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)
Deprecated.
since 3.0. Use
ofInactivityGapAndGrace(Duration, Duration) instead |
long |
gracePeriodMs() |
int |
hashCode() |
long |
inactivityGap()
Return the specified gap for the session windows in milliseconds.
|
static SessionWindows |
ofInactivityGapAndGrace(Duration inactivityGap,
Duration afterWindowEnd)
Creates a new window specification with the specified inactivity gap.
|
static SessionWindows |
ofInactivityGapWithNoGrace(Duration inactivityGap)
Creates a new window specification with the specified inactivity gap.
|
String |
toString() |
static SessionWindows |
with(Duration inactivityGap)
Deprecated.
since 3.0. Use
ofInactivityGapWithNoGrace(Duration) instead |
public static SessionWindows ofInactivityGapWithNoGrace(Duration inactivityGap)
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.
CAUTION: Using this method implicitly sets the grace period to zero, which means that any out-of-order records arriving after the window ends are considered late and will be dropped.
inactivityGap - the gap of inactivity between sessionsIllegalArgumentException - if inactivityGap is zero or negative or can't be represented as long millisecondspublic static SessionWindows ofInactivityGapAndGrace(Duration inactivityGap, Duration afterWindowEnd)
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.
Using this method explicitly sets the grace period to the duration specified by afterWindowEnd, which
means that only out-of-order records arriving more than the grace period after the window end will be dropped.
The window close, after which any incoming records are considered late and will be rejected, is defined as
windowEnd + afterWindowEnd
inactivityGap - the gap of inactivity between sessionsafterWindowEnd - The grace period to admit out-of-order events to a window.IllegalArgumentException - if inactivityGap is zero or negative or can't be represented as long milliseconds
if afterWindowEnd is negative or can't be represented as long milliseconds@Deprecated public static SessionWindows with(Duration inactivityGap)
ofInactivityGapWithNoGrace(Duration) insteadinactivityGap - the gap of inactivity between sessionsinactivityGap)IllegalArgumentException - if inactivityGap is zero or negative or can't be represented as long milliseconds@Deprecated public SessionWindows grace(Duration afterWindowEnd) throws IllegalArgumentException
ofInactivityGapAndGrace(Duration, Duration) insteadafterWindowEnd
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 or can't be represented as long millisecondsIllegalStateException - if grace(Duration) is called after ofInactivityGapAndGrace(Duration, Duration) or ofInactivityGapWithNoGrace(Duration)public long gracePeriodMs()
public long inactivityGap()