Retrieves embedded metadata timestamps from Kafka messages.
If a record has a negative (invalid) timestamp value, this extractor raises an exception.
Embedded metadata timestamp was introduced in "KIP-32: Add timestamps to Kafka message" for the new
0.10+ Kafka message format.
Here, "embedded metadata" refers to the fact that compatible Kafka producer clients automatically and
transparently embed such timestamps into message metadata they send to Kafka, which can then be retrieved
via this timestamp extractor.
If the embedded metadata timestamp represents CreateTime (cf. Kafka broker setting
message.timestamp.type and Kafka topic setting
log.message.timestamp.type),
this extractor effectively provides event-time semantics.
If LogAppendTime is used as broker/topic setting to define the embedded metadata timestamps,
using this extractor effectively provides ingestion-time semantics.
If you need processing-time semantics, use
WallclockTimestampExtractor.