---
title: Monitor states
seotitle: Monitor states and state changes in your events and metrics with Flux.
description: Flux provides several functions to help monitor states and state changes in your data.
menu:
  influxdb_v1:
    name: Monitor states
    parent: Query with Flux
weight: 20
canonical: /influxdb/v2/query-data/flux/monitor-states/
v2: /influxdb/v2/query-data/flux/monitor-states/
---

Flux helps you monitor states in your metrics and events:

- [Find how long a state persists](#find-how-long-a-state-persists)
- [Count the number of consecutive states](#count-the-number-of-consecutive-states)
- [Detect state changes](#example-query-to-count-machine-state)

If you're just getting started with Flux queries, check out the following:

- [Get started with Flux](/influxdb/v1/flux/get-started/) for a conceptual overview of Flux.
- [Execute queries](/influxdb/v1/flux/guides/executing-queries/) to discover a variety of ways to run your queries.

## Find how long a state persists

1. Use the [`stateDuration()`](/flux/v0/stdlib/universe/stateduration/) function to calculate how long a column value has remained the same value (or state). Include the following information:

    - **Column to search:** any tag key, tag value, field key, field value, or measurement.
    - **Value:** the value (or state) to search for in the specified column.
    - **State duration column:** a new column to store the state duration─the length of time that the specified value persists.
    - **Unit:** the unit of time (`1s` (by default), `1m`, `1h`) used to increment the state duration.

    <!-- -->
    ```js
    |> stateDuration(
      fn: (r) =>
      r._column_to_search == "value_to_search_for",
      column: "state_duration",
      unit: 1s
    )
    ```

2. Use `stateDuration()` to search each point for the specified value:

    - For the first point that evaluates `true`, the state duration is set to `0`. For each consecutive point that evaluates `true`, the state duration increases by the time interval between each consecutive point (in specified units).
    - If the state is `false`, the state duration is reset to `-1`.

### Example query with stateDuration()

The following query searches the `doors` bucket over the past 5 minutes to find how many seconds a door has been `closed`.

```js
from(bucket: "doors")
  |> range(start: -5m)
  |> stateDuration(
    fn: (r) =>
    r._value == "closed",
    column: "door_closed",
    unit: 1s
  )
```

In this example, `door_closed` is the **State duration** column. If you write data to the `doors` bucket every minute, the state duration increases by `60s` for each consecutive point where `_value` is `closed`. If `_value` is not `closed`, the state duration is reset to `0`.

#### Query results

Results for the example query above may look like this (for simplicity, we've omitted the measurement, tag, and field columns):

```bash
_time                   _value        door_closed
2019-10-26T17:39:16Z    closed        0
2019-10-26T17:40:16Z    closed        60
2019-10-26T17:41:16Z    closed        120
2019-10-26T17:42:16Z    open          -1
2019-10-26T17:43:16Z    closed        0
2019-10-26T17:44:27Z    closed        60
```

## Count the number of consecutive states

1. Use the `stateCount()` function and include the following information:

    - **Column to search:** any tag key, tag value, field key, field value, or measurement.
    - **Value:** to search for in the specified column.
    - **State count column:** a new column to store the state count─the number of consecutive records in which the specified value exists.

    <!--  -->
    ```js
    |> stateCount
       (fn: (r) =>
        r._column_to_search == "value_to_search_for",
        column: "state_count"
      )
    ```

2. Use `stateCount()` to search each point for the specified value:

    - For the first point that evaluates `true`, the state count is set to `1`. For each consecutive point that evaluates `true`, the state count increases by 1.
    - If the state is `false`, the state count is reset to `-1`.

### Example query with stateCount()

The following query searches the `doors` bucket over the past 5 minutes and
calculates how many points have `closed` as their `_value`.

```js
from(bucket: "doors")
  |> range(start: -5m)
  |> stateDuration(
    fn: (r) =>
    r._value == "closed",
    column: "door_closed")
```

This example stores the **state count** in the `door_closed` column.
If you write data to the `doors` bucket every minute, the state count increases
by `1` for each consecutive point where `_value` is `closed`.
If `_value` is not `closed`, the state count is reset to `-1`.

#### Query results

Results for the example query above may look like this (for simplicity, we've omitted the measurement, tag, and field columns):

```bash
_time                   _value        door_closed
2019-10-26T17:39:16Z    closed        1
2019-10-26T17:40:16Z    closed        2
2019-10-26T17:41:16Z    closed        3
2019-10-26T17:42:16Z    open          -1
2019-10-26T17:43:16Z    closed        1
2019-10-26T17:44:27Z    closed        2
```

#### Example query to count machine state

The following query checks the machine state every minute (idle, assigned, or busy).
InfluxDB searches the `servers` bucket over the past hour and counts records with a machine state of `idle`, `assigned` or `busy`.

```js
from(bucket: "servers")
  |> range(start: -1h)
  |> filter(fn: (r) =>
     r.machine_state == "idle" or
     r.machine_state == "assigned" or
     r.machine_state == "busy"
  )
  |> stateCount(fn: (r) => r.machine_state == "busy", column: "_count")
  |> stateCount(fn: (r) => r.machine_state == "assigned", column: "_count")
  |> stateCount(fn: (r) => r.machine_state == "idle", column: "_count")
```