Stoplight Indicator System Signals When Your Servers Are In Distress


At [mkanoap’s] office, they have a software package that monitors their various servers’ health, but they wanted a separate indicator to display the status of their most critical systems. They put together a simple list of criteria for their display, including the ability to view the status without a computer, and that it share the same red/yellow/green indicators that their monitoring software utilizes. With those needs in mind (and a few hundred dollars to spare), [mkanoap] and crew rushed out to buy a stoplight, then got to building.

Their status system is self-contained, utilizing an Arduino and Ethernet shield to control the stoplight. The Arduino was programmed to act as a web server, and responds to GET requests by toggling any of the three mains-powered lamps using relays. [mkanoap] then created a handful of scripts that check the status of the critical servers every 5 minutes, updating the stoplight accordingly. The whole setup was tucked neatly inside the light’s housing, before being mounted on the wall in their office.

[mkanoap] says that the reaction to the stoplight as been great, though they had to install dimmer bulbs so those people sitting near it were not blinded. His writeup is incredibly detailed should anyone want to construct one of their own, and who wouldn’t?

34 thoughts on “Stoplight Indicator System Signals When Your Servers Are In Distress

    1. It uses a password in the HTTP GET request, which is sent in the clear. A motivated prankster could capture the packets on the same Ethernet segment.

      If security was a concern, I doubt the hardware could run TLS (SSL/HTTPS) but a challenge-handshake scheme could work: The Arduino would respond with a 401 and a nonce (a number that’s different each time and only valid for a short period), which is transformed by the password on the client-side and returned in a second request. The Arduino also does the transformation and if they match, the request is authorized. This scheme doesn’t protect against man-in-the-middle attacks, but it’s a start.

      1. The ability for pranksters to mess with the light was certainly considered which is why it has the rudimentary password protection. But since the light is refreshed on a regular basis by the monitoring system, a casual bit of fooling around by someone who has sniffed the password will set it wrong for 5 minutes at the most.

        If it ever becomes a problem, Kuy’s excellent suggestions would help a lot.

        Of course, this is not part of the formal notification process anyway. It’s mostly for fun, so messing with the light will not let a problem be ignored or anything.

      2. biggest problem i can see, is if the server with the cronjob goes offline, then the light just sticks green

        the arduino should have some kind of timeout, so if it gets no update within 6 minutes, go red automaticaly

  1. I find it funny that while municipal traffic lights are increasingly lit by LEDs, this project, built by a maker/hacker – part of a group which is traditionally obsessed by blinky LEDs – uses incandescent bulbs. I’m sure it’s to maintain the retro authentic look (which it executes superbly.)

    1. Something I’ve noticed is that the new LED traffic lights change too quickly. They’re on, and then they’re off. None of the almost imperceptible fade that goes on with the incandescent traffic lights.

      It makes them feel cold, clinical. I don’t like them.

      1. Agreed. Particularly in an indoor decor environment, the ‘fullness’ created by the combination of incandescent lamp, mirror and glass lens is much more attractive. Besides being almost too bright inside, the led lamps would look more like leds in a traffic light body than a ‘traffic light’ (if that makes any sense).

    2. It’s a good thing he went with incandescent bulbs. The thing about LED modules is that they are BRIGHT. Yes you could dim them with some PWM type setup, but good luck with the lifespan of the LED module. It’s just simpler and cheaper to put in lower wattage bulbs.

  2. I happen to have a stop light in my garage. Ituses the smallest (5watt) bulbs i could find. Worsethan the colored light are the chromatic abberations that are visible due tothe different locatons of the different colorsources.

  3. Damn this reminds me of how I could’ve gotten a big ol traffic light as a kid but I turned it down because I didn’t think I could do anything with it. Now I’m kicking myself for it. Sure, I was like 8 at the time but c’mon, I should’ve had the foresight, it’s only been 23 years!

  4. I don’t get it.

    They’ve gone from specific, detailed, email/sms alerts that fully describes the problem, and the system it’s happening on.

    To a generic, 3-state, summary for their entire data center.

    Seems like a massive step backwards.

  5. 300 bucks for the far out factor of a genuine traffic signal, ouch. Did that come out of the employees pocket, or do they work for a company that understands that an investment in fun, can be good investment? Nice build, and a good job of detailing it.

    1. $300 just for the traffic light. Add $130 for the electronics… damn, that’s expensive :-/

      PS : sorry HaD, I just hit “Report comment” instead of “Reply”… you really should add a confirm function instead of reporting directly.

  6. It only updates every 5 minutes? I think I’d get about 100 calls before I saw a light change to red at my work.

    I see how it’s “neat” and all, but I’d never put that on a wall of mine, it would just look out of place and ugly. It wouldn’t replace e-mail, making it just a showpiece, but I don’t think I’d ever want to show that to anyone..

  7. You nerds (I am a recovering nerd) are taking this out of context. It is NOT some mission-critical aspect of their operation. It is a whimsical, aesthetic aspect of their operation.

    Don’t let technology make you its bitch.

  8. This is how they used to do it in the old days – I worked in telephone exchanges which are full of 54/62-type equipment (some of the stuff they made colossus from) that has red/green bulbs of ever increasing size on the top of each rack, at end of each suite, and on the exterior door of each room. They would also wire up traffic-light sized beacons for other critical status indicators so that all the men in brown coats could see at a glance the status of the network.

    When the text alerts & e-mails are flying it can be helpful to follow the trail of red lights straight to the problem with zero overhead of decoding information.

  9. Cool but couldn’t you make on cheaper and maybe a bit smaller than buying them? Make a box, cut three holes, Use cans or PVC to make the hoods, add leds and some colored film.
    Yes if the company is paying for your time to build it the $300 is probably cheaper but if you are paying for a craft project then make it a craft project.

    1. Oh, it can get LOTs cheaper.

      See the end of step three; you can stop with just three LEDs.

      You don’t even need the colored film, they make LEDs in different colors now. :p

      Seriously though, when brainstorming options we considered a number of home made options; but in the end the thought of a real traffic light seemed cool, it played more to my strengths, and it was after all a funded project.

    1. That’s a cool idea

      You wouldn’t have to change it at all, you would just have to have a script running somewhere that tells it to change.

      Or, you could completely reverse the logic, turning it into a client that looks for a change on the woot web site by re-writing the code (as discussed in the notes) so you don’t even have to have another machine. We only have the test be externally scripted because we wanted to be able to change the criteria without re-flashing the firmware.

  10. dont want to be a troll or anyting but I really dislike this. First there is nothing new here : using indoor old traffic light has done thousands of time. 2/ I wouldnt like to be a customer of that compagny : using such an unrealiable device as an arduino to check very important server is just non sense. arduino is fine for hobbist, to develop etc but not for industrial/ real life 24/24 app. My guess is thoses guys have no knowledge in electronic and so choosed the easiest way.3/ if you use this to monitor you need to use realiable user interfae : leds , not old lights as states previously 4/ the case is way too big for their office: it looks very strange : I hope they dont have customers who visit their office..

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