monitor.deadman() function

monitor.deadman() detects when a group stops reporting data. It takes a stream of tables and reports if groups have been observed since time t.

monitor.deadman() retains the most recent row from each input table and adds a dead column. If a record appears after time t, monitor.deadman() sets dead to false. Otherwise, dead is set to true.

Function type signature

(<-tables: stream[{B with _time: C}], t: A) => stream[{B with dead: bool, _time: C}] where A: Comparable, C: Comparable

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Parameters

t

({{< req >}}) Time threshold for the deadman check.

tables

Input data. Default is piped-forward data (<-).

Examples

• Detect if a host hasn’t reported since a specific time
• Detect if a host hasn't reported since a relative time

Detect if a host hasn’t reported since a specific time

import "array"
import "influxdata/influxdb/monitor"

data =
    array.from(
        rows: [
            {_time: 2021-01-01T00:00:00Z, host: "a", _value: 1.2},
            {_time: 2021-01-01T00:01:00Z, host: "a", _value: 1.3},
            {_time: 2021-01-01T00:02:00Z, host: "a", _value: 1.4},
            {_time: 2021-01-01T00:03:00Z, host: "a", _value: 1.3},
        ],
    )
        |> group(columns: ["host"])

data
    |> monitor.deadman(t: 2021-01-01T00:05:00Z)

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Input data

Output data

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Detect if a host hasn't reported since a relative time

Use date.add() to return a time value relative to a specified time.

import "influxdata/influxdb/monitor"
import "date"

from(bucket: "example-bucket")
    |> range(start: -10m)
    |> filter(fn: (r) => r._measurement == "example-measurement")
    |> monitor.deadman(t: date.add(d: -5m, to: now()))