docs-v2/content/kapacitor/v1/reference/nodes/combine_node.md

---
title: CombineNode
description: >
  CombineNode combines data from a single node with itself. Points with the same time are grouped and then combinations are created. The size of the combinations is defined by how many expressions are given.
note: Auto generated by tickdoc
menu:
  kapacitor_v1:
    name: CombineNode
    identifier: combine_node
    weight: 100
    parent: nodes
aliases:
  - /kapacitor/v1/nodes/combine_node/
---

The `combine` node combines data from a single node with itself.
Points with the same time are grouped and then combinations are created.
The size of the combinations is defined by how many expressions are given.
Combinations are order-independent and will never include the same point multiple times.

In the following example, data points for the `login` service are combined with
the data points from all other services:

```js
stream
  |from()
    .measurement('request_latency')
  |combine(lambda: "service" == 'login', lambda: TRUE)
    .as('login', 'other')
    // points that are within 1 second are considered the same time.
    .tolerance(1s)
    // delimiter for new field and tag names
    .delimiter('.')
  // Change group by to be new other.service tag
  |groupBy('other.service')
  // Both the "value" fields from each data point have been prefixed
  // with the respective names 'login' and 'other'.
  |eval(lambda: "login.value" / "other.value")
    .as('ratio')
  ...
```

In the following example, all combination pairs are created:

```js
|combine(lambda: TRUE, lambda: TRUE)
  .as('login', 'other')
```

In the following example, all combinations triples are created:

```js
|combine(lambda: TRUE, lambda: TRUE, lambda: TRUE)
  .as('login', 'other', 'another')
```


### Constructor

| Chaining Method | Description |
|:---------|:---------|
| **combine ( `expressions` `...ast.LambdaNode`)** | Combine this node with itself. The data is combined on timestamp.  |

### Property Methods

| Setters | Description |
|:---|:---|
| **[as](#as) ( `names` `...string`)** | Prefix names for all fields from the respective nodes. Each field from the parent nodes will be prefixed with the provided name and a '.'. See the example above.  |
| **[delimiter](#delimiter) ( `value` `string`)** | The delimiter between the As names and existing field an tag keys. Can be the empty string, but you are responsible for ensuring conflicts are not possible if you use the empty string.  |
| **[max](#max) ( `value` `int64`)** | Maximum number of possible combinations. Since the number of possible combinations can grow very rapidly you can set a maximum number of combinations allowed. If the max is crossed, an error is logged and the combinations are not calculated. Default: 10,000  |
| **[quiet](#quiet) ( )** | Suppress all error logging events from this node. |
| **[tolerance](#tolerance) ( `value` `time.Duration`)** | The maximum duration of time that two incoming points can be apart and still be considered to be equal in time. The joined data point's time will be rounded to the nearest multiple of the tolerance duration.  |



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

---

## 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.


### As

Prefix names for all fields from the respective nodes.
Each field from the parent nodes will be prefixed with the provided name and a `.`.
See the example above.

The names cannot have a dot `.` character.



```js
combine.as(names ...string)
```


### Delimiter

The delimiter between the As names and existing field an tag keys.
Can be the empty string, but you are responsible for ensuring conflicts are not possible if you use the empty string.


```js
combine.delimiter(value string)
```


### Max

Maximum number of possible combinations.
Since the number of possible combinations can grow very rapidly,
you can set a maximum number of combinations allowed.
If the max is exceeded, an error is logged and the combinations are not calculated.

**Default:** 10,000


```js
combine.max(value int64)
```


### Quiet

Suppress all error logging events from this node.

```js
combine.quiet()
```


### Tolerance

The maximum duration of time that two incoming points
can be apart and still be considered to be equal in time.
The joined data point's time will be rounded to the nearest
multiple of the tolerance duration.


```js
combine.tolerance(value time.Duration)
```


## 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.


```js
combine|alert()
```

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

### Barrier

Create a new Barrier node that emits a BarrierMessage periodically.

One BarrierMessage will be emitted every period duration.


```js
combine|barrier()
```

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

### Bottom

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


```js
combine|bottom(num int64, field string, fieldsAndTags ...string)
```

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

### ChangeDetect

Create a new node that only emits new points if different from the previous point.

```js
combine|changeDetect(field string)
```

Returns: [ChangeDetectNode](/kapacitor/v1/reference/nodes/change_detect_node/)

### Combine

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


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

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

### Count

Count the number of points.


```js
combine|count(field string)
```

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

### CumulativeSum

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


```js
combine|cumulativeSum(field string)
```

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

### 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:


```js
    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:


```js
    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/reference/nodes/alert_node/) is the last piece it can be further modified as usual.
Example:


```js
    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:


```js
    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...
```



```js
combine|deadman(threshold float64, interval time.Duration, expr ...ast.LambdaNode)
```

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

### Default

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


```js
combine|default()
```

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

### Delete

Create a node that can delete tags or fields.


```js
combine|delete()
```

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

### Derivative

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


```js
combine|derivative(field string)
```

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

### Difference

Compute the difference between points independent of elapsed time.


```js
combine|difference(field string)
```

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

### Distinct

Produce batch of only the distinct points.


```js
combine|distinct(field string)
```

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

### Ec2Autoscale

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


```js
combine|ec2Autoscale()
```

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

### Elapsed

Compute the elapsed time between points.


```js
combine|elapsed(field string, unit time.Duration)
```

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

### 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.


```js
combine|eval(expressions ...ast.LambdaNode)
```

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

### First

Select the first point.


```js
combine|first(field string)
```

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

### Flatten

Flatten points with similar times into a single point.


```js
combine|flatten()
```

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

### GroupBy

Group the data by a set of tags.

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


```js
    |groupBy(*)
```



```js
combine|groupBy(tag ...interface{})
```

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

### HoltWinters

Compute the Holt-Winters (/influxdb/v1/query_language/functions/#holt-winters) forecast of a data set.


```js
combine|holtWinters(field string, h int64, m int64, interval time.Duration)
```

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

### HoltWintersWithFit

Compute the Holt-Winters (/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.


```js
combine|holtWintersWithFit(field string, h int64, m int64, interval time.Duration)
```

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

### 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`.


```js
combine|httpOut(endpoint string)
```

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

### 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.


```js
combine|httpPost(url ...string)
```

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

### InfluxDBOut

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


```js
combine|influxDBOut()
```

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

### Join

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


```js
combine|join(others ...Node)
```

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

### K8sAutoscale

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


```js
combine|k8sAutoscale()
```

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

### KapacitorLoopback

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


```js
combine|kapacitorLoopback()
```

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

### Last

Select the last point.


```js
combine|last(field string)
```

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

### Log

Create a node that logs all data it receives.


```js
combine|log()
```

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

### Mean

Compute the mean of the data.


```js
combine|mean(field string)
```

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

### 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)`.


```js
combine|median(field string)
```

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

### Min

Select the minimum point.


```js
combine|min(field string)
```

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

### Mode

Compute the mode of the data.


```js
combine|mode(field string)
```

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

### MovingAverage

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


```js
combine|movingAverage(field string, window int64)
```

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

### Percentile

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


```js
combine|percentile(field string, percentile float64)
```

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

### Sample

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

One point will be emitted every count or duration specified.


```js
combine|sample(rate interface{})
```

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

### Shift

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


```js
combine|shift(shift time.Duration)
```

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

### Sideload

Create a node that can load data from external sources.


```js
combine|sideload()
```

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

### Spread

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


```js
combine|spread(field string)
```

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

### StateCount

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


```js
combine|stateCount(expression ast.LambdaNode)
```

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

### StateDuration

Create a node that tracks duration in a given state.


```js
combine|stateDuration(expression ast.LambdaNode)
```

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

### 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.


```js
combine|stats(interval time.Duration)
```

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

### Stddev

Compute the standard deviation.


```js
combine|stddev(field string)
```

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

### Sum

Compute the sum of all values.


```js
combine|sum(field string)
```

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

### SwarmAutoscale

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


```js
combine|swarmAutoscale()
```

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

### Top

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


```js
combine|top(num int64, field string, fieldsAndTags ...string)
```

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

### Trickle

Create a new node that converts batch data to stream data.

```js
combine|trickle()
```

Returns: [TrickleNode](/kapacitor/v1/reference/nodes/trickle_node/)

### Union

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


```js
combine|union(node ...Node)
```

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

### Where

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


```js
combine|where(expression ast.LambdaNode)
```

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

### Window

Create a new node that windows the stream by time.

NOTE: Window can only be applied to stream edges.


```js
combine|window()
```

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