Concurrent requests for blocking reactive routes is limited by quarkus.vertx.event-loops-pool-size

[timoesk]

Describe the bug

Concurrent requests for blocking reactive routes is limited by quarkus.vertx.event-loops-pool-size

Expected behavior

Concurrent requests for blocking reactive routes should be limited by quarkus.vertx.worker-pool-size

Actual behavior

When a blocking route is created with the the Route annotation.

@Route(path = "/blocking-with-annotation", methods = HttpMethod.GET, type = Route.HandlerType.BLOCKING)

Then the concurrent HTTP requests are limited by the number of event loops.

To Reproduce

See ReactiveRoutesTest.java in:

https://github.com/timoesk/quarkus-reactive-routes-issue

[gsmet]

/cc @johnaohara @cescoffier

[gsmet]

maybe /cc @stuartwdouglas too

[timoesk]

I noticed that SmallRye Metrics extension has the same issue. The concurrent requests for the metrics API are also limited by the number of event loops.

2020-06-26 14:56:22,293 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-19) Requesting 6
2020-06-26 14:56:22,293 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-9) Requesting 5
2020-06-26 14:56:22,295 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-13) Requesting 1
2020-06-26 14:56:22,295 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-23) Requesting 8
2020-06-26 14:56:22,295 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-3) Requesting 0
2020-06-26 14:56:22,295 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-17) Requesting 9
2020-06-26 14:56:22,295 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-5) Requesting 2
2020-06-26 14:56:22,296 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-31) Requesting 3
2020-06-26 14:56:22,295 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-21) Requesting 7
2020-06-26 14:56:22,295 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-27) Requesting 4
Handling http://localhost:8081/metrics?i=2 on thread vert.x-worker-thread-1
2020-06-26 14:56:22,473 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-5) Completed 2
Handling http://localhost:8081/metrics?i=0 on thread vert.x-worker-thread-1
2020-06-26 14:56:22,538 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-3) Completed 0
Handling http://localhost:8081/metrics?i=5 on thread vert.x-worker-thread-1
2020-06-26 14:56:22,606 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-9) Completed 5
Handling http://localhost:8081/metrics?i=4 on thread vert.x-worker-thread-1
2020-06-26 14:56:22,694 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-27) Completed 4
Handling http://localhost:8081/metrics?i=6 on thread vert.x-worker-thread-1
2020-06-26 14:56:22,763 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-19) Completed 6
Handling http://localhost:8081/metrics?i=8 on thread vert.x-worker-thread-1
2020-06-26 14:56:22,833 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-23) Completed 8
Handling http://localhost:8081/metrics?i=1 on thread vert.x-worker-thread-1
2020-06-26 14:56:22,903 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-13) Completed 1
Handling http://localhost:8081/metrics?i=9 on thread vert.x-worker-thread-1
2020-06-26 14:56:22,968 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-17) Completed 9
Handling http://localhost:8081/metrics?i=3 on thread vert.x-worker-thread-1
2020-06-26 14:56:23,039 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-31) Completed 3
Handling http://localhost:8081/metrics?i=7 on thread vert.x-worker-thread-1
2020-06-26 14:56:23,303 INFO  [org.acm.MetricsTest] (ForkJoinPool-2-worker-21) Completed 7

I used debugger to print the worker thread.

Is this related to the blocking reactive routes issue?

[cescoffier]

It's related to the @Route annotation.

I've tried the reproducer and changed the code a bit to display the value of the counter. Using the regular route (registered on the router) I got 20. However, with the @Route it does not go above 1.

[cescoffier]

Found the issue... our blocking handler are registered with ordered set to true, which means it waits for one task to complete before executing the next task.

[cescoffier]

I've submitted a fix: #10310

[timoesk]

That was fast. Thanks!

[cescoffier]

@timoesk BTW, yes, it would fix the metrics issue too.