Make sure all tests pass when io_uring is enabled

[trustin]

Armeria allows a user to choose the underlying transport type between nio, epoll and io_uring, defaulting to epoll on Linux and nio on other OSes. Armeria does not select io_uring even if the current Linux kernel has io_uring support, mainly because there were some test failures when we switched to io_uring.

We need to fix any test failures that occur when io_uring is used, and make it the default transport type on Linux for potentially better performance.

Currently, you can enable io_uring for all tests by inserting two lines in /build.gradle:

def isCi = System.getenv("CI") != null
allprojects {
    // Add common JVM options such as max memory and leak detection.
    tasks.withType(JavaForkOptions) {
        ...
        // Enable io_uring by default (only effective in Linux kernel 5.1+) // 👈👈👈
        systemProperties 'com.linecorp.armeria.transportType': 'io_uring'   // 👈👈👈
    }
    ...

You can confirm io_uring is actually in use from the log message like the following:

INFO  com.linecorp.armeria.common.Flags - transportType: IO_URING (sysprops)

Also, the event loop thread names will have -io_uring, e.g. armeria-common-worker-io_uring-3-6.

[trustin]

@dachshu, you told me you're interested in this issue last week, right? 😉