Best way to limit time execution in a #RestController - spring

Question

Considering the following code:
#RestController
#RequestMapping("/timeout")
public class TestController {
#Autowired
private TestService service;
#GetMapping("/max10secs")
public String max10secs() {
//In some cases it can take more than 10 seconds
return service.call();
}
}
#Service
public class TestService {
public String call() {
//some business logic here
return response;
}
}
What I want to accomplish is that if the method call from the TestService takes more than 10 seconds I want to cancel it and generate a response with a HttpStatus.REQUEST_TIMEOUT code.

Answer 1

What I managed to do, but I don't know if there are any conceptual or practical flaws is what it follows...
First, the configuration of spring-async
#Configuration
#EnableAsync
public class AsyncConfig implements AsyncConfigurer {
#Bean(name = "threadPoolTaskExecutor")
public Executor threadPoolTaskExecutor() {
ThreadPoolTaskExecutor pool = new ThreadPoolTaskExecutor();
pool.setCorePoolSize(10);
pool.setMaxPoolSize(10);
pool.setWaitForTasksToCompleteOnShutdown(true);
return pool;
}
#Override
public Executor getAsyncExecutor() {
return new SimpleAsyncTaskExecutor();
}
}
And next, the Controller and Service modifications:
#RestController
#RequestMapping("/timeout")
public class TestController {
#Autowired
private TestService service;
#GetMapping("/max10secs")
public String max10secs() throws InterruptedException, ExecutionException {
Future<String> futureResponse = service.call();
try {
//gives 10 seconds to finish the methods execution
return futureResponse.get(10, TimeUnit.SECONDS);
} catch (TimeoutException te) {
//in case it takes longer we cancel the request and check if the method is not done
if (futureResponse.cancel(true) || !futureResponse.isDone())
throw new TestTimeoutException();
else {
return futureResponse.get();
}
}
}
}
#Service
public class TestService {
#Async("threadPoolTaskExecutor")
public Future<String> call() {
try{
//some business logic here
return new AsyncResult<>(response);
} catch (Exception e) {
//some cancel/rollback logic when the request is cancelled
return null;
}
}
}
And finally generate the TestTimeoutException:
#ResponseStatus(value = HttpStatus.REQUEST_TIMEOUT, reason = "too much time")
public class TestTimeoutException extends RuntimeException{ }

Answer 2

There is another solution via DeferredResult.
TestController.java
#RestController
#RequestMapping("/timeout")
public class TestController
{
#Autowired
private TestService service;
#GetMapping("/max10secs")
public DeferredResult<String> max10secs()
{
//In some cases it can take more than 10 seconds
return service.call();
}
}
TestService.java
#Service
public class TestService
{
public DeferredResult<String> call()
{
DeferredResult<String> result = new DeferredResult(10000L);
//some business logic here
result.onTimeout(()->{
// do whatever you want there
});
result.setResult("test");
return result;
}
}
This way, controller will return actual result only when you call result.setResult("test");.
As you can see, in case of timeout (value for timeout is defined in constructor of DeferredResult object in milliseconds) there will be a callback executed where you can throw any exception, or return another object(HttpStatus.REQUEST_TIMEOUT in your case).
You can read about the DeferredResult in Spring here.