[jdk18] RFR: 8268297: jdk/jfr/api/consumer/streaming/TestLatestEvent.java times out

[Erik Gahlin]

Hi,

Could I have a review of a fix that prevents a recording stream from dropping events/chunks. 

This occurs when rotation happens quickly, as in TestLatestEvent.java, and the clock is not making progress, on Windows sometimes. The result is a chunk header with duration 0 ns, meaning there could be two chunks with the same start timestamp, which confuses the RecordingStream when determining iteration order.

The fix is to always increase the elapsed time by at least 1 ns. There were similar code prior to JDK 17, but it was removed because a mechanism was added in Java that makes sure a chunk always gets a unique Instant.now() timestamp. Unfortunately, that timestamp does not always correlate with what the JVM writes, which leads to intermittent failures in 2-4% of the time. 

I also updated the test, so it can provide better information in case of new failures.

Testing:  
test/jdk/jdk/jfr/api/consumer/streaming/TestLatestEvent.java 600 times without failure on Windows
test/jdk/jdk/jfr/ 6 times without failure on Mac, Linux and Windows.

Thanks
Erik

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Commit messages:
 - Initial

Changes: https://git.openjdk.java.net/jdk18/pull/68/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18&pr=68&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268297
  Stats: 24 lines in 3 files changed: 20 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk18/pull/68.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18 pull/68/head:pull/68

PR: https://git.openjdk.java.net/jdk18/pull/68