Date/time range lookups on the map

This isn't, technically, a big feature, but I expect it to make a lot of people happy. I should have done it a couple years ago.

The map's user interface for looking up historical tracking data used to only allow fetching a single UTC calendar day at a time. I've now implemented arbitrary date / time range searches, where you can select up to 14 days of track data at a time. It also allows for more exact time lookups, such as 2010-10-20 05:58:00 to 2010-10-20 06:38:00. Click the calendar icon to open up the new search form.

I've also switched to a tabbed view for the year ranges, and brought back a bit of December 2008 data. 2008 will go away over time, but the tabbed view fits at least 3 years without taking an awful lot of valuable screen estate.

The user interface still needs some tuning. The time ranges are expressed in UTC regardless of your time zone settings. The UI doesn't say that yet. It also fails to mention the 14 day limit (but it will complain with a nice red error message box if needed).

I might raise or lower the 14 day limit, depending on the amount and magnitude of server load peaks it generates. We'll see. I'd like to make it 30, but it might have some adverse effects.

I've also made small changes to the real-time map's update API, making the communication between the JavaScript running in the web browser and the server a bit quicker and smaller, saving some bandwidth. This change made it necessary to take the web service into maintenance mode for a few minutes, forcing all current viewers of the map to load the new JavaScript components of the page.

How do you like it? Feedback in the comments, please!

KML overlay support

Tonight I implemented KML overlay support in aprs.fi, which have been requested by some users. You can now place any KML file on top of the real-time map, which opens up a great number of possible applications and mash-ups. The feature is used by adding a 'kml' URL parameter to any real-time map view. Please note that the URL must be encoded properly (/ becomes %2F, : becomes %3A).

For example, here's a simple polygon example made by Google, the Pentagon with a Pentagon-shaped overlay: http://aprs.fi/?lat=38.8720&lng=-77.0570&z=15&kml=http%3A%2F%2Fhe.fi%2Fmisc%2Fpentagon.kml (see the KML file: pentagon.kml)

Here's a KMZ file generated by the Export tool of aprs.fi, stored on another server and overlaid back to aprs.fi: http://aprs.fi/?kml=http%3A%2F%2Fhe.fi%2Fmisc%2Ftest.kmz&lat=60.2326&lng=24.8364&z=12

An external KML file can be used to highlight areas of interest (such as SAR search areas), projecting high-altitude balloon track forecasts, and displaying live data generated by other web services with KML output features. The opportunities should generate lots of fun.

Facebook application: Last call for users

Facebook is dropping support for application tabs on user profiles. Starting from Wednesday this week, users will not be able to add the APRS tab using the aprs.fi APRS application to their FB profile, or publish any other application data in their public profiles. For details, please see the Facebook developers blog.

If you think this is stupid and wrong (like I do), please complain to Facebook. If you are a Facebook user and still wish to try out the APRS FB application and haven't done that before, please do so before Wednesday.

Sorry for the late notice, but I didn't expect them to actually remove it. They promised 4 months of lead time, but now they're pulling the plug after only 1.5 months.

If you ever consider developing a Facebook application, please remember that Facebook can pull the plug for you at any time they wish. It's a gamble, and you can certainly loose the time you've invested in developing a Facebook application.

There is plenty of discussion and complaints about the matter on the FB developers forum

Additionally, if you have any smart ideas on what the APRS application could do (instead of publishing your APRS position to your Facebook friends using your profile tab), please let me know.

Youtube: aprs.fi bookmark feature demonstration

Today I did a little exercise in creating an instructional video. In this Youtube video I demonstrate the new bookmarking feature.

IE7 bookmarks fixed, and help texts translation

The bookmark feature now works on IE7. There was a little bug in there, or maybe it actually is in Microsoft's Internet Explorer 7, since it worked with all other browsers I tried. Workaround implemented.

Additionally, I've finally moved the few help texts which can be opened by the '?' links to templates, so that they can be translated to other languages. This has been requested quite a few times. They're quite long, and I should probably write more of those, which will mean more work for the volunteer translators. Again, a big THANK YOU to all of you – translations are a very valuable contribution and they do help a lot of users to understand the site!

Bookmarking APRS views!

I've just upgraded aprs.fi with a generic view bookmark feature. It allows you to save a real-time map view, together with all of it's settings (tracked callsigns, map type, time range, map center, zoom level...) to a named bookmark, and then recall that same view using the bookmarks (star) button. You can even save a bookmark when tracking multiple stations, or when the "show all" mode is activated while tracking.

Bookmarks are stored together with your aprs.fi user account, so you need to be a registered user and logged in to use this feature. The upside of this is that the bookmarks are shared across all the web browsers and computers you use, as long as you are logged in using the same user account.

The feature is especially handy on mobile devices such as the iPhone and the Androids, because it can be a little tricky to navigate to a specific location or enter a bunch of callsigns on the road.

As a little additional fix, most views now have the primary search input field in focus when the page is opened, so that the searched callsign can be entered without first selecting the input field using the mouse.

Outage on Sunday (502 Bad Gateway)

One of the two aprs.fi web servers got stuck on Sunday afternoon (around 1300 UTC 2010-09-26) and started giving out 502 Bad Gateway responses. About half of the web requests for aprs.fi ended up on the stuck server, so sometimes you got the correct response page and sometimes you didn't. For some reason the automatic failover did not work – in exactly this sort of situation it should magically disable the second server and point all requests to the working one.

I happened to be driving back from the countryside when the problem appeared. After getting home in the evening and analyzing the situation I disconnected the server from the network remotely by shutting down the switch port, so that it would not interfere and that the other web server could handle all of the site visitors. At this point, when the server disappeared completely from the network, the other server automatically took over it's IP address and the service started working perfectly.

The next day, 15 hours after the disconnection, I went to visit the hosting site to bring the server back online, and took a couple of iphone video clips of the servers. First, the primary server (at the moment running the whole aprs.fi site and serving all visitors), and then the secondary server which had just been brought up and was receiving the past 15 hours worth of APRS data from the primary server. It was pretty busy at the time, but it took only an hour to copy over all the missing data from the primary.

After the replay was completed I started up the web service on the second server, too, and the service is now again running in a redundant configuration.

Root cause analysis continues. It was definitely a software glitch, probably something to do with me running a system process under gdb to analyze a SIGSEGV it gets every now and then. It might well have caused some services to freeze. The database didn't hang and continued to replicate until the disconnection, but the web service got stuck and I couldn't log in to the box using ssh, or through the serial console.

I'll also have to fix the health check used to trigger the automatic failover procedure, so that it will work next time this sort of problem appears.

The trip to the computer room gave me an excuse to quickly try out Apple's iMovie for composing a little video. Appears to work, but I guess I still prefer Vegas. There isn't much point in this silly video, but maybe it's interesting for some aprs.fi fans. :)