logfellow
Add support for Timestamp with nanosecond precision (logback 1.3.0)
Starting from 1.3.0-alpha12, Logback events are now storing timestamp with nanosecond precision (using an Instant). The AbstractTimestampJsonProvider should be updated to take this enhancement into account.
A couple of questions/remarks...
(1) Backward compatibility
A new getInstant() method has been added to LoggingEvent in version 1.3.0 which was not available in previous versions.
Instead of providing two distincts artefacts (one for logback 1.2 and another for 1.3) I propose to keep only one and make use of reflection to detect at runtime if the getInstant() method is available and automatically enable nanosecond precision in our JsonProvider.
It should be noted that as of version 1.3.0-beta0 AccessEvents have not (yet) been enhanced with a getInstant() method and therefore lack nanosecond precision. Using the above mentioned strategy should help us to keep using the current AbstractFormattedTimestampJsonProvider as a base class for both the LoggingEvent and AccessEvent specialisations: getInstant() not available on AccessEvent -> nanosecond not enabled -> revert to millis as currently.
(2) Available timestamp formats and default
By default timestamps are formatted as [ISO_OFFSET_DATE_TIME]. As per the javadoc of java.time.format.DateTimeFormatter this format outputs nanoseconds but drops the insignificant leading zeros. This means that:
- precision will be at most three digits (milliseconds) when used with logback 1.2
- precision will be up to 9 digits (nanoseconds) when used with logback 1.3 Users should be aware they will suddenly have a higher timestamp precision just by upgrading the logback and LLE versions while keeping the same configuration. If nanosecond precision is not desired, users have the option of configuring an explicit format pattern instead of using the [ISO_OFFSET_DATE_TIME] keyword.
[UNIX_TIMESTAMP_AS_NUMBER] and [UNIX_TIMESTAMP_AS_STRING] will behave asis.
(3) Build, Testing and Dependencies
First phase: logback 1.3.0 still in BETA
Keep latest logback 1.2.x in the POM. Build against 1.2 - execute tests with 1.2 and 1.3 (same strategy as for Jackson)
Second phase: logback 1.3.0 is GA
Bump logback to 1.3.0 in POM. Build against 1.3 - execute tests with 1.3 and 1.2 (same strategy as for Jackson)
