Lighting talk about async http handling in SpringMVC and it's relation to "Reactive" buzz from 02-12-2014

1. On performance of random
and thread contention
Dmytro_Aleksandrov@epam.com
Link to source 1

2. Monte-carlo simulation
2

3. Monte-carlo simulation
3
java.util.Random – 1 per thread:
1 thread ~ 80 sec
2 threads~ 45 sec
4 threads~ 26 sec
ThreadLocalRandom:
1 thread ~ 8 sec
2 threads~ 4 sec
4 threads~ 2 sec

4. Summary
4
java.util.Random:
• thread-safe aka synchronized
• AtomicLong as seed
java.util.concurrent.ThreadLocalRandom:
• UNSAFE long as seed
Link to source: http://java-performance.info/java-util-random-java-util-concurrent-threadlocalrandom-multithreaded-environments/

5. Not yet reactive but
asynchronous MVC
Dmytro_Aleksandrov@epam.com
Link to source 5

6. Signature of ‘typical’ @RequestMapping
6
@RequestMapping(value = "/user", method = RequestMethod.GET)
public String getUser()
Link to source: http://docs.spring.io/spring/docs/current/spring-framework-reference/html/mvc.html

7. How does it processed
7
• Threaded model
Link to source: http://www.oracle.com/technetwork/articles/grid/asynchronous-servlets-088344.html

8. Now imagine a service
8
@RestController
class EventsController {
}
def fastEvent(): Event =
{…}
def blockingOp(): Int = {…}

9. Now imagine a service
9
def blockingOp(): Int = {
val processingTime = ThreadLocalRandom.current.nextInt(1000, 2000)
// IO bounded operation intended here
Thread.sleep(processingTime)
processingTime
}
def fakeEvent(): Event = {
Event("fakeId", System.currentTimeMillis, Array.empty)
}
With one “heavy” operation
And a light one

10. Load test sample
10
Link to source: http://goo.gl/abYAO8

11. Side note
11
Link to source: http://gatling.io/
Load test are written in Gatling
Try to simulate C10K with JMeter
threaded model, again
Why not Jmeter?
Link to source: https://github.com/alkersan/timebench/blob/master/modules/loadtest/src/test/scala/SpringBootSimulation.scala

12. Asynchronous completion
12
@RequestMapping(value = "/user", method = RequestMethod.GET)
public Callable<String> getUser()
• Servlet 3.0 and 3.1
• Spring 3.2
Simply change signature to utilize this:
or Future<T>
or DeferredResult<T>
Link to source: http://docs.spring.io p.17.3.4

13. What’s changed under load
13
Link to source: http://goo.gl/hYl0Ie

14. SLA
14
def fakeEvent(): Event = {
Event("fakeId", System.currentTimeMillis, Array.empty)
}
Light operations:
Can be served under load

15. Why this still is not “reactive”?
15
Because in reality it doesn’t solve the reason of blocking
}
def blockingOp(): Int = {
// JDBC call
// or Remote WS call
// or File IO
// or remote RPC call

16. For example: SpringData-Elastic call
16
• Intuitive interface
• Reduces boilerplate
public interface UserRepository extends
CrudRepository<User, Long> {
Long deleteByLastname(String lastname);
List<User> removeByLastname(String lastname);
}
Link to source: http://docs.spring.io/spring-data/elasticsearch/docs/1.1.0.M1/reference/htmlsingle/

17. “Doubt everything we know”
- Descartes
17
Basic construct is:
ElasticsearchTemplate
public <T> Page<T> queryForPage (StringQuery query, …args…, ..args…) {
SearchResponse response = repareSearch(query,clazz)
.setQuery(query.getSource())
.execute()
.actionGet();
return mapper.mapResults(response, clazz, query.getPageable());
}
ListenableFuture
Synchronously Awaits
(i.e. Blocks!)
Link to source: https://github.com/spring-projects/spring-data-elasticsearch

18. Conclusion
18
Always look under the hood