---
title: monitor.deadman() function
description: >
  `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`.
menu:
  flux_v0_ref:
    name: monitor.deadman
    parent: influxdata/influxdb/monitor
    identifier: influxdata/influxdb/monitor/deadman
weight: 301
flux/v0/tags: [transformations]
---

<!------------------------------------------------------------------------------

IMPORTANT: This page was generated from comments in the Flux source code. Any
edits made directly to this page will be overwritten the next time the
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To make updates to this documentation, update the function comments above the
function definition in the Flux source code:

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Contributing to Flux: https://github.com/influxdata/flux#contributing
Fluxdoc syntax: https://github.com/influxdata/flux/blob/master/docs/fluxdoc.md

------------------------------------------------------------------------------->

`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

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

{{% caption %}}
For more information, see [Function type signatures](/flux/v0/function-type-signatures/).
{{% /caption %}}

## 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-hasnt-reported-since-a-specific-time)
- [Detect if a host hasn't reported since a relative time](#detect-if-a-host-hasnt-reported-since-a-relative-time)

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

```js
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)

```

{{< expand-wrapper >}}
{{% expand "View example input and output" %}}

#### Input data

| _time                | *host | _value  |
| -------------------- | ----- | ------- |
| 2021-01-01T00:00:00Z | a     | 1.2     |
| 2021-01-01T00:01:00Z | a     | 1.3     |
| 2021-01-01T00:02:00Z | a     | 1.4     |
| 2021-01-01T00:03:00Z | a     | 1.3     |


#### Output data

| _time                | _value  | dead  | *host |
| -------------------- | ------- | ----- | ----- |
| 2021-01-01T00:03:00Z | 1.3     | true  | a     |

{{% /expand %}}
{{< /expand-wrapper >}}

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

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

```js
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()))

```