The use of Beanstalkd as a queueing system

What is an asynchronous queue

The classic wikipedia quote (Message queue)

In computer science, message queues and mailboxes are software-engineering components used for interprocess communication, or for inter-thread communication within the same process. They use a queue for messaging – the passing of control or of content. Group communication systems provide similar kinds of functionality.

So one part of a system puts a message into a queue for another part to read from, and then act upon. The asynchronous nature means that each side is otherwise independent from the other, and does not wait for a response. That independence is an important part of the nature of the system though – and we’ll see later how some of the more advanced functionality for our software of choice here can give some extraordinary flexibility to what can be done.

Continue reading "Doing the work elsewhere - Asynchronous Message Queues"

As I mentioned in my second post, ZCE prep – and dumb tests – about open book tests (like Brainbench), having a copy of all the relevant documentation can be incredibly useful, if only from a speed issue. Knowing you can just open a new tab and type a few words to get the information on a function, or concept from the manual takes away so many problems.

I mentioned there that I have a local copy of the main PHP manual – and I wanted to tell you how I keep it, and a couple of other manuals up to date, as well as other documentation.

Continue reading "Always have up to date documentation, part #1"

extending PHP_CodeSniffer by Raphael Stolt shows how to quite easily add to a tool that will report what parts of your PHP source needs a clean-up, from the built in ‘sniffs’ for coding standards, and now adding to that for some slightly more opinionated choices on the maximum number of lines per function, or functions per class.

This could be a start of a whole collection of additional classes for additional checks.

The only challenge I see at the moment (and I don’t think it’s a big one, though I’ve not tried it, so it might not even exist, I’ve just not had the opportunity to look yet) is having to put code into the PEAR directory path, since that is where PHP_CodeSniffer is looking for the base library. I do see that they use long PEAR class-names, so it may just a matter of having the phpcs tool look elsewhere for the base coding style class.

1234.20080102 dev’). After a quick wander around the newly checked out version, maybe run a set of unit tests, just for security, it’s just as easy to put a similar ‘live’ symlink into place with a new link.

If there is ever a problem, rolling back to a previous live version is just as easy. Other configuration changes are made within the code on the apache servername, or the machine’s own hostname (more useful for CLI scripts, generally run from cron).

There are some downsides – with a complete checkout of a 40-some megabyte website (it’s mostly the Zend Framework and other libraries from which I use a number of files, though rarely all), it takes a little while (not too long, it’s a gigabit link between the repository and the main webserver) and there are also some potential caching issues (Etags are usually based on the file inodes), but as we plan to move to a multi-machine cluster – and the images aren’t being served from Apache, but a dedicated image webserver, that’s not a significant issue – and even on Apache we don’t have Etags enabled (Yslow from Yahoo also suggests that).

[edit: 18:06]
Ahah, some investigation – and copious use of echos in the phpcs script, and /usr/share/php/PHP/CodeSniffer.php class:

Creating your own standards, and using them from anywhere on the filesystem – not having to link from inside the PEAR/PHP/CodeSniffer directory:

The coding standard class with your extension:

The class is called PHP_CodeSniffer_Standards_Example_ExampleCodingStandard – the two ‘Example’s being the name of the coding standard. The file is called ‘Example/ExampleCodingStandard.php’



And in the subdir: .../Example/Standards/
– Raphael’s ToManyMethodsSniff.php and MethodLengthSniff.php files “from his post”:http://raphaelstolt.blogspot.com/2008/03/sniffing-refactoring-needs.html

To call it:

I've just read http://www.svn-checkout.co.uk/2008/01/19/how-to-release-new-versions-of-websites/ via http://www.lornajane.net/posts/2008/SVN-Deployment-and-a-New-Site and while I consider revision control an essential tool (my current job is the only one in the last five years where I didn't have to install my own RCS, but in the year I've been here so far, I've added nearly 1000 revisions), I somewhat disagree on the idea they suggest.

That first link, 'how to release new versions of websites', suggests checking out a version of the site as a working copy, (it's certainly something I've done before now), but then it goes on to use the 'svn switch' capability to move between versions (of course, they are also doing in in TortoiseSvn, and there for the live web-server is likely to be running Windows, no way I'd run a server on Windows - not even for testing). There is however some trouble with revision switching - especially on a busy site that has to keep running even while the new version is being put into place. While SVN does atomic commits - the new code goes into the repository all at once, or not, it's harder to do the all at once part on a non-transactional file-system - such as a webserver. The bigger problem is that rolling back will also take time - and in an emergency, the time taken to do something is crucial.

Here's what I do - Whenever I want a new version to go live, which might be from every couple of days to as often as a couple of times per day, I'll update run the script below with the specific revision number to export (and a date/time, but that's just for easy reference). When it runs, it also symlinks the given version as 'dev' - which is part of the path to the site 'dev.example.com', wham, instant new version, and I can trivially delete the symlink and on the same command line symlink the older version (with 'rm dev && ln -s 1234.20080102 dev'). After a quick wander around the newly checked out version, maybe run a set of unit tests, just for security, it's just as easy to put a similar 'live' symlink into place with a new link.

If there is ever a problem, rolling back to a previous live version is just as easy. Other configuration changes are made within the code on the apache servername, or the machine's own hostname (more useful for CLI scripts, generally run from cron).

There are some downsides - with a complete checkout of a 40-some megabyte website (it's mostly the Zend Framework and other libraries from which I use a number of files, though rarely all), it takes a little while (not too long, it's a gigabit link between the repository and the main webserver) and there are also some potential caching issues (Etags are usually based on the file inodes), but as we plan to move to a multi-machine cluster - and the images aren't being served from Apache, but a dedicated image webserver, that's not a significant issue - and even on Apache we don't have Etags enabled (Yslow from Yahoo also suggests that).