RFR: 8072645: java.util.logging should use java.time to get more precise time stamps

[Peter Levart]

Hi Daniel,

The "millis" property in your proposal just changes one part of 
LogRecord's notion of time (it doesn't change/reset the nanoAdjustment 
part). From compatibility standpoint, your ptoposal is changing the 
semantics of "millis" property. Previously "millis" was the sole 
property of record's notion of time, now it is only a component of it. 
Consider this legacy code:

LogRecord r = new LogRecord(...); // timestamp1
...
r.setMillis(System.currentTimeMillis()); // timestamp2

What is the record's notion of time now? It is composed of "millis" from 
timestamp2 and "nanoAdjustment" from timestamp1. Not something that one 
would want, right?

So what should be done instead is:
- deprecate "millis" writable property and document that it sets the 
record's time with the resolution of milliseconds and point to new 
"instantUTC" property as a replacement.
- add "instantUTC" writable property and document it as "the" method to 
be used to set record's time with full resolution
- optionally add read-only "nanoAdjustment" property (I don't think it 
is needed, since users should start using new time API instead of 
mangling with millis and nanos themselves)

This lends itself to also change internal storage of LogRecord's time. 
You could just replace the "millis" field with a reference to 
"instantUTC". Serialization would have to be adjusted a bit (using 
serialPersistentFields) to stay compatible.

What do you think?

Regards, Peter

On 02/13/2015 03:56 PM, Daniel Fuchs wrote:
> Hi,
>
> Please find below a patch for:
>
> 8072645: java.util.logging should use java.time to get more
>          precise time stamps
>
>
> http://cr.openjdk.java.net/~dfuchs/webrev_8072645/webrev.00/
>
> specdiff:
> http://cr.openjdk.java.net/~dfuchs/webrev_8072645/specdiff-logging-time/java/util/logging/package-summary.html 
>
>
> Overview:
> ---------
>
> The patch is made of the following pieces:
>
>  - LogRecord uses java.time.Clock's systemClock to get an
>    Instant in the best available resolution.
>
>    The instant is split into a number of milliseconds (a long)
>    and a nanosecond adjustment (an int).
>    The number of milliseconds is the same than what would have
>    been obtained by calling System.currentTimeMillis().
>
>  - LogRecord acquires a new serializable int nanoAdjustement field,
>    which can be used together with the number of milliseconds
>    to reconstruct the instant.
>
>  - SimpleFormatter is updated to pass a ZoneDateTime
>    instance to String.format, instead of a Date.
>
>    The effect of that is that the format string can now
>    be configure to print the full instant precision, if
>    needed.
>
>  - XMLformatter will add a new <nanos> element after the
>    <millis> element - if the value of the nanoAdjustment
>    field is not 0.
>
>    The <date> string will also contain the nano second
>    adjustment as well as the zone offset as formatted by
>    DateTimeFormatter.ISO_OFFSET_DATE_TIME
>
> Compatibility considerations:
> -----------------------------
>
> - The serial for of log record is backward/forward compatible.
>   I added a test to verify that.
>
> - XMLFormatter has acquired a new configurable property
>   '<FQCN>.printNanos' which allows to revert to the old
>   XML format, should the new format cause issues in
>   existing applications.
>
> - The logger.dtd will need to be updated, to support the
>   new optional <nanos> element. And for this matter,
>   should we update the logger.dtd or rather define a
>   logger-v2.dtd?
>   See planned modification:
>
> <http://cr.openjdk.java.net/~dfuchs/webrev_8072645/logger-dtd/logger.dtd.frames.html> 
>
>
> best regards,
>
> -- daniel