Archive Page 2

DDoS

Something you have to deal with when operating a website that starts to garner some attention is the DDoS attack (Distributed Denial of Service). The goal of a DDoS attack is to bring the server down and make it unavailable to users. The prevalence of open source software and the reach of the internet make DDoS script toolkits available to anyone who’d like to give them shot.

Who launches these attacks? Thirteen year old kids could be behind the attacks. If your site is extremely profitable – for example, an online gambling site – the DDoS attack could come from organized criminals in Russia seeking to extort money from you. It could even be your hosting provider trying to convince you to upgrade to a more expensive managed service plan :).

MyMetar.com was hit with one of these attacks tonight. The serves have been tweaked to mitigate their impact and firewall rules are being updated. Fun stuff!

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Speed. Hot, nasty speed. Canada too.

Build 20070120 is now in production. This build includes:

  • A 50x performance increase in auto-complete (really, 50x!). Search time has decreased from an average of 1,025 milliseconds (1.025 seconds) to 0.05 milliseconds. Not too shabby.
  • A 15x performance increase for users that have a fair number of stations configured. Competing for first place in the number of stations configured are doublehoya and stevedubs.
  • Cleared Visual flight rules indicators are now shown in the autocomplete window.
  • Canada! The radar library now includes echo top, precipitation, and significant weather imagery from NAV Canada.
  • Preferred radar collection. When registering, user can now select either the United States or Canada for their default radar library and the default imagery for the selected country will appear in their Mosaic Bar.
  • Observations older than two hours are now colored in light grey and have a strike through them.

MyMetar is, as Eleanor Roosevelt so gracefully put it, “all about speed…hot, nasty speed.”

Here is a screen shot of the auto-complete window with Cleared Visual indicators appearing with the results.

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Observations older than two hours old are now shaded in light grey and appear with a strike through the text. This provides a quick visual indicator for observations that you may want to discount as a result of their age.

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Autocomplete!

Last night’s push to production included a couple of new features and a few other minor tweaks here and there. ‘Autocomplete’ functionality is a new feature and will certainly help when you can’t remember the ICAO code for an airport or observation station.

Basically, it works like this: as you type, a snippet of background code communicates what you’ve typed with the server. This code is engaged after you’ve typed two characters. The server then scans through our ICAO station data set looking for matches and presents a list of candidates. The server looks for matches using both the ICAO code and the station name.

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The matches are then merged together and sorted by station code so that you get a nice list of stations to choose from. A couple of pending minor enhancements will really speed up the matching. It’s pretty quick already, but ‘blazing fast’ is the only acceptable outcome! Speed counts when it comes to providing an acceptable user experience.

Shortly, you’ll see the Cleared Visual (200701101705) indicators next to search results which will let you see the flight rules in effect based on the station’s most recent observations.

Also in this minor update is:

  • Support for setting your time zone, which will be used to present observations in local time or zulu time.
  • A user preference for preferred language (yup, foreign translations are coming).
  • A couple of bug fixes for the widgets.

Desktop Widget Update Version 1.2.5

A new version of both the Dashboard and Yahoo! Widget Engine widgets is available. This version adds a pressure trend indicator, MyMetar flight rule icons, and some minor bug fixes – including one that used the first station in a group as the group name in the drop-down.

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Squash, Space, SIGMETs, and Norway

Squash

The IE bug I wrote about earlier was squashed with tonight’s release. The cause: keeping a copy of a new user’s preferences on disk, then replacing those with the default set of preferences created each time the preference set is saved. This only affected new users that signed up after December 16th and only the first time they logged in.

Space: a note about Web Application Development

Developers have a big tradeoff to make when building web (or any, really) applications: time or space. One can choose more available space (RAM memory) or more available time (CPU cycles). You save time by storing more data in memory and gain space by using the CPU to do things like fetch data from a database. If, however, the developer designs the application such that the data footprint is small and the technique for accessing data used reduces CPU time, the result is more bang (more concurrent users and faster page load time) for the buck.

Getting more of both typically means upgrading hardware. MyMetar does a couple of things to get more of both without having to upgrade hardware. Firstly, we store very little information in memory – almost none. This means we can scale to many users without taxing server memory (and wallets). Secondly, we use very efficient storage and caching techniques that minimize the CPU cycles used to fetch and store data. Developers can do some really dangerous stuff with relational databases that turn a very simple task into a slow and lumbering one. Thirdly, we don’t need to store much data about our users (more privacy for you and easier to manage for us). Fourthly, we try to keep the code succinct, which yields great benefits.

SIGMETs

There are a few new images in the radar library that you can now load up on your mosaics bar: surface prognostic charts (current through 48 hour forecasts) and SIGMETs/AIRMETs (turbulence, convective outlook, and “maximum turbulence potential”).

Norway Weather

I looked into adding Norwegian doppler radar imagery to the Library for our Norwegian users. The Meteorologisk Institutt, however, uses a cryptic scheme for generating their radar image URLs – not as developer friendly as the NOAA weather images. Anyone know any propeller heads at Met.no that might want to share their scheme for the benefit of MyMetar users?

They’ve got good looking radar in Norway too. Example:

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Bug: METAR Saving

There is a minor yet annoying bug for newly registered users (new after the 15 December upgrade). Preferences revert to default unless the user first signs out then signs back in. Working on a fix now! This was discovered with Internet Explorer 7.0.

Checkride: Passed!

My PPL “flight test” (a.k.a. check ride) was this morning. Result? Passed!

Since it’s Christmas, it’s only appropriate to quote Clark W Griswald and say “Hallelujah, <censored>, where’s the Tylenol!”.

Passed

The weather section of the oral? No prob ;). He expected I be able to read a METAR, at least. Winds were a bit blustery this morning. Having put the plane down on the centerline on all the landings, though, left me some latitude to forget a few minor details. As the evaluator noted, “if you can put it down in these conditions without running it off the runway, I may overlook some minor omissions.” Should I add a crosswind calculator to MyMetar.com?

Metar

Happy holidays all!


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