Kapacitor contents

FromNode

This is archived documentation for InfluxData product versions that are no longer maintained. For newer documentation, see the latest InfluxData documentation.

A FromNode selects a subset of the data flowing through a StreamNode. The stream node allows you to select which portion of the stream you want to process.

Example:

    stream
        |from()
           .database('mydb')
           .retentionPolicy('myrp')
           .measurement('mymeasurement')
           .where(lambda: "host" =~ /logger\d+/)
        |window()
        ...

The above example selects only data points from the database mydb and retention policy myrp and measurement mymeasurement where the tag host matches the regex logger\d+

Index

Properties

Chaining Methods

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.

Database

The database name. If empty any database will be used.

node.database(value string)

GroupBy

Group the data by a set of tags.

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

  stream
      |from()
          .groupBy(*)

node.groupBy(tag ...interface{})

GroupByMeasurement

If set will include the measurement name in the group ID. Along with any other group by dimensions.

Example:

 stream
      |from()
          .database('mydb')
          .groupByMeasurement()
          .groupBy('host')

The above example selects all measurements from the database 'mydb' and then each point is grouped by the host tag and measurement name. Thus keeping measurements in their own groups.

node.groupByMeasurement()

Measurement

The measurement name If empty any measurement will be used.

node.measurement(value string)

RetentionPolicy

The retention policy name If empty any retention policy will be used.

node.retentionPolicy(value string)

Round

Optional duration for rounding timestamps. Helpful to ensure data points land on specific boundaries Example:

    stream
       |from()
           .measurement('mydata')
           .round(1s)

All incoming data will be rounded to the nearest 1 second boundary.

node.round(value time.Duration)

Truncate

Optional duration for truncating timestamps. Helpful to ensure data points land on specific boundaries Example:

    stream
       |from()
           .measurement('mydata')
           .truncate(1s)

All incoming data will be truncated to 1 second resolution.

node.truncate(value time.Duration)

Where

Filter the current stream using the given expression. This expression is a Kapacitor expression. Kapacitor expressions are a superset of InfluxQL WHERE expressions. See the expression docs for more information.

Multiple calls to the Where method will AND together each expression.

Example:

    stream
       |from()
          .where(lambda: condition1)
          .where(lambda: condition2)

The above is equivalent to this Example:

    stream
       |from()
          .where(lambda: condition1 AND condition2)

NOTE: Becareful to always use |from if you want multiple different streams.

Example:

  var data = stream
      |from()
          .measurement('cpu')
  var total = data
      .where(lambda: "cpu" == 'cpu-total')
  var others = data
      .where(lambda: "cpu" != 'cpu-total')

The example above is equivalent to the example below, which is obviously not what was intended.

Example:

  var data = stream
      |from()
          .measurement('cpu')
          .where(lambda: "cpu" == 'cpu-total' AND "cpu" != 'cpu-total')
  var total = data
  var others = total

The example below will create two different streams each selecting a different subset of the original stream.

Example:

  var data = stream
      |from()
          .measurement('cpu')
  var total = stream
      |from()
          .measurement('cpu')
          .where(lambda: "cpu" == 'cpu-total')
  var others = stream
      |from()
          .measurement('cpu')
          .where(lambda: "cpu" != 'cpu-total')

If empty then all data points are considered to match.

node.where(lambda ast.LambdaNode)

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.

node|alert()

Returns: AlertNode

Bottom

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

node|bottom(num int64, field string, fieldsAndTags ...string)

Returns: InfluxQLNode

Combine

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

node|combine(expressions ...ast.LambdaNode)

Returns: CombineNode

Count

Count the number of points.

node|count(field string)

Returns: InfluxQLNode

CumulativeSum

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

node|cumulativeSum(field string)

Returns: InfluxQLNode

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:

    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:

    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 is the last piece it can be further modified as usual. Example:

    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:

    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...

node|deadman(threshold float64, interval time.Duration, expr ...ast.LambdaNode)

Returns: AlertNode

Default

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

node|default()

Returns: DefaultNode

Delete

Create a node that can delete tags or fields.

node|delete()

Returns: DeleteNode

Derivative

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

node|derivative(field string)

Returns: DerivativeNode

Difference

Compute the difference between points independent of elapsed time.

node|difference(field string)

Returns: InfluxQLNode

Distinct

Produce batch of only the distinct points.

node|distinct(field string)

Returns: InfluxQLNode

Elapsed

Compute the elapsed time between points

node|elapsed(field string, unit time.Duration)

Returns: InfluxQLNode

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.

node|eval(expressions ...ast.LambdaNode)

Returns: EvalNode

First

Select the first point.

node|first(field string)

Returns: InfluxQLNode

Flatten

Flatten points with similar times into a single point.

node|flatten()

Returns: FlattenNode

From

Creates a new stream node that can be further filtered using the Database, RetentionPolicy, Measurement and Where properties. From can be called multiple times to create multiple independent forks of the data stream.

Example:

    // Select the 'cpu' measurement from just the database 'mydb'
    // and retention policy 'myrp'.
    var cpu = stream
        |from()
            .database('mydb')
            .retentionPolicy('myrp')
            .measurement('cpu')
    // Select the 'load' measurement from any database and retention policy.
    var load = stream
        |from()
            .measurement('load')
    // Join cpu and load streams and do further processing.
    cpu
        |join(load)
            .as('cpu', 'load')
        ...

node|from()

Returns: FromNode

HoltWinters

Compute the holt-winters forecast of a data set.

node|holtWinters(field string, h int64, m int64, interval time.Duration)

Returns: InfluxQLNode

HoltWintersWithFit

Compute the 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.

node|holtWintersWithFit(field string, h int64, m int64, interval time.Duration)

Returns: InfluxQLNode

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/&lt;task_id&gt; and endpoint is top10, then the data can be requested from /kapacitor/v1/tasks/&lt;task_id&gt;/top10.

node|httpOut(endpoint string)

Returns: HTTPOutNode

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.

node|httpPost(url ...string)

Returns: HTTPPostNode

InfluxDBOut

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

node|influxDBOut()

Returns: InfluxDBOutNode

Join

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

node|join(others ...Node)

Returns: JoinNode

K8sAutoscale

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

node|k8sAutoscale()

Returns: K8sAutoscaleNode

KapacitorLoopback

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

node|kapacitorLoopback()

Returns: KapacitorLoopbackNode

Last

Select the last point.

node|last(field string)

Returns: InfluxQLNode

Log

Create a node that logs all data it receives.

node|log()

Returns: LogNode

Max

Select the maximum point.

node|max(field string)

Returns: InfluxQLNode

Mean

Compute the mean of the data.

node|mean(field string)

Returns: InfluxQLNode

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).

node|median(field string)

Returns: InfluxQLNode

Min

Select the minimum point.

node|min(field string)

Returns: InfluxQLNode

Mode

Compute the mode of the data.

node|mode(field string)

Returns: InfluxQLNode

MovingAverage

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

node|movingAverage(field string, window int64)

Returns: InfluxQLNode

Percentile

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

node|percentile(field string, percentile float64)

Returns: InfluxQLNode

Sample

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

One point will be emitted every count or duration specified.

node|sample(rate interface{})

Returns: SampleNode

Shift

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

node|shift(shift time.Duration)

Returns: ShiftNode

Spread

Compute the difference between min and max points.

node|spread(field string)

Returns: InfluxQLNode

StateCount

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

node|stateCount(expression ast.LambdaNode)

Returns: StateCountNode

StateDuration

Create a node that tracks duration in a given state.

node|stateDuration(expression ast.LambdaNode)

Returns: StateDurationNode

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.

node|stats(interval time.Duration)

Returns: StatsNode

Stddev

Compute the standard deviation.

node|stddev(field string)

Returns: InfluxQLNode

Sum

Compute the sum of all values.

node|sum(field string)

Returns: InfluxQLNode

Top

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

node|top(num int64, field string, fieldsAndTags ...string)

Returns: InfluxQLNode

Union

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

node|union(node ...Node)

Returns: UnionNode

Window

Create a new node that windows the stream by time.

NOTE: Window can only be applied to stream edges.

node|window()

Returns: WindowNode