We use Postgres for a lot of stuff here. Since it's a multi-process database server (unlike MySQL which is multi-threaded), creating a direct connection to Postgres is relatively slow.

This can be worked around by using a connection pool server in front of the DB. Up until recently we used pgpool for this. But it has a few disadvantages:

* It's multi-process itself (although it preforks), so it eats quite a lot of RAM.
* Once you reach the maximum number of processes, it "queues" incoming connections in the OS accept queue, which is ugly.
* It has poor (but improving) instrumentation.

Recently we switched to using PgBouncer from our friends at Skype. It fixes all these problems quite nicely:

* It uses single-process event-based socket handling, using the excellent libevent like memcached. This means it uses several orders of magnitude less RAM than pgpool.
* It has configurable internal queuing, so your clients' connections don't time out if they're in the queue.
* It has good instrumentation in the form of an internal pseudo-database you can query.

Now here are some pretty graphs. Spot where we changed:

Sun 6 May – The Cinematic Orchestra

Here's (most of) the track listing, for those of you with the live CD:

Disc 1:
1. The Awakening of a Woman (Man With a Movie Camera)
2. Child Song (Ma Fleur)
3. As The Stars Fall (Ma Fleur)
4. Familiar Ground (Ma Fleur)
5. Ode to the Big Sea (Motion)

Disc 2:
1. Breathe (Ma Fleur)
2. Man With A Movie Camera (Man With a Movie Camera)
3. To Build A Home (Ma Fleur)
4. Channel 1 Suite (Motion)
5. ?

In the recent (slightly problematic) version of the submissions server, we've added logging of items which are rejected by the spam filter for content reasons. I want to try and use these to evaluate whether we should remove some rules.

Here is a little summary (URLs have been broken by me to stop them profiting off my pagerank and the forums' auto-linking).

Top Rejected Artists:

14633 various artists
6193 various
5662 va
4970 artist
3130 unknown artist
2905 no artist
1287 (+44)
1175 unknown
208 [amatory]
182 various artists dubstep allstars vol. 4 - disc 2 (mixed by dj hatcha)
133 [ingenting]
132 mosaic.wav
122 [game music]
116 v/a
106 (smog)
88 noartist
71 [spunge]
66 [o3]
58 http://spyd3 r.ru/ipbforum
58 elliot goldenthal & various artists
50 [:sitd:]
46 various artists jon brion
45 [soundtrack]
41 (la vela puerca)
32 [www.potencia dance.com]
32 (delerium)
29 [raised fist]
28 various artists - system recordings
28 [unknown]
28 (by dj morphologik)

Top Rejected Tracks:

1742 track 10
1736 track 01
1666 track 02
1632 track 03
1573 (antichrist television blues)
1528 track 11
1507 track 04
1438 track 05
1317 track 06
1311 track 12
1233 track 07
1220 track 08
1138 track 13
1043 track 09
977 track 1
952 track 14
896 track 2
780 track 3
721 track 15
710 track 4
706 track 6
696 track 5
618 track 16
584 track 7
566 audiotrack 01
562 track 8
535 track 9
507 track 17
496 audiotrack 02
494 audiotrack 03

Top tracks (ignoring "Track" and "Audiotrack" filters):

1573 (antichrist television blues)
351 (untitled)
294 (nice dream)
186 (sic)
132 (exchange)
130 (*fin)
120 (intro)
102 bohemian rhapsody.mp3
78 albumwrap album
77 (manifest)
74 (10) and counting
73 (515)
71 (interlude)
68 (c'estlavie; en)
66 (d▒but)
63 (hospital vespers)
61 (letter from home)
58 (intermission)
56 childhood (1)
54 (camel; ch)
52 (hidden track)
44 (unlisted)
43 (12) bother
42 (something)
39 (past due)
33 (a)
31 (hidden finale)
28 (subversive script)
28 (b)
27 (reverse)

Two weeks late for hallowe'en, but here's my latest PHP nightmare. Consider the following two pieces of PHP4 code, from a singleton pattern (apologies for the formatting, I need to fix our BBCode):

A:

function &instance() {
global $httpmanager_instance;
if (!isset($httpmanager_instance)) {
$httpmanager_instance =& new HTTPManager();
}
return $httpmanager_instance;
}


B:

function &instance() {
if (!isset($GLOBALS['httpmanager_instance'])) {
$GLOBALS['httpmanager_instance'] =& new HTTPManager();
}
return $GLOBALS['httpmanager_instance'];
}


They're identical right? Wrong. "global $var" doesn't act the same as "$GLOBALS['var']".

In fact, "global $var" is equivalent to "$var =& $GLOBALS['var']", which means that example A above is equivalent to:

A1:

function &instance() {
$httpmanager_instance =& $GLOBALS['httpmanager_instance'];
if (!isset($httpmanager_instance)) {
$httpmanager_instance =& new HTTPManager();
}
return $httpmanager_instance;
}


Now it should be (more) obvious what is happening. $httpmanager_instance contains a reference, which is getting replaced when you use =& on it, while the actual global variable remains empty. The answer in this case is to use = instead of =&, because in that case, PHP will follow the reference and replace the original variable:

A2:

function &instance() {
global $httpmanager_instance;
if (!isset($httpmanager_instance)) {
$httpmanager_instance = new HTTPManager();
}
return $httpmanager_instance;
}


This is equivalent to B above.

Now I'm not entirely sure what the PHP developers were thinking when they decided to make references and variables appear identical, but they certainly weren't following the Rule of Least Surprise...

But PHP5 fixes all this, right?

The first draft of the long-overdue Audioscrobbler Protocol 1.2 is out. Read more here (comments in that thread, please).

I have one spare ticket to the Bonobo album launch party at The Luminaire in Kilburn tonight (September 26th). I got it for free, so I'm giving it away for free to the first comer.

I've been working on geographic visualisations in my spare time. Here's an animation of the number of scrobbles over a 24-hour period:

Still:



(click for the animation, 4MB animated GIF)

DeviantArt has a new design. I really like it, it's got much better contrast than their old site had, and they've got a nice depth effect going on now. Kind of like what the new Last.fm design did.

I love their JS menus too.

So what do the users think of the new design? It's almost a 50:50 split between love and hate. Kind of like what the new Last.fm design did.

You can't please everyone.