####General info As well-known, Kafka Streams let us use a bunch of Window functions out of the box (see more https://dev.to/frosnerd/window-functions-in-stream-analytics-1m6c).
This small app tries to implement a tumbling window having a fixed length to calculate online statistics for certain amount of time. From tech perspective, it leverages multithreading delegation to ConcurrentHashMap and immutable objects that are thread safe. The map is pre-populated with max-offset capacity + 1 (see a corresponding property in application.yml). All the post requests are accumulated in such a map as per their offset (milliseconds to now, as map keys).
In turn, map values are represented by a specific immutable object. When it comes to collecting multiple post requests with the same offset, a new immutable object is created in order to evaluate analytics correctly. That's where concurrency influences the app making threads wait for the same offset.
While reading data from a map, stale one is filtered so that only the max-offset window can be taken into consideration. The full map scan is performed in parallel processing.
You can also take a look at load test results (http://localhost:8080/report/index.html)
giving an insight into Test and Report informations (load_test.jmx is a Jmeter test).
To try it on your own, just use jmeter -n -t load_test.jmx -l results.jtl -e -o report
provided that you installed Jmeter.
####Requirements to consider before using the app
The project is ought to be built by means of Maven (including the execution
of unit tests): mvn clean install