---
title: BarrierNode (Kapacitor TICKscript node)
description: BarrierNode emits a barrier with the current time, according to the system clock, and allows pipelines to be forced in the absence of data traffic. The barrier emitted will be based on either idle time since the last received message or on a periodic timer based on the system clock.
note: Auto generated by tickdoc

menu:
  kapacitor_1_4:
    name: BarrierNode
    identifier: barrier_node
    weight: 20
    parent: TICKscript nodes
---
### Constructor

| Chaining Method | Description |
|:---------|:---------|
| **[barrier](#descr) ( )** | Create a new Barrier node that emits a BarrierMessage periodically  |

### Property Methods

| Setters | Description |
|:---|:---|
| **[idle](#idle) ( `value` `time.Duration`)** | Emit barrier based on idle time since the last received message. Must be greater than zero **and longer than the window `period`**.  |
| **[period](#period) ( `value` `time.Duration`)** | Emit barrier based on periodic timer.  The timer is based on system clock rather than message time. Must be greater than zero.  |



### Chaining Methods
[Alert](/kapacitor/v1.4/nodes/barrier_node/#alert), [Barrier](/kapacitor/v1.4/nodes/barrier_node/#barrier), [Bottom](/kapacitor/v1.4/nodes/barrier_node/#bottom), [Combine](/kapacitor/v1.4/nodes/barrier_node/#combine), [Count](/kapacitor/v1.4/nodes/barrier_node/#count), [CumulativeSum](/kapacitor/v1.4/nodes/barrier_node/#cumulativesum), [Deadman](/kapacitor/v1.4/nodes/barrier_node/#deadman), [Default](/kapacitor/v1.4/nodes/barrier_node/#default), [Delete](/kapacitor/v1.4/nodes/barrier_node/#delete), [Derivative](/kapacitor/v1.4/nodes/barrier_node/#derivative), [Difference](/kapacitor/v1.4/nodes/barrier_node/#difference), [Distinct](/kapacitor/v1.4/nodes/barrier_node/#distinct), [Ec2Autoscale](/kapacitor/v1.4/nodes/barrier_node/#ec2autoscale), [Elapsed](/kapacitor/v1.4/nodes/barrier_node/#elapsed), [Eval](/kapacitor/v1.4/nodes/barrier_node/#eval), [First](/kapacitor/v1.4/nodes/barrier_node/#first), [Flatten](/kapacitor/v1.4/nodes/barrier_node/#flatten), [GroupBy](/kapacitor/v1.4/nodes/barrier_node/#groupby), [HoltWinters](/kapacitor/v1.4/nodes/barrier_node/#holtwinters), [HoltWintersWithFit](/kapacitor/v1.4/nodes/barrier_node/#holtwinterswithfit), [HttpOut](/kapacitor/v1.4/nodes/barrier_node/#httpout), [HttpPost](/kapacitor/v1.4/nodes/barrier_node/#httppost), [InfluxDBOut](/kapacitor/v1.4/nodes/barrier_node/#influxdbout), [Join](/kapacitor/v1.4/nodes/barrier_node/#join), [K8sAutoscale](/kapacitor/v1.4/nodes/barrier_node/#k8sautoscale), [KapacitorLoopback](/kapacitor/v1.4/nodes/barrier_node/#kapacitorloopback), [Last](/kapacitor/v1.4/nodes/barrier_node/#last), [Log](/kapacitor/v1.4/nodes/barrier_node/#log), [Max](/kapacitor/v1.4/nodes/barrier_node/#max), [Mean](/kapacitor/v1.4/nodes/barrier_node/#mean), [Median](/kapacitor/v1.4/nodes/barrier_node/#median), [Min](/kapacitor/v1.4/nodes/barrier_node/#min), [Mode](/kapacitor/v1.4/nodes/barrier_node/#mode), [MovingAverage](/kapacitor/v1.4/nodes/barrier_node/#movingaverage), [Percentile](/kapacitor/v1.4/nodes/barrier_node/#percentile), [Sample](/kapacitor/v1.4/nodes/barrier_node/#sample), [Shift](/kapacitor/v1.4/nodes/barrier_node/#shift), [Sideload](/kapacitor/v1.4/nodes/barrier_node/#sideload), [Spread](/kapacitor/v1.4/nodes/barrier_node/#spread), [StateCount](/kapacitor/v1.4/nodes/barrier_node/#statecount), [StateDuration](/kapacitor/v1.4/nodes/barrier_node/#stateduration), [Stats](/kapacitor/v1.4/nodes/barrier_node/#stats), [Stddev](/kapacitor/v1.4/nodes/barrier_node/#stddev), [Sum](/kapacitor/v1.4/nodes/barrier_node/#sum), [SwarmAutoscale](/kapacitor/v1.4/nodes/barrier_node/#swarmautoscale), [Top](/kapacitor/v1.4/nodes/barrier_node/#top), [Union](/kapacitor/v1.4/nodes/barrier_node/#union), [Where](/kapacitor/v1.4/nodes/barrier_node/#where), [Window](/kapacitor/v1.4/nodes/barrier_node/#window)
<a id='descr'/><hr/><br/>
### Description

A [BarrierNode](/kapacitor/v1.4/nodes/barrier_node/) will emit a barrier with the current time, according to the system
clock. Since the [BarrierNode](/kapacitor/v1.4/nodes/barrier_node/) emits based on system time, it allows pipelines to be
forced in the absence of data traffic. The barrier emitted will be based on either
idle time since the last received message or on a periodic timer based on the system
clock. Any messages received after an emitted barrier that is older than the last
emitted barrier will be dropped.

Example:


```js
stream
  |barrier()
    .idle(11s) // Must be longer than the window period
  |window()
    .period(10s)
    .every(5s)
  |top(10, 'value')
  //Post the top 10 results over the last 10s updated every 5s.
  |httpPost('http://example.com/api/top10')
```



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Properties
----------

Property methods modify state on the calling node.
They do not add another node to the pipeline, and always return a reference to the calling node.
Property methods are marked using the `.` operator.


### Idle

Emit barrier based on idle time since the last received message.
Must be greater than zero **and longer than the associated window `period`**.


```javascript
barrier.idle(value time.Duration)
```

{{% warn %}}
#### Barrier idle time and window period
`idle` must be greater than `period` of the associated [window](/kapacitor/v1.4/nodes/window_node/).
If `idle` times are less than the window `period`, data may be lost.
{{% /warn %}}

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### Period

Emit barrier based on periodic timer. The timer is based on system
clock rather than message time.
Must be greater than zero.


```javascript
barrier.period(value time.Duration)
```

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Chaining Methods
----------------

Chaining methods create a new node in the pipeline as a child of the calling node.
They do not modify the calling node.
Chaining methods are marked using the `|` operator.


### Alert

Create an alert node, which can trigger alerts.


```javascript
barrier|alert()
```

Returns: [AlertNode](/kapacitor/v1.4/nodes/alert_node/)

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### Barrier

Create a new Barrier node that emits a BarrierMessage periodically

One BarrierMessage will be emitted every period duration


```javascript
barrier|barrier()
```

Returns: [BarrierNode](/kapacitor/v1.4/nodes/barrier_node/)

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### Bottom

Select the bottom `num` points for `field` and sort by any extra tags or fields.


```javascript
barrier|bottom(num int64, field string, fieldsAndTags ...string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Combine

Combine this node with itself. The data is combined on timestamp.


```javascript
barrier|combine(expressions ...ast.LambdaNode)
```

Returns: [CombineNode](/kapacitor/v1.4/nodes/combine_node/)

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### Count

Count the number of points.


```javascript
barrier|count(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### CumulativeSum

Compute a cumulative sum of each point that is received.
A point is emitted for every point collected.


```javascript
barrier|cumulativeSum(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Deadman

Helper function for creating an alert on low throughput, a.k.a. deadman's switch.

- Threshold -- trigger alert if throughput drops below threshold in points/interval.
- Interval -- how often to check the throughput.
- Expressions -- optional list of expressions to also evaluate. Useful for time of day alerting.

Example:


```javascript
    var data = stream
        |from()...
    // Trigger critical alert if the throughput drops below 100 points per 10s and checked every 10s.
    data
        |deadman(100.0, 10s)
    //Do normal processing of data
    data...
```

The above is equivalent to this
Example:


```javascript
    var data = stream
        |from()...
    // Trigger critical alert if the throughput drops below 100 points per 10s and checked every 10s.
    data
        |stats(10s)
            .align()
        |derivative('emitted')
            .unit(10s)
            .nonNegative()
        |alert()
            .id('node \'stream0\' in task \'{{ .TaskName }}\'')
            .message('{{ .ID }} is {{ if eq .Level "OK" }}alive{{ else }}dead{{ end }}: {{ index .Fields "emitted" | printf "%0.3f" }} points/10s.')
            .crit(lambda: "emitted" <= 100.0)
    //Do normal processing of data
    data...
```

The `id` and `message` alert properties can be configured globally via the 'deadman' configuration section.

Since the [AlertNode](/kapacitor/v1.4/nodes/alert_node/) is the last piece it can be further modified as usual.
Example:


```javascript
    var data = stream
        |from()...
    // Trigger critical alert if the throughput drops below 100 points per 10s and checked every 10s.
    data
        |deadman(100.0, 10s)
            .slack()
            .channel('#dead_tasks')
    //Do normal processing of data
    data...
```

You can specify additional lambda expressions to further constrain when the deadman's switch is triggered.
Example:


```javascript
    var data = stream
        |from()...
    // Trigger critical alert if the throughput drops below 100 points per 10s and checked every 10s.
    // Only trigger the alert if the time of day is between 8am-5pm.
    data
        |deadman(100.0, 10s, lambda: hour("time") >= 8 AND hour("time") <= 17)
    //Do normal processing of data
    data...
```



```javascript
barrier|deadman(threshold float64, interval time.Duration, expr ...ast.LambdaNode)
```

Returns: [AlertNode](/kapacitor/v1.4/nodes/alert_node/)

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### Default

Create a node that can set defaults for missing tags or fields.


```javascript
barrier|default()
```

Returns: [DefaultNode](/kapacitor/v1.4/nodes/default_node/)

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### Delete

Create a node that can delete tags or fields.


```javascript
barrier|delete()
```

Returns: [DeleteNode](/kapacitor/v1.4/nodes/delete_node/)

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### Derivative

Create a new node that computes the derivative of adjacent points.


```javascript
barrier|derivative(field string)
```

Returns: [DerivativeNode](/kapacitor/v1.4/nodes/derivative_node/)

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### Difference

Compute the difference between points independent of elapsed time.


```javascript
barrier|difference(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Distinct

Produce batch of only the distinct points.


```javascript
barrier|distinct(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Ec2Autoscale

Create a node that can trigger autoscale events for a ec2 autoscalegroup.


```javascript
barrier|ec2Autoscale()
```

Returns: [Ec2AutoscaleNode](/kapacitor/v1.4/nodes/ec2_autoscale_node/)

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### Elapsed

Compute the elapsed time between points


```javascript
barrier|elapsed(field string, unit time.Duration)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Eval

Create an eval node that will evaluate the given transformation function to each data point.
A list of expressions may be provided and will be evaluated in the order they are given.
The results are available to later expressions.


```javascript
barrier|eval(expressions ...ast.LambdaNode)
```

Returns: [EvalNode](/kapacitor/v1.4/nodes/eval_node/)

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### First

Select the first point.


```javascript
barrier|first(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Flatten

Flatten points with similar times into a single point.


```javascript
barrier|flatten()
```

Returns: [FlattenNode](/kapacitor/v1.4/nodes/flatten_node/)

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### GroupBy

Group the data by a set of tags.

Can pass literal * to group by all dimensions.
Example:


```javascript
    |groupBy(*)
```



```javascript
barrier|groupBy(tag ...interface{})
```

Returns: [GroupByNode](/kapacitor/v1.4/nodes/group_by_node/)

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### HoltWinters

Compute the holt-winters (/{{< latest "influxdb" "v1" >}}/query_language/functions/#holt-winters) forecast of a data set.


```javascript
barrier|holtWinters(field string, h int64, m int64, interval time.Duration)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### HoltWintersWithFit

Compute the holt-winters (/{{< latest "influxdb" "v1" >}}/query_language/functions/#holt-winters) forecast of a data set.
This method also outputs all the points used to fit the data in addition to the forecasted data.


```javascript
barrier|holtWintersWithFit(field string, h int64, m int64, interval time.Duration)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### HttpOut

Create an HTTP output node that caches the most recent data it has received.
The cached data is available at the given endpoint.
The endpoint is the relative path from the API endpoint of the running task.
For example, if the task endpoint is at `/kapacitor/v1/tasks/<task_id>` and endpoint is
`top10`, then the data can be requested from `/kapacitor/v1/tasks/<task_id>/top10`.


```javascript
barrier|httpOut(endpoint string)
```

Returns: [HTTPOutNode](/kapacitor/v1.4/nodes/http_out_node/)

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### HttpPost

Creates an HTTP Post node that POSTS received data to the provided HTTP endpoint.
HttpPost expects 0 or 1 arguments. If 0 arguments are provided, you must specify an
endpoint property method.


```javascript
barrier|httpPost(url ...string)
```

Returns: [HTTPPostNode](/kapacitor/v1.4/nodes/http_post_node/)

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### InfluxDBOut

Create an influxdb output node that will store the incoming data into InfluxDB.


```javascript
barrier|influxDBOut()
```

Returns: [InfluxDBOutNode](/kapacitor/v1.4/nodes/influx_d_b_out_node/)

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### Join

Join this node with other nodes. The data is joined on timestamp.


```javascript
barrier|join(others ...Node)
```

Returns: [JoinNode](/kapacitor/v1.4/nodes/join_node/)

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### K8sAutoscale

Create a node that can trigger autoscale events for a kubernetes cluster.


```javascript
barrier|k8sAutoscale()
```

Returns: [K8sAutoscaleNode](/kapacitor/v1.4/nodes/k8s_autoscale_node/)

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### KapacitorLoopback

Create an kapacitor loopback node that will send data back into Kapacitor as a stream.


```javascript
barrier|kapacitorLoopback()
```

Returns: [KapacitorLoopbackNode](/kapacitor/v1.4/nodes/kapacitor_loopback_node/)

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### Last

Select the last point.


```javascript
barrier|last(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Log

Create a node that logs all data it receives.


```javascript
barrier|log()
```

Returns: [LogNode](/kapacitor/v1.4/nodes/log_node/)

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### Max

Select the maximum point.


```javascript
barrier|max(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Mean

Compute the mean of the data.


```javascript
barrier|mean(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Median

Compute the median of the data. Note, this method is not a selector,
if you want the median point use `.percentile(field, 50.0)`.


```javascript
barrier|median(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Min

Select the minimum point.


```javascript
barrier|min(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Mode

Compute the mode of the data.


```javascript
barrier|mode(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### MovingAverage

Compute a moving average of the last window points.
No points are emitted until the window is full.


```javascript
barrier|movingAverage(field string, window int64)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Percentile

Select a point at the given percentile. This is a selector function, no interpolation between points is performed.


```javascript
barrier|percentile(field string, percentile float64)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Sample

Create a new node that samples the incoming points or batches.

One point will be emitted every count or duration specified.


```javascript
barrier|sample(rate interface{})
```

Returns: [SampleNode](/kapacitor/v1.4/nodes/sample_node/)

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### Shift

Create a new node that shifts the incoming points or batches in time.


```javascript
barrier|shift(shift time.Duration)
```

Returns: [ShiftNode](/kapacitor/v1.4/nodes/shift_node/)

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### Sideload

Create a node that can load data from external sources


```javascript
barrier|sideload()
```

Returns: [SideloadNode](/kapacitor/v1.4/nodes/sideload_node/)

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### Spread

Compute the difference between `min` and `max` points.


```javascript
barrier|spread(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### StateCount

Create a node that tracks number of consecutive points in a given state.


```javascript
barrier|stateCount(expression ast.LambdaNode)
```

Returns: [StateCountNode](/kapacitor/v1.4/nodes/state_count_node/)

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### StateDuration

Create a node that tracks duration in a given state.


```javascript
barrier|stateDuration(expression ast.LambdaNode)
```

Returns: [StateDurationNode](/kapacitor/v1.4/nodes/state_duration_node/)

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### Stats

Create a new stream of data that contains the internal statistics of the node.
The interval represents how often to emit the statistics based on real time.
This means the interval time is independent of the times of the data points the source node is receiving.


```javascript
barrier|stats(interval time.Duration)
```

Returns: [StatsNode](/kapacitor/v1.4/nodes/stats_node/)

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### Stddev

Compute the standard deviation.


```javascript
barrier|stddev(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Sum

Compute the sum of all values.


```javascript
barrier|sum(field string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### SwarmAutoscale

Create a node that can trigger autoscale events for a docker swarm cluster.


```javascript
barrier|swarmAutoscale()
```

Returns: [SwarmAutoscaleNode](/kapacitor/v1.4/nodes/swarm_autoscale_node/)

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### Top

Select the top `num` points for `field` and sort by any extra tags or fields.


```javascript
barrier|top(num int64, field string, fieldsAndTags ...string)
```

Returns: [InfluxQLNode](/kapacitor/v1.4/nodes/influx_q_l_node/)

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### Union

Perform the union of this node and all other given nodes.


```javascript
barrier|union(node ...Node)
```

Returns: [UnionNode](/kapacitor/v1.4/nodes/union_node/)

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### Where

Create a new node that filters the data stream by a given expression.


```javascript
barrier|where(expression ast.LambdaNode)
```

Returns: [WhereNode](/kapacitor/v1.4/nodes/where_node/)

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### Window

Create a new node that windows the stream by time.

NOTE: Window can only be applied to stream edges.


```javascript
barrier|window()
```

Returns: [WindowNode](/kapacitor/v1.4/nodes/window_node/)

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