Naïve Tomcat experiment--does this indicate pinning?

[Cay Horstmann]

Hi, I am running a simple experiment with Tomcat where one can easily 
replace the executor for what I presume are the threads for each servlet 
request. I use the following executor to which I submit all tasks:

       ThreadFactory myfactory = Thread.ofVirtual()
          .name("myfactory-", 1)
          .factory();
       exec = Executors.newThreadPerTaskExecutor(myfactory);

Now I run a servlet that sleeps for 100 ms and then returns 
Thread.currentThread().toString().

When I fire lots of concurrent requests at the servlet, those returned 
strings look like this:

VirtualThread[#13508,myfactory-13452]/runnable at ForkJoinPool-1-worker-16
VirtualThread[#13515,myfactory-13459]/runnable at ForkJoinPool-1-worker-16
VirtualThread[#13513,myfactory-13457]/runnable at ForkJoinPool-1-worker-11
VirtualThread[#13512,myfactory-13456]/runnable at ForkJoinPool-1-worker-15

I was hoping that making 10000 requests would result in 10000 tasks that 
would all complete after roughly 100 ms. But it takes over 2 minutes to 
complete.

So, now I am wondering whether it is possible that those threads acquire 
an object lock or do something else that pins them. After all, if not, 
why would they execute on different worker threads? How would one go 
about debugging such a scenario?

Cheers,

Cay

-- 

Cay S. Horstmann | http://horstmann.com | mailto:cay at horstmann.com