How to optimize Tomcat for Feed pull

Question

We have a mobile app which presents feed to users. The feed REST API is implemented on tomcat, which parallel makes calls to different data sources such as Couchbase, MYSQL to present the content. The simple code is given below:

Future<List<CardDTO>> pnrFuture = null;
Future<List<CardDTO>> newsFuture = null;

ExecutionContext ec = ExecutionContexts.fromExecutorService(executor);

final List<CardDTO> combinedDTOs = new ArrayList<CardDTO>();

// Array list of futures 
List<Future<List<CardDTO>>> futures = new ArrayList<Future<List<CardDTO>>>();

futures.add(future(new PNRFuture(pnrService, userId), ec)); 
futures.add(future(new NewsFuture(newsService, userId), ec)); 
futures.add(future(new SettingsFuture(userPreferenceManager, userId), ec)); 

Future<Iterable<List<CardDTO>>> futuresSequence = sequence(futures, ec); 

// combine the cards 
Future<List<CardDTO>> futureSum =  futuresSequence.map( 
        new Mapper<Iterable<List<CardDTO>>, List<CardDTO>>() {
            @Override 
            public List<CardDTO> apply(Iterable<List<CardDTO>> allDTOs) { 
                for (List<CardDTO> cardDTOs : allDTOs) {
                    if (cardDTOs != null) {
                        combinedDTOs.addAll(cardDTOs);
                    } 
                } 

                Collections.sort(combinedDTOs);
                return combinedDTOs;
            } 
        } 
); 

Await.result(futureSum, Duration.Inf());  
return combinedDTOs; 

Right now we have around 4-5 parallel tasks per request. But it is expected to grow to almost 20-25 parallel tasks as we introduce new kinds of items in feed.

My question is, how can I improve this design? What kind of tuning is required in Tomcat to make sure such 20-25 parallel calls can be served optimally under heavy load.

I understand this is a broad topic, but any suggestions would be very helpful.

Answer 1

Tomcat just manages the incoming HTTP connections and pushes the bytes back and forth. There is no Tomcat optimization that can be done to make your application run any better.

If you need 25 parallel processes to run for each incoming HTTP request, and you think that's crazy, then you need to re-think how your application works.

No tomcat configuration will help with what you've presented in your question.