A playground project to experiment with various Hazelcast features.

• CP-susbsystem's fenced locks: to implement singleton tasks.
• IMap with entry listener: to observe specific state changes in the values of a distributed map.
• ITopic pub/sub - To implement topics and expose them via an akka-http web-socket.

Form a local cluster by running 2-3 instances of the app. You can specify a port by supplying it as an argument to the project Main class.

sbt run 9999
//...
sbt run 10000
//...
sbt run 10001

Once the nodes are up, one and only one of them will be holding a lock and populate a distributed map of current weather conditions (keyed by city). One can access to the current weather condition from any node by hitting the following endpoint:

❯ curl localhost:9999/current-weather/athens
CurrentWeather(athens,Sunny,083e3133-1525-43a3-a089-37fae3c4a18d,2020-07-14T14:16:04.025)% 

An EntryUpdatedListener has been configured to react to specific weather condition changes and publish a list of adverts on a distributed topic. One can subscribe to the ads topic by hitting a websocket from any node in the cluster:

[nix-shell:~/code/hatoy]$ websocat ws://localhost:10000/ads
Advert(new-york,Buy this umbrella!)
Advert(barcelona,Buy this umbrella!)
Advert(london,Buy this umbrella!)
Advert(bari,Buy this umbrella!)
Advert(paris,Buy this umbrella!)
Advert(chania,Buy this umbrella!)
Advert(new-york,Buy this umbrella!)
Advert(athens,Buy this umbrella!)
Advert(paris,Buy this umbrella!)
Advert(london,Buy a disposable BBQ!)
Advert(chania,Buy this umbrella!)
Advert(london,Buy this umbrella!)
Advert(bari,Buy this umbrella!)
Advert(london,Buy a disposable BBQ!)
Advert(london,Buy this umbrella!)