Autoconfigure Undertow/XNIO for virtual thread support

[g-dx]

Hi,

With the release of Spring Boot 3.2 a new property spring.threads.virtual.enabled was added which, amongst other classes, configured Tomcat and Jetty HTTP request handling to be performed using a virtual thread executor.

Are there any plans to also provide out of the box support for Undertow?

[philwebb]

I believe we may have looked into it but couldn't find the same kind of virtual thread support that Tomcat and Jetty were offering. @g-dx Have you seen any examples of how to configure Undertow to make use of virtual threads?

[ChunMengLu]

@philwebb @g-dx How about this:

@Bean
public UndertowDeploymentInfoCustomizer undertowDeploymentInfoCustomizer() {
 return deploymentInfo -> deploymentInfo.setExecutor(Executors.newVirtualThreadPerTaskExecutor());
}

[wilkinsona]

Thanks, @ChunMengLu. We'll look at doing this automatically in Spring Boot 3.3.

[mhalbritter]

As discovered in #39812, the approach with the executor doesn't work, as it leaks memory. I had to revert the change.

[dheeraj29]

Seems like memory issue is partially solved with https://issues.redhat.com/browse/UNDERTOW-2309 in 2.3.11 but still there is one open bug which occured with above release and tracked under https://issues.redhat.com/browse/UNDERTOW-2389

Once UNDERTWO-2389 is fixed, maybe virtual threads can be re-tested.

[philwebb]

#39812 (comment) has noted that both undertow issues are now fixed.

[mhalbritter]

Yes, this now looks good. I've run some tests with virtual threads enabled and -Xmx256M. I don't see any exceptions in the log, the plot looks okay and the request rate is reasonable, too.

Summary:
  Total:	30.0004 secs
  Slowest:	0.1469 secs
  Fastest:	0.0000 secs
  Average:	0.0015 secs
  Requests/sec:	123590.2974
  
  Total data:	111221646 bytes
  Size/request:	111 bytes

Response time histogram:
  0.000 [1]	|
  0.015 [995518]	|■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■
  0.029 [3175]	|
  0.044 [853]	|
  0.059 [217]	|
  0.073 [118]	|
  0.088 [68]	|
  0.103 [0]	|
  0.118 [0]	|
  0.132 [0]	|
  0.147 [50]	|


Latency distribution:
  10% in 0.0001 secs
  25% in 0.0001 secs
  50% in 0.0002 secs
  75% in 0.0003 secs
  90% in 0.0006 secs
  95% in 0.0009 secs
  99% in 0.0034 secs

Details (average, fastest, slowest):
  DNS+dialup:	0.0000 secs, 0.0000 secs, 0.1469 secs
  DNS-lookup:	0.0000 secs, 0.0000 secs, 0.0004 secs
  req write:	0.0000 secs, 0.0000 secs, 0.0031 secs
  resp wait:	0.0012 secs, 0.0000 secs, 0.1466 secs
  resp read:	0.0001 secs, 0.0000 secs, 0.0037 secs

Status code distribution:
  [200]	1000000 responses

[mhalbritter]

We need to wait for an Undertow version which has the fix for https://issues.redhat.com/browse/UNDERTOW-2420 in it.

[mhalbritter]

We have decided to ignore UNDERTOW-2420 and have upgraded the Undertow version in #42302 - so this issue can be tackled now.