docs-v2/content/influxdb/cloud/reference/flux/stdlib/monitor/check.md

title	description	aliases	menu	weight
monitor.check() function	The `monitor.check()` function checks input data and assigns a level (`ok`, `info`, `warn`, or `crit`) to each row based on predicate functions.	/influxdb/cloud/reference/flux/functions/monitor/check/	influxdb_cloud_ref name parent monitor.check InfluxDB monitor	202

The monitor.check() function checks input data and assigns a level (ok, info, warn, or crit) to each row based on predicate functions.

Function type: Transformation

import "influxdata/influxdb/monitor"

monitor.check(
  crit: (r) => r._value > 90.0,
  warn: (r) => r._value > 80.0,
  info: (r) => r._value > 60.0,
  ok:   (r) => r._value <= 20.0,
  messageFn: (r) => "The current level is ${r._level}",
  data: {}
)

monitor.check() stores statuses in the _level column and writes results to the statuses measurement in the _monitoring bucket.

Parameters

crit

Predicate function that determines crit status. Default is (r) => false.

Data type: Function

warn

Predicate function that determines warn status. Default is (r) => false.

Data type: Function

info

Predicate function that determines info status. Default is (r) => false.

Data type: Function

ok

Predicate function that determines ok status. Default is (r) => true.

Data type: Function

messageFn

A function that constructs a message to append to each row. The message is stored in the _message column.

Data type: Function

data

Metadata used to identify this check and append tags to each row.

Data type: Record

The data record should contain the following fields:

• _check_id: check ID
• _check_name: check name
• _type: check type (threshold, deadman, or custom)
• tags: tags to append to each checked record (for example: {foo: "bar", baz: "quz"})

The InfluxDB monitoring and alerting system uses monitor.check() to store information about checks and automatically assigns the _check_id and _check_name values. If writing a custom check task, we recommend using unique arbitrary values for _check_id and _check_name.

Examples

Monitor disk usage

import "influxdata/influxdb/monitor"

from(bucket: "telegraf")
  |> range(start: -1h)
  |> filter(fn: (r) =>
      r._measurement == "disk" and
      r._field == "used_percent"
  )
  |> group(columns: ["_measurement"])
  |> monitor.check(
    crit: (r) => r._value > 90.0,
    warn: (r) => r._value > 80.0,
    info: (r) => r._value > 70.0,
    ok:   (r) => r._value <= 60.0,
    messageFn: (r) =>
      if r._level == "crit" then "Critical alert!! Disk usage is at ${r._value}%!"
      else if r._level == "warn" then "Warning! Disk usage is at ${r._value}%."
      else if r._level == "info" then "Disk usage is at ${r._value}%."
      else "Things are looking good.",
    data: {
      _check_name: "Disk Utilization (Used Percentage)",
      _check_id: "disk_used_percent",
      _type: "threshold",
      tags: {}
    }
  )