RFR: 8289688: jfr command hangs when it processes invalid file

[Erik Gahlin]

On Tue, 12 Jul 2022 13:34:09 GMT, Yasumasa Suenaga <ysuenaga at openjdk.org> wrote:

> Did you say JVM would write recording file with random access? 

Yes, it writes the chunk header etc. using random access. 

>Even if that is the case, it means recording file might be "unreliable" when it conflicts reading / writing, isn't it?

Not if the parser follows a protocol where the file state is checked in the header. With JDK 14, JFR file format is streaming, but backward compatible for non-streaming parsers that only reads finished files.

The JDK parser can read a recording while it is being written. The JMC parser doesn't support streaming, so it would be incorrect to use that logic.

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PR: https://git.openjdk.org/jdk/pull/9363