T- the type of items coming out of this stage
public interface StreamSourceStage<T>
pipelinethat will observe an unbounded amount of data (i.e., an event stream). Timestamp handling, a prerequisite for attaching data processing stages, is not yet defined in this step. Call one of the methods on this instance to declare whether and how the data source will assign timestamps to events.
|Modifier and Type||Method and Description|
Declares that the source will assign the time of ingestion as the event timestamp.
Declares that the stream will use the source's native timestamps.
Declares that the source will not assign any timestamp to the events it emits.
Declares that the source will extract timestamps from the stream items.
addTimestamps, but the behavior is different — see the note there.
default StreamStage<T> withIngestionTimestamps()
System.currentTimeMillis()at the moment it observes an event from the data source and assign it as the event timestamp.
Note: when snapshotting is enabled to achieve fault
tolerance, after a restart Jet replays all the events that were already
processed since the last snapshot. These events will then get different
timestamps. If you want your job to be fault-tolerant, the events in the
stream must have a stable timestamp associated with them. The source may
natively provide such timestamps (the
option). If that is not appropriate, the events should carry their own
timestamp as a part of their data and you can use
withTimestamps(timestampFn, allowedLag to extract it.
Note 2: if the system time goes back (such as when adjusting it), newer events will get older timestamps and might be dropped as late, because the allowed lag is 0.
StreamStage<T> withNativeTimestamps(long allowedLag)
If there's no notion of native timestamps in the source, this method
will throw a
allowedLag- the allowed lag of a given event's timestamp behind the top timestamp value observed so far
StreamStage<T> withTimestamps(@Nonnull ToLongFunctionEx<? super T> timestampFn, long allowedLag)
timestampFn- a function that returns the timestamp for each item, typically in milliseconds
allowedLag- the allowed lag of a given event's timestamp behind the top timestamp value observed so far. The time unit is the same as the unit used by
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