DDevelopment & Design

TouK Hackathon – March 2019

Hackathons are prone to fail. It’s because we have very little time to create something useful, actually working and making a wow!-effect.

So this time we wanted to run “THE HACKATHON”, a well-prepared event with a very high success rate. We called it “Ship IT!” to ensure that we will focus on delivering a working product, not only on having fun while making it. We formed an organising team responsible for internal communication, collecting the needs, removing obstacles and buying some snacks and pizza for the event itself.

We thought that if we want to succeed, we’ll have to prepare well. So each team gathered before the event and talked about their plans, the technologies they intend to use and what hardware they need to order. The organizers met with all teams, exchanged details and gave some good advice.

And finally, the day has come! Seven teams started the two-day hacking session at 9AM, continued until 5PM, and showed the demos of all seven projects after 4.30PM on the second day. We gathered 25 participants total.

Here is a quick presentation of the projects we delivered.

Lidar/ROS.org based robot

robot image We always wanted to build a fully autonomous vehicle to transport sandwiches and monitor the Wi-Fi quality over the whole office space. The first step we took was creating a remote controlled platform with Lidar, which allowed to build the office map and made a foundation for future experiments. We reached this goal with ROS.org and mapped a few corridors and rooms in our office at the end of the hackathon. Now we’re almost ready to conquer Mars :D

Quak Liero-like Game

quak team Quak is a PvP platform game inspired by Liero or Soldat. We used a mix of Kotlin, libGDX and box2d (physics) to build a good-looking 2D game in less than 2 days. Destructible level as a mesh of boxes are generated from provided png layers. Additionally, we implemented some extras to diversify the player experience, such as multiple weapons, double jump, blood effects and explosions.

Quiz Game

quiz game DuckQuiz is a game we wanted to use at public event, e.g. conferences. It’s a little bit similar to the legendary Flappy Bird. Your goal is to make the title hero – a duck – go as far as possible! Correct answers give the duck a bump, so the more questions you answer correctly, the further the duck will go. Be careful, though! Three wrong answers will make a brick fall on the duck’s head! To spice things up a little, we decided to introduce a score threshold, which – once achieved – guaranteed a prize. Plus, of course, if you beat the highest score, you will make history as the reigning champion Duck Flyer. The quiz application is written in Kotlin for Android. We used RxJava and Retrofit for communication with the server. For the back-end side, we chose SpringBoot along with Kotlin. There is also a web-based “Hall of Fame” panel and a simple CMS which allows the management of the quiz questions, written in ReactJS.

Own Card Authorization system

demo4 We’re waiting for our private brand new vending machine which we’re going to use for distribution of snacks in Touk. We’ve noticed that we can communicate with it using MDB protocol. We’d like to authenticate in the machine with RFID cards which are commonly used in TouK to open doors. As a first step, we wanted to create authorization system based on RFID cards, but with additional PIN verification part added. Our system should be integrated with internal LDAP. We’ve separated our project into 4 modules: backend (spring boot), web frontend (scalajs-react), mobile app (android) and hardware device (arduino yun). Backend part connects all modules and allows matching RFID cards UID with LDAP logins. Web frontend is designed for users to set and manage their PINs. The mobile app at the moment is dedicated for our administrator to make pairing existing cards with LDAP logins easier. Finally, hardware device was created to read data from card, get PIN from user and check if PIN is correct (via backend). In the next step, we’d like to integrate our system with mentioned vending machine and make payments using it. There is also a plan to enhance mobile app and use it as mobile payment terminal and integrate web UI with Touk SelfCare system.

Notification lights

lights hackers Three suites (3 lights in red, yellow and blue) controlled by Raspberry Pi Zero W communicating with the managing service via MQTT protocol. The service handles messages from Rocket’s (our chat) outgoing web hooks and notifications from GitLab (e.g. opened merge requests).

Team gathering app (e.g. for football matches)

Team gathering app We regularly play football and volleyball after work, but we sometimes struggle with completing the teams. So far, we used a sign-up system based on Confluence pages, which is not mobile-friendly. We also wanted to allow registration for “reserve” players from outside the company. That’s why we built a simple mobile app with a sign-up form, game history and basic player ranking. The app was built with Dart using the Flutter framework and Firebase for storage and authorization.

Internal time reporting API

hr This HR project’s goal was to integrate and simplify the way we log time in our company. We’ve achieved that with a Google Calendar-like GUI and multiple microservices written in TypeScript, Python, Java and Scala!

The Grand Finale

demo1 At the end of “Ship IT!”, the teams had demonstrated the effects of their work. They shared some successes and other stories :) about the used software and hardware and the lessons learned during those two intensive days. The audience were amused when the robot started to explore the room. The Quak team had a bloody battle in their game. The lights were blinking when one of the team members wrote “kanapki” on our internal TouK chat.

demo2 demo3 demo5 demo6

It was very impressive that each team managed to deliver a viable result and show their projects in action. We can’t wait to run the next edition of The TouK Hackahton and hope there will be even more participants and surprising ideas to see.

— Previous article

How we use Kotlin with Exposed at TouK

Next article —

Hacking a robot

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Log4j and MDC in Grails

Log4j provides very useful feature: MDC - mapped diagnostic context. It can be used to store data in context of current thread. It may sound scary a bit but idea is simple.

My post is based on post http://burtbeckwith.com/blog/?p=521 from Burt Beckwith's excellent blog, it's definitely worth checking if you are interested in Grails.

Short background story...


Suppose we want to do logging our brand new shopping system and we want to have in each log customer's shopping basket number. And our system can be used at once by many users who can perform many transactions, actions like adding items and so on. How can we achieve that? Of course we can add basket number in every place where we do some logging but this task would be boring and error-prone. 

Instead of this we can use MDC to store variable with basket number in map. 

In fact MDC can be treated as map of custom values for current thread that can be used by logger. 


How to do that with Grails?


Using MDC with Grails is quite simple. All we need to do is to create our own custom filter which works for given urls and puts our data in MDC.

Filters in Grails are classes in directory grails-app/conf/* which names end with *Filters.groovy postfix. We can create this class manually or use Grails command: 
grails create-filters info.rnowak.App.Basket

In result class named BasketFilters will be created in grails-app/conf/info/rnowak/UberApp.

Initially filter class looks a little bit empty:
class BasketFilters {
    def filters = {
        all(controller:'*', action:'*') {
            before = {

            }
            after = { Map model ->

            }
            afterView = { Exception e ->

            }
        }
    }
}
All we need to do is fill empty closures, modify filter properties and put some data into MDC.

all is the general name of our filter, as class BasketFilters (plural!) can contain many various filters. You can name it whatever you want, for this post let assume it will be named basketFilter. 

Another thing is change of filter parameters. According to official documentation (link) we can customize our filter in many ways. You can specify controller to be filtered, its actions, filtered urls and so on. In our example you can stay with default option where filter is applied to every action of every controller. If you are interested in filtering only some urls, use uri parameter with expression describing desired urls to be filtered.

Three closures that are already defined in template have their function and they are started in these conditions:

  • before - as name says, it is executed before filtered action takes place
  • after - similarly, it is called after the action
  • afterView - called after rendering of the actions view
Ok, so now we know what are these mysterious methods and when they are called. But what can be done within them? In official Grails docs (link again) under section 7.6.3 there is a list of properties that are available to use in filter.

With that knowledge, we can proceed to implementing filter.

Putting something into MDC in filter


What we want to do is quite easy: we want to retrieve basket number from parameters and put it into MDC in our filter:
class BasketFilters {
    def filters = {
        basketFilter(controller:'*', action:'*') {
            before = {
                MDC.put("basketNumber", params.basketNumber ?: "")
            }
            after = { Map model ->
                MDC.remove("basketNumber")
            }
        }
    }
}

We retrieve basket number from Grails params map and then we put in map under specified key ("basketNumber" in this case), which will be later used in logger conversion pattern. It is important to remove custom value after processing of action to avoid leaks.

So we are putting something into MDC. But how make use of it in logs?


We can refer to custom data in MDC in conversion patter using syntax: %X{key}, where key is our key we used in filter to put data, like:
def conversionPattern = "%d{yyyy-MM-dd HH:mm:ss} %-5p %t [%c{1}] %X{basketNumber} - %m%n"


And that's it :) We've put custom data in log4j MDC and successfully used it in logs to display interesting values.