---
title: UDFNode (Kapacitor TICKscript node)
description: UDFNode runs a user defined function (UDF) in a separate process.
note: Auto generated by tickdoc

menu:
  kapacitor_1_4:
    name: UDFNode
    identifier: u_d_f_node
    weight: 310
    parent: TICKscript nodes
---
### Constructor

| Chaining Method | Description |
|:---------|:---------|
| **[uDF](#descr)** | Has no constructor signature. |
### Property Methods

| Setters | Description |
|:---|:---|
| **[uDFName](#udfname) ( `value` `string`)** |  |



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

A [UDFNode](/kapacitor/v1.4/nodes/u_d_f_node/) is a node that can run a User Defined Function (UDF) in a separate process.

A UDF is a custom script or binary that can communicate via Kapacitor's UDF RPC protocol.
The path and arguments to the UDF program are specified in Kapacitor's configuration.
Using TICKscripts you can invoke and configure your UDF for each task.

See the [README.md](https://github.com/influxdata/kapacitor/tree/master/udf/agent/)
for details on how to write your own UDF.

UDFs are configured via Kapacitor's main configuration file.

Example:


```javascript
    [udf]
    [udf.functions]
        # Example moving average UDF.
        [udf.functions.movingAverage]
            prog = "/path/to/executable/moving_avg"
            args = []
            timeout = "10s"
```

UDFs are first class objects in TICKscripts and are referenced via their configuration name.

Example:


```javascript
     // Given you have a UDF that computes a moving average
     // The UDF can define what its options are and then can be
     // invoked via a TICKscript like so:
     stream
         |from()...
         @movingAverage()
             .field('value')
             .size(100)
             .as('mavg')
         |httpOut('movingaverage')
```

NOTE: The UDF process runs as the same user as the Kapacitor daemon.
As a result, make sure the user is properly secured, as well as the configuration file.


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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.


### UDFName

```javascript
uDF.uDFName(value string)
```

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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
uDF|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
uDF|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
uDF|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
uDF|combine(expressions ...ast.LambdaNode)
```

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

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### Count

Count the number of points.


```javascript
uDF|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
uDF|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
uDF|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
uDF|default()
```

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

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### Delete

Create a node that can delete tags or fields.


```javascript
uDF|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
uDF|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
uDF|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
uDF|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
uDF|ec2Autoscale()
```

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

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### Elapsed

Compute the elapsed time between points


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

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

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### First

Select the first point.


```javascript
uDF|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
uDF|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
uDF|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
uDF|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
uDF|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
uDF|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
uDF|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
uDF|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
uDF|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
uDF|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
uDF|kapacitorLoopback()
```

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

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### Last

Select the last point.


```javascript
uDF|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
uDF|log()
```

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

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### Max

Select the maximum point.


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

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

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### Min

Select the minimum point.


```javascript
uDF|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
uDF|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
uDF|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
uDF|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
uDF|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
uDF|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
uDF|sideload()
```

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

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### Spread

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


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

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

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### Stddev

Compute the standard deviation.


```javascript
uDF|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
uDF|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
uDF|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
uDF|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
uDF|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
uDF|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
uDF|window()
```

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

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