Async Spring Controllers vs normal Controllers

Question

I wanted to analyze the improvement I may see by enabling Async Controllers in Spring Boot over normal controller

So here is my test code. One API returns a Callable and another is normal controller API. Both APIs block for 10secs simulating a long running task

@RequestMapping(value="/api/1",method=RequestMethod.GET)
    public List<String> questions() throws InterruptedException{
        Thread.sleep(10000);
        return Arrays.asList("Question1","Question2");
    }

    @RequestMapping(value="/api/2",method=RequestMethod.GET)
    public Callable<List<String>> questionsAsync(){
        return () -> {
            Thread.sleep(10000);
            return Arrays.asList("Question2","Question2");
        };
    }

I set up embedded tomcat with this configuration i.e only one tomcat processing thread:

server.tomcat.max-threads=1
logging.level.org.springframework=debug

Expectations for /api/1 Since there is only one tomcat thread, another request will not be entertained untill this is processed after 10secs

Results: Meet expectations

Expectations for /api/2 Since we are returning a callable immediately, the single tomcat thread should get free to process another request. Callable would internally start a new thread. So if you hit the same api it should also gets accepted.

Results: This is not happening and untill the callable executes completely, no further request is entertained.

Question Why is /api/2 not behaving as expected?

@RomanC I mentioned in question, i set the tomcat's threadpool to contain only 1 thread. — hellojava
– hellojava, Commented Jun 18, 2016 at 14:49
Just to be sure: which kind of "other request" do you submit while the spring thread is sleeping? — JB Nizet
– JB Nizet, Commented Jun 18, 2016 at 16:19
You didn't actualy say how you tested your assertions. It works as expected for me (if I have 4 concurrent consumers I see roughly 4x more throughput with the async controller). I measured it with Apache bench running on a different machine than the server. — Dave Syer
– Dave Syer, Commented Jun 19, 2016 at 15:14
@DaveSyer Thanks. I tested with curl and I can see /api/2 behave as expected. As mentioned below, its infact an issue with chrome browser — hellojava
– hellojava, Commented Jun 21, 2016 at 17:21

Jakub Wach · Accepted Answer · 2016-06-19 23:49:52Z

14

@DaveSyer is right, /api/2 is actually behaving as expected.

I assume you are testing the behavior with a web browser. At least Firefox and Chrome are preventing multiple simultaneous requests to the same URL. If you open 2 tabs with api/2, the second one will only send a request to the application after the first got the response.

Try testing it with a simple bash script, like:

curl localhost/api/2 &
curl localhost/api/2 &
curl localhost/api/2 &

It will print 3 responses around the same time.

answered Jun 19, 2016 at 23:49

Jakub Wach

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1 Comment

hellojava Over a year ago

You and @DaveSyer are absolutely right! This issue is happening only in browser and not with curl or any http client test tool.

ouflak · Accepted Answer · 2022-03-16 18:55:09Z

0

Just want to mention that server.tomcat.max-threads is deprecated since Spring boot 2.3. Now use server.tomcat.threads.max in your Spring application.properties. The default is 200.

edited Mar 16, 2022 at 18:55

ouflak

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answered Mar 16, 2022 at 12:52

ARK

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