The following test timed out in the JDK15 CI:

java/nio/channels/DatagramChannel/Connect.java

Here's a snippet from the log file:

#section:main
----------messages:(8/217)----------
command: main Connect
reason: Assumed action based on file name: run main Connect
Mode: agentvm
Agent id: 9
Timeout refired 480 times
Timeout information:
--- Timeout information end.
elapsed time (seconds): 578.705
----------configuration:(11/1218)----------
Boot Layer
  class path: /scratch/mesos/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/javatest.jar
              /scratch/mesos/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/jtreg.jar
              /scratch/mesos/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/junit.jar
              /scratch/mesos/jib-master/install/jtreg/5.1/b01/bundles/jtreg_bin-5.1.zip/jtreg/lib/testng.jar
  patch: java.base /scratch/mesos/slaves/63712a43-4eaa-429c-95b4-483ac8241123-S962/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/2cddb8ad-a08a-478c-ad0f-9c969cdf5492/runs/e81d1ee2-96ab-4acf-adb3-58b969b246e0/testoutput/test-support/jtreg_open_test_jdk_tier2_part2/patches/java.base

Test Layer
  class path: /scratch/mesos/slaves/63712a43-4eaa-429c-95b4-483ac8241123-S962/frameworks/1735e8a2-a1db-478c-8104-60c8b0af87dd-0196/executors/2cddb8ad-a08a-478c-ad0f-9c969cdf5492/runs/e81d1ee2-96ab-4acf-adb3-58b969b246e0/testoutput/test-support/jtreg_open_test_jdk_tier2_part2/classes/0/java/nio/channels/DatagramChannel/Connect.d
              /scratch/mesos/jib-master/install/jdk-15+28-1386/src.full/open/test/jdk/java/nio/channels/DatagramChannel

----------rerun:(30/4064)*----------

The log file has no indicators of why the test timed out. I did
a quick check for this history of this test and most runs take
less than one second.