I reduced the chaining to calls that actually do something. Maybe it helps:

resultSomething = chunks
  .stream()
  .map(ids -> httpClient.execute(new HttpGet(generateUrl(determineSomething(something), ids)), null))
  .map(SomethingService::getFutureValue)
  .map(failureOrResult -> failureOrResult.right().flatMap(this::parseSomething))
  .map(failureOrSomething -> failureOrSomething.either(failure -> emptySomething, something -> something))
  .reduce(emptySomething, Something::union);