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---
description: "Metrics plugins."
keywords: "Examples, Usage, plugins, docker, documentation, user guide, metrics"
---
<!-- This file is maintained within the docker/cli GitHub
repository at https://github.com/docker/cli/. Make all
pull requests against that repo. If you see this file in
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# Docker metrics collector plugins
Docker exposes internal metrics based on the prometheus format. Metrics plugins
enable accessing these metrics in a consistent way by providing a Unix
socket at a predefined path where the plugin can scrape the metrics.
> **Note**
>
> While the plugin interface for metrics is non-experimental, the naming of the
> metrics and metric labels is still considered experimental and may change in a
> future version.
## Creating a metrics plugin
You must currently set `PropagatedMount` in the plugin `config.json` to
`/run/docker`. This allows the plugin to receive updated mounts
(the bind-mounted socket) from Docker after the plugin is already configured.
## MetricsCollector protocol
Metrics plugins must register as implementing the`MetricsCollector` interface
in `config.json`.
On Unix platforms, the socket is located at `/run/docker/metrics.sock` in the
plugin's rootfs.
`MetricsCollector` must implement two endpoints:
### `MetricsCollector.StartMetrics`
Signals to the plugin that the metrics socket is now available for scraping
**Request**
```json
{}
```
The request has no playload.
**Response**
```json
{
"Err": ""
}
```
If an error occurred during this request, add an error message to the `Err` field
in the response. If no error then you can either send an empty response (`{}`)
or an empty value for the `Err` field. Errors will only be logged.
### `MetricsCollector.StopMetrics`
Signals to the plugin that the metrics socket is no longer available.
This may happen when the daemon is shutting down.
**Request**
```json
{}
```
The request has no playload.
**Response**
```json
{
"Err": ""
}
```
If an error occurred during this request, add an error message to the `Err` field
in the response. If no error then you can either send an empty response (`{}`)
or an empty value for the `Err` field. Errors will only be logged.
|
