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Status
Current state: "Under Discussion"
Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]
JIRA: KAFKA-13511
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Motivation
TimestampConverter should have a config to define which precision to use when convert from and to Long epoch timestamps.
Currently, the Kafka Connect SMT TimestampConverter can convert Timestamp from multiples sources types (String, Long or Date) into different target types (String, Long or Date).
The problem is that Long as a source or as a target type is required to be epoch in milliseconds.
In many cases, epoch is represented with different precisions within external systems : seconds, milliseconds, microseconds, nanoseconds
This issue was raised several times :
Public Interfaces
epoch.precision
, default millis
Proposed Changes
New config property for TimestampConverter
"transforms.TimestampConverter.type": "org.apache.kafka.connect.transforms.TimestampConverter$Value", "transforms.TimestampConverter.field": "event_date_long", "transforms.TimestampConverter.epoch.precision": "micros", "transforms.TimestampConverter.target.type": "Timestamp"
int32 and seconds
Since int32 should not be used for timestamp, obsolete systems that produces int32 into Kafka and want should willingly chain Cast SMT and then TimestampConverter SMT if they want to use this feature.
"transforms": "Cast,TimestampConverter", "transforms.Cast.type": "org.apache.kafka.connect.transforms.Cast$Value", "transforms.Cast.spec": "event_date_int:int64", "transforms.TimestampConverter.type": "org.apache.kafka.connect.transforms.TimestampConverter$Value", "transforms.TimestampConverter.field": "event_date_int", "transforms.TimestampConverter.epoch.precision": "seconds", "transforms.TimestampConverter.target.type": "Timestamp"
java.util.Date and SimpleDateFormat limitations
Since these classes can only handle precisions down to the millisecond, it should be stated that:
- converting Long microseconds into any target type leads to a precision loss (truncation after millis)
- converting any source type into Long microseconds, the microseconds part will always be 000
This raises an interesting question (out of the scope of this KIP I guess) regarding the future of java.util.Date
Compatibility, Deprecation, and Migration Plan
The change will not break the compatibility.
Rejected Alternatives
If there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.