The NTP Pool Project is an amazing piece of infrastructure on the Internet. Most people don’t even realize that they are making use of it, but in fact a huge number of Linux distributions (amongst others Fedora, Debian, Red Hat Enterprise Linux, and CentOS) and Internet providers all around the world use the pool to synchronize system clocks in computers, routers and other devices with accurate time information.

The pool is driven by volunteers who invest a little bit of their bandwidth and a tiny little bit of CPU power in running the ntpd software and exposing it to the NTP Pool. When you’ve installed ntpd on a box, you can add its IP address to the pool database. Every once in a while the IP will then be added to the DNS zones for *.pool.ntp.org and devices using the pool will query your server for time information then. The Wikipedia article provides a bit more information about how it works.

I have been running a box in the pool for quite some time now and am pretty satisfied with it: The CPU usage is negligible (ntpd is well optimized in this regard) and other services running on the same box (SMTP, HTTP etc.) consume significantly more bandwidth than what is spent on NTP traffic. And who cares about bandwidth these days?

So: Have some box with a static IP address sitting around somewhere? Go sign up for the NTP pool!

You can even use a box that sits behind a DSL connection, but in this case you should make sure that you really have a static IP address and that your NAT box is capable of handling all the packets coming in and leaving when your machine is in one of the *.pool.ntp.org DNS zones. And if you like playing with exotic hardware, you can probably get your hands on brand-new GPS time hardware provided by Meinberg once you’ve joined.

An incredible number of things on the Internet can be improved. Joining the NTP pool may be a step in the right direction.

I will be spending Monday and Tuesday at Microsoft’s Student Technology Conference.

If things converge towards the worst case, it will be mainly sales pitching with a barbecue plus free beer at night. If things go well, there will be interesting talks, hopefully good discussions and a barbecue plus free beer at night. In any case, there will be a barbecue plus free beer at night, which is a good thing. And the venue seems to be pretty, too.

If you happen to be there as well, I’d be happy if you stopped by and said hello. Unless of course they don’t let me in with a MacBook Pro in my bag …

There is a nifty example by Rasmus Lerdorf about using file upload hooks in PHP 5.2.x to generate a progress bar while uploading a file through a HTML form. The source code is pretty self-explaining regarding all the things that happen on the client side, but unfortunately Rasmus does not mention what is required on the server side to make the magic work.

In order to make it possible for clients to regularly poll a server for the progress of an upload, one needs a bit of middleware that hooks into the right places inside PHP and exports the progress information to “userland” PHP code. In Rasmus’ case, he is using the APC opcode cache to do this. Recent versions of it come with a (yet undocumented) feature which, once enabled, listens for incoming file upload requests that contain a special field called APC_UPLOAD_PROGRESS. If this field is given, APC creates a cache entry named after the value of the field and regularly populates the file upload progress to this entry.

If you look closely at Rasmus’ example, you’ll notice that not only the script uses apc_fetch() in order to read information from a shared memory segment, but also that it includes the magic APC_UPLOAD_PROGRESS field. The value of the field is generated using the uniqid() function so that multiple file uploads happening at the same don’t use the same cache entry.

So how does one trick APC into working that way? The documentation does not say a word about it at the time of writing this, but the installation instructions in the CVS repository tell us that one needs to add apc.rfc1867 = 1 to php.ini in order to enable the hooking. Once you know that, everything works just magically.

Hope this helps.

Apparently the readership of my small niche of the web has no interest in GPS at all, because I received zero replies after my recent inquiry. Oh well, I don’t mind, really.

So today I went on a GPS unit foray with the intent of getting an eTrex Summit, which costs about EUR 220 in Germany, but came back home with something significantly better for a smaller price:

At their fantastic Cologne store Globetrotter is currently selling out their stock of eTrex Vista units which normally cost EUR 429 for EUR 199, because apparently Garmin is about to release a new model or something like that in the next weeks. This means that one gets the Vista unit which has all features of Summit plus basemap support (which I don’t really, but this doesn’t matter) for 20 bucks less. Pretty cool price. Pretty cool toy.

Today I threw my name in the hat for the upcoming PEAR Group election. I have been thinking about whether to run for another legislature or not (I am a member of the current Group) ever since it became apparent that there is interest in the PEAR developers community to form a new organizational structure for the project. In the end I decided in favor of a candidature because I couldn’t come up with a really good reason why I should stop my involvement. A few months ago I would have most likely decided differently for various reasons, but these days the PEAR Threat Level is back to green for me.

Now let’s see what the outcome of the election will be. In any case it will be good for PEAR, which is important. If I don’t get enough votes, there is always CPAN. Or the Cheese Shop. Or raising sheep.