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moving docs #624 to kap #851

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merged 3 commits into from
Aug 31, 2016
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moving docs #624 to kap #851

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b3e8ca1
moving docs #624 to kap
beckettsean Aug 30, 2016
68148e2
Update window.go
beckettsean Aug 30, 2016
f003926
Update window.go
beckettsean Aug 30, 2016
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31 changes: 19 additions & 12 deletions pipeline/window.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,15 @@ import (
"time"
)

// Windows data over time.
// A window has a length defined by `period`
// and a frequency at which it emits the window to the pipeline.
// A `window` node caches data within a moving time range.
// The `period` property of `window` defines the time range covered by `window`.
//
// The `every` property of `window` defines the frequency at which the window
// is emitted to the next node in the pipeline.
//
//The `align` property of `window` defines how to align the window edges.
//(By default, the edges are defined relative to the first data point the `window`
//node receives.)
//
// Example:
// stream
Expand All @@ -15,13 +21,11 @@ import (
// .every(5m)
// |httpOut('recent')
//
// The above windowing example emits a window to the pipeline every `5 minutes`
// and the window contains the last `10 minutes` worth of data.
// As a result each time the window is emitted it contains half new data and half old data.
// his example emits the last `10 minute` period every `5 minutes` to the pipeline's `httpOut` node.
// Because `every` is less than `period`, each time the window is emitted it contains `5 minutes` of
// new data and `5 minutes` of the previous period's data.
//
// NOTE: Time for a window (or any node) is implemented by inspecting the times on the incoming data points.
// As a result if the incoming data stream stops then no more windows will be emitted because time is no longer
// increasing for the window node.
// NOTE: Because no `align` property is defined, the `window` edge is defined relative to the first data point.
type WindowNode struct {
chainnode
// The period, or length in time, of the window.
Expand All @@ -39,9 +43,12 @@ func newWindowNode() *WindowNode {
}
}

// Wether to align the window edges with the zero time.
// If not aligned the window starts and ends relative to the
// first data point it receives.
// If the `align` property is not used to modify the `window` node, then the
// window alignment is assumed to start at the time of the first data point it receives.
// If `align` property is set, the window time edges
// will be truncated to the `every` property (For example, if a data point's time
// is 12:06 and the `every` property is `5m` then the data point's window will range
// from 12:05 to 12:10).
// tick:property
func (w *WindowNode) Align() *WindowNode {
w.AlignFlag = true
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