Package org.apache.kafka.streams.kstream

Class TimeWindows

  • public final class TimeWindows
extends Windows<org.apache.kafka.streams.kstream.internals.TimeWindow>
    The fixed-size time-based window specifications used for aggregations.

    The semantics of time-based aggregation windows are: Every T1 (advance) milliseconds, compute the aggregate total for T2 (size) milliseconds.

    • If advance < size a hopping windows is defined:
      it discretize a stream into overlapping windows, which implies that a record maybe contained in one and or more "adjacent" windows.
    • If advance == size a tumbling window is defined:
      it discretize a stream into non-overlapping windows, which implies that a record is only ever contained in one and only one tumbling window.
    Thus, the specified TimeWindows are aligned to the epoch. Aligned to the epoch means, that the first window starts at timestamp zero. For example, hopping windows with size of 5000ms and advance of 3000ms, have window boundaries [0;5000),[3000;8000),... and not [1000;6000),[4000;9000),... or even something "random" like [1452;6452),[4452;9452),...

    For time semantics, see TimestampExtractor.

    See Also:
    SessionWindows, UnlimitedWindows, JoinWindows, KGroupedStream.windowedBy(Windows), TimestampExtractor

    • Field Summary

      Fields 
      Modifier and Type Field Description
      long advanceMs
      The size of the window's advance interval in milliseconds, i.e., by how much a window moves forward relative to the previous one.
      long sizeMs
      The size of the windows in milliseconds.

      • Fields inherited from class org.apache.kafka.streams.kstream.Windows

        segments

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      TimeWindows advanceBy​(long advanceMs)
      Return a window definition with the original size, but advance ("hop") the window by the given interval, which specifies by how much a window moves forward relative to the previous one.
      boolean equals​(java.lang.Object o)  
      int hashCode()  
      long maintainMs()
      Return the window maintain duration (retention time) in milliseconds.
      static TimeWindows of​(long sizeMs)
      Return a window definition with the given window size, and with the advance interval being equal to the window size.
      long size()
      Return the size of the specified windows in milliseconds.
      TimeWindows until​(long durationMs)
      Set the window maintain duration (retention time) in milliseconds.
      java.util.Map<java.lang.Long,​org.apache.kafka.streams.kstream.internals.TimeWindow> windowsFor​(long timestamp)
      Create all windows that contain the provided timestamp, indexed by non-negative window start timestamps.

      • Methods inherited from class org.apache.kafka.streams.kstream.Windows

        segments

      • Methods inherited from class java.lang.Object

        clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • sizeMs

        public final long sizeMs
        The size of the windows in milliseconds.

      • advanceMs

        public final long advanceMs
        The size of the window's advance interval in milliseconds, i.e., by how much a window moves forward relative to the previous one.

    • Method Detail

      • of

        public static TimeWindows of​(long sizeMs)
                      throws java.lang.IllegalArgumentException
        Return a window definition with the given window size, and with the advance interval being equal to the window size. The time interval represented by the N-th window is: [N * size, N * size + size).

        This provides the semantics of tumbling windows, which are fixed-sized, gap-less, non-overlapping windows. Tumbling windows are a special case of hopping windows with advance == size.

        Parameters:
        sizeMs - The size of the window in milliseconds
        Returns:
        a new window definition with default maintain duration of 1 day
        Throws:
        java.lang.IllegalArgumentException - if the specified window size is zero or negative

      • advanceBy

        public TimeWindows advanceBy​(long advanceMs)
        Return a window definition with the original size, but advance ("hop") the window by the given interval, which specifies by how much a window moves forward relative to the previous one. The time interval represented by the N-th window is: [N * advance, N * advance + size).

        This provides the semantics of hopping windows, which are fixed-sized, overlapping windows.

        Parameters:
        advanceMs - The advance interval ("hop") in milliseconds of the window, with the requirement that 0 < advanceMs &le; sizeMs.
        Returns:
        a new window definition with default maintain duration of 1 day
        Throws:
        java.lang.IllegalArgumentException - if the advance interval is negative, zero, or larger-or-equal the window size

      • windowsFor

        public java.util.Map<java.lang.Long,​org.apache.kafka.streams.kstream.internals.TimeWindow> windowsFor​(long timestamp)
        Description copied from class: Windows
        Create all windows that contain the provided timestamp, indexed by non-negative window start timestamps.
        Specified by:
        windowsFor in class Windows<org.apache.kafka.streams.kstream.internals.TimeWindow>
        Parameters:
        timestamp - the timestamp window should get created for
        Returns:
        a map of windowStartTimestamp -> Window entries

      • size

        public long size()
        Description copied from class: Windows
        Return the size of the specified windows in milliseconds.
        Specified by:
        size in class Windows<org.apache.kafka.streams.kstream.internals.TimeWindow>
        Returns:
        the size of the specified windows

      • until

        public TimeWindows until​(long durationMs)
                  throws java.lang.IllegalArgumentException
        Description copied from class: Windows
        Set the window maintain duration (retention time) in milliseconds. This retention time is a guaranteed lower bound for how long a window will be maintained.
        Overrides:
        until in class Windows<org.apache.kafka.streams.kstream.internals.TimeWindow>
        Parameters:
        durationMs - the window retention time
        Returns:
        itself
        Throws:
        java.lang.IllegalArgumentException - if duration is smaller than the window size

      • maintainMs

        public long maintainMs()
        Return the window maintain duration (retention time) in milliseconds.

        For TimeWindows the maintain duration is at least as small as the window size.

        Overrides:
        maintainMs in class Windows<org.apache.kafka.streams.kstream.internals.TimeWindow>
        Returns:
        the window maintain duration

      • equals

        public boolean equals​(java.lang.Object o)
        Overrides:
        equals in class java.lang.Object

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class java.lang.Object