependencies
 * @param array $resolved List of resolved items
 * @param array $unresolved List of unresolved items
 * @return array
 */
function dep_resolve($item, array $items, array $resolved, array $unresolved) {
    array_push($unresolved, $item);
    foreach ($items[$item] as $dep) {
        if (!in_array($dep, $resolved)) {
            if (!in_array($dep, $unresolved)) {
                array_push($unresolved, $dep);
                list($resolved, $unresolved) = dep_resolve($dep, $items, $resolved, $unresolved);
            } else {
                throw new \RuntimeException("Circular dependency: $item -> $dep");
            }
        }
    }
    // Add $item to $resolved if it's not already there
    if (!in_array($item, $resolved)) {
        array_push($resolved, $item);
    }
    // Remove all occurrences of $item in $unresolved
    while (($index = array_search($item, $unresolved)) !== false) {
        unset($unresolved[$index]);
    }

    return [$resolved, $unresolved];
}

Running the above code produces the following result:

$ php dependecy.php 
users (deps: none)
categories (deps: none)
tags (deps: none)
articles (deps: users,categories,tags)
articles_meta (deps: articles)
comments (deps: users,articles)
options (deps: none)
users_meta (deps: users)

Which is exactly what I was looking for.  And now that I have it here, I’ll probably be needing it again and again.  It’s an elegant hammer to a lot of my nails.