Async technique in dropwizard - multithreading

Question

I have created a POST endpoint using DropWizard.
#POST
#Timed
public String runPageSpeed(#RequestParam String request) {
try {
JSONObject requestJSON = new JSONObject(request);
JSONArray urls = requestJSON.getJSONArray("urls");
process(urls); // this takes around 10 minutes to complete
return "done";
} catch (Exception e) {
throw new WebApplicationException("failed", Response.Status.INTERNAL_SERVER_ERROR);
}
}
process(urls); takes around 10 minutes to complete, so if we call this endpoint, it takes more than 10 minutes to get the response.
I want process(urls); to run in the background after receiving the URLs from the request and immediately return a response to the user.
I tried the following code using threads:
#POST
#Timed
public String runPageSpeed(#RequestParam String request) {
try {
JSONObject requestJSON = new JSONObject(request);
JSONArray urls = requestJSON.getJSONArray("urls");
Thread thread = new Thread() {
public void run() {
process(urls); // this takes around 10 minutes to complete
}
};
thread.start();
return "done";
} catch (Exception e) {
throw new WebApplicationException("failed", Response.Status.INTERNAL_SERVER_ERROR);
}
}
This works, but are there any issues if I use this approach, especially at a high volume?

Answer 1

DropWizard users should promote using CompletableFuture for async handling as it is the safest for handling background processing. With CompletableFuture you can move the heavyweight task to a background thread and simultaneously continue with the lightweight task thus can also send back a response to the client.
#POST
#Timed
public String runPageSpeed(#RequestParam String request) {
try {
JSONObject requestJSON = new JSONObject(request);
JSONArray urls = requestJSON.getJSONArray("urls");
CompletableFuture<Void> future = CompletableFuture.runAsync(() -> {
try {
// perform heavyweight task
process(urls); // this takes around 10 minutes to complete
} catch (InterruptedException e) {
e.printStackTrace();
}
});
// perform lightweight task
return "done";
} catch (Exception e) {
throw new WebApplicationException("failed",
Response.Status.INTERNAL_SERVER_ERROR);
}
}
CompletableFuture helps in every aspects whether its using the return value of first complex task into second function or notifying on failure with the vast variety of methods it provides
runAsync()
supplyAsync()
thenApply()
thenAccept()
thenRun()
exceptionally()
handle()
You can also chain the CompletableFuture using thenCompose() and thenCombine() which is used when one task is dependent upon others.