public final class SessionWindows extends Object
Sessions represent a period of activity separated by a defined gap of inactivity. Any events processed that fall within the inactivity gap of any existing sessions are merged into the existing sessions. If the event falls outside of the session gap then a new session will be created.
For example, if we have a session gap of 5 and the following data arrives:
+--------------------------------------+ | key | value | time | +-----------+-------------+------------+ | A | 1 | 10 | +-----------+-------------+------------+ | A | 2 | 12 | +-----------+-------------+------------+ | A | 3 | 20 | +-----------+-------------+------------+We'd have 2 sessions for key A. One starting from time 10 and ending at time 12 and another starting and ending at time 20. The length of the session is driven by the timestamps of the data within the session. Thus, session windows are no fixed-size windows (c.f.
TimeWindows
and JoinWindows
).
If we then received another record:
+--------------------------------------+ | key | value | time | +-----------+-------------+------------+ | A | 4 | 16 | +-----------+-------------+------------+The previous 2 sessions would be merged into a single session with start time 10 and end time 20. The aggregate value for this session would be the result of aggregating all 4 values.
For time semantics, see TimestampExtractor
.
Modifier and Type | Method and Description |
---|---|
boolean |
equals(Object o) |
SessionWindows |
grace(Duration afterWindowEnd)
Reject out-of-order events that arrive more than
afterWindowEnd
after the end of its window. |
long |
gracePeriodMs() |
int |
hashCode() |
long |
inactivityGap()
Return the specified gap for the session windows in milliseconds.
|
long |
maintainMs()
Deprecated.
since 2.1. Use
Materialized.retention instead. |
String |
toString() |
SessionWindows |
until(long durationMs)
Deprecated.
since 2.1. Use
Materialized.retention
or directly configure the retention in a store supplier and use
Materialized.as(SessionBytesStoreSupplier) . |
static SessionWindows |
with(Duration inactivityGap)
Create a new window specification with the specified inactivity gap.
|
static SessionWindows |
with(long inactivityGapMs)
Deprecated.
Use
with(Duration) instead. |
@Deprecated public static SessionWindows with(long inactivityGapMs)
with(Duration)
instead.inactivityGapMs
- the gap of inactivity between sessions in millisecondsIllegalArgumentException
- if inactivityGapMs
is zero or negativepublic static SessionWindows with(Duration inactivityGap)
inactivityGap
- the gap of inactivity between sessionsIllegalArgumentException
- if inactivityGap
is zero or negative or can't be represented as long milliseconds
@Deprecated public SessionWindows until(long durationMs) throws IllegalArgumentException
Materialized.retention
or directly configure the retention in a store supplier and use
Materialized.as(SessionBytesStoreSupplier)
.IllegalArgumentException
- if durationMs
is smaller than window gappublic SessionWindows grace(Duration afterWindowEnd) throws IllegalArgumentException
afterWindowEnd
after the end of its window.
Note that new events may change the boundaries of session windows, so aggressive close times can lead to surprising results in which an out-of-order event is rejected and then a subsequent event moves the window boundary forward.
afterWindowEnd
- The grace period to admit out-of-order events to a window.IllegalArgumentException
- if the afterWindowEnd
is negative of can't be represented as long milliseconds
public long gracePeriodMs()
public long inactivityGap()
@Deprecated public long maintainMs()
Materialized.retention
instead.
For SessionWindows
the maintain duration is at least as small as the window gap.