robertoduessmann / paralyzed-fetch

How to handle parallel requests (fetch or something else) and wait for the response in Java

paralyzed-fetch

It's a example to how you can run some things in parallel, fetch from an API for example, and wait for the response to return to previously call using ForkJoinPool.

How it works

On ParalyzedFetchWeather we define a new ForkJoinPool, it will be responsable for handle the parallel requests.

When we instantiate the ForkJoinPool without parameters in constructor, it will take from java.lang.Runtime#availableProcessors (if we want, we can also define, like 8 or 16 parallelisms).

private static final ForkJoinPool executorService = new ForkJoinPool();

To call in parallel all requests is only split the collection and for each item call the executor with method submit.

cities.forEach(city -> executorService.submit(() -> weathers.add(getWeather(city))));

Once the call is done, we can use the method awaitQuiescence to the process waits for the finish for all parallels executions before continue.

executorService.awaitQuiescence(TIMEOUT_MINUTES, TimeUnit.MINUTES);

Installation

Build

$ mvn clean install

Running

$ mvn spring-boot:run

Usage

GET /weather/cities

$ curl -X GET http://localhost:8080/weather/cities

License

The MIT License (MIT)