RFR: 8325502: JFR: The type of EventSystemProcess::pid should be long

[Erik Gahlin]

On Thu, 8 Feb 2024 14:45:05 GMT, Denghui Dong <ddong at openjdk.org> wrote:

> Hi,
> 
> Please review this patch that changes the type of `EventSystemProcess::pid` to `long`
> 
> Thanks

If the System Process event was new, it would make sense to make the pid field use a long type, but when the event was introduced in Oracle JDK 7u40, there was no ProcessHandle API, only com.sun.tools.attach.VirtualMachine::id() which returns a string value. The benefit of using a long value seems small compared to all the existing code that might break with a ClassCastException, i.e.

    String pid = event.getValue("pid")
    
and the trouble of always checking the type in case the recording is older, i.e.

    long pid;
    if (event.getEventType().getField("pid").getTypeName().equals("java.lang.String")) {
        pid = Long.parseLong(event.getString("pid"));
    } else {
        pid = event.getLong("pid").
    }
    
Furthermore, there seeems to be a bug in JMC which renders long values in scientific notation, so user may not be able to read the value if it's changed.

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PR Comment: https://git.openjdk.org/jdk/pull/17773#issuecomment-1934828046