Nonlocality

Three years ago, I was porting a Perl CGI-based system to FastCGI, one URL at a time, using mod_rewrite to do the dispatching.  (If the handler.pm exists where the FCGI dispatcher will look for it, invoke this request via FastCGI.)  A consequence of this is that the core library code needs to run on both paradigms, since both front-ends use it.  That runs straight into problems when the CGI access checking functions blithely print and call exit when the access is denied.

Instead of updating 60+ scripts to read e.g. $session = get_session() or Site::CGI->go_login; I decided to get hackier.

rumprun php7 experiment results

I forked rumprun-packages to build its php7 package with more features by default.  The original says it’s an “unmodified PHP 7.0.3” build, but it uses --disable-all to build with a minimal number of extensions by default, and that’s not really great for showing just what could work on rumprun.

I made a “mega” build which contains everything I can possibly include into it, including packaging up libjpeg-turbo and libpng so that this PHP can use gd.

I have been unable to get the memcached extension to work, though.  libmemcached-1.0 is written in C++ and depends on some exception-handling symbols.  PHP links with $(CC), which doesn’t include any C++ support.

I’d probably be more disappointed in this, except that I don’t know if rumprun PHP is all that useful.  Options are the single-threaded CLI HTTP server (not intended for production), or using ye olde php-cgi SAPI… which is also not a multithreaded option.  It expects to run single-threaded child processes under a FastCGI process manager.  (php-fpm simply integrates a process manager, so that you don’t need to find a separate one and integrate it; it’s also multi-process.)

And rumprun doesn’t have processes.  It’s a unikernel.

Scaling

How it feels when we try to procure stuff. Maybe we’re just a personal sized business?

This is only getting worse, as each AWS hardware generation raises the machine size floor.

My Blogger Pipeline

For the past couple of years, I’ve been uncomfortable with the notion of Google watching my every thought as I type into a draft on the Blogger site. (Since a post whose working title was “VPNs are hard,” apparently.)

As a coder, everything can be solved with the code-hammer, so I wrote 7 KB of PHP. Now, I can write locally in Markdown, then run markup-menu.php.  This is a stupidly simple program that takes a unique filename prefix, finds the matching *.md file, and passes it to the much larger markup.php.

That program takes a file, preprocesses the Markdown a bit for compatibility with Blogger’s “preserve line breaks” setting, and post-processes the resulting HTML to iron out a few more quirks.  That file can be copypasta’d into Blogger.

Once there, it gets Blogger dressing like tags, then I click Preview.  If nothing’s wrong, it gets posted, as if it sprang fully formed from my head into Blogger.

Modern AJAX in jQuery

In the dark ages, I wrote my own wrappers for jQuery.getJSON because it had the function signature:

$.getJSON(url [, data] [, success])

And I wanted to provide an error handler.  So, our corporate library (represented by LIB) has a function like:

LIB.getJSON(url, data, success [, error])

I also didn’t know if I could rely on getting a response body from error events, so where possible, errors are returned as 200 OK {Error:true,ErrorMsg:"boom"} and the LIB.getJSON catches these and invokes the error callback instead of the success one.

(One more sub-optimal design choice: like, almost the whole point of LIB.getJSON is to pass an error handler and let the user know “okay. we are not loading anymore.”  But notice that the error handler is still considered optional for some reason.)

If I were designing this from scratch today, the service would return errors as HTTP error responses, and I’d use the “new” (added in 1.5, after I started jQuery’ing) Deferred methods.

function success (data, txt, xhr) {
    // ...
}
function error (xhr, txt, err) {
    var r;
    try {
        r = $.parseJSON(xhr.responseText);
    } catch (e) {}
    // ...
}
$.getJSON(url, data)
    .then(success, error);

Result: a more RESTful design, with less glue.

I’d probably still have an “error adapter generator” function which converts all the possibilities for xhr/txt/err down to a single message string, and pass newErrorHandler(showErrorUI) as the error callback into .then().  But the point is, there’s no need to have LIB.getJSON as a whole anymore, to both accept an error callback and filter ‘successfully returned error’ values.

Ten Years of Inheritance (in professional coding)

I wrote in another draft:

And fundamentally, inheritance is the wrong tool for reuse.  Providing lots of small methods to make for improved reuse through inheritance is an equally wrong approach.

I wanted to write about that a little more.

Cases where inheritance has worked out well: when I can arrange for a base class to provide a lot of functionality, and one or maybe two abstract methods overridden in the subclass.  Essentially, this comes down to “using inheritance as a mechanism to implement a strategy for some small, but critical, polymorphic bit.”  Or perhaps, “making a DSL by providing operations in a base class, then implementations in child classes.”

Probably the most accessible example of this is PHP’s FilterIterator which does little more than wrap a regular Iterator with an accept() method.

Notably, it doesn’t extend anything itself to do this.  It composes another iterator and exposes that through the OuterIterator interface.

Perl Retrospective

Perl was the first language I really did serious work in.  To this day, even though it’s dying, I still like it.  It’s different, which is at once both its major virtue, and its Achilles heel in the modern programming landscape.

Let’s talk about what makes Perl Perlish, startng with the good parts.

(Note that I use a lot of 5.10 features like say and maybe the // operator.  For the most part, assume a use v5.10; line before any code. I may not adhere to use strict; use warnings; in this post, but my production code does.)