---
title: "discovery.gce | Grafana Agent documentation"
description: "Learn about discovery.gce"
---

> For a curated documentation index, see [llms.txt](/llms.txt). For the complete documentation index, see [llms-full.txt](/llms-full.txt).

# discovery.gce

`discovery.gce` allows retrieving scrape targets from [Google Compute Engine](https://cloud.google.com/compute) (GCE) instances. The private IP address is used by default, but may be changed to the public IP address with relabeling.

Credentials are discovered by the Google Cloud SDK default client by looking in the following places, preferring the first location found:

1. a JSON file specified by the `GOOGLE_APPLICATION_CREDENTIALS` environment variable.
2. a JSON file in the well-known path `$HOME/.config/gcloud/application_default_credentials.json`.
3. fetched from the GCE metadata server.

If the Agent is running within GCE, the service account associated with the instance it is running on should have at least read-only permissions to the compute resources. If running outside of GCE make sure to create an appropriate service account and place the credential file in one of the expected locations.

## Usage

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
discovery.gce "LABEL" {
  project = PROJECT_NAME
  zone    = ZONE_NAME
}
```

## Arguments

The following arguments are supported:

Expand table

| Name               | Type       | Description                                                                                                             | Default | Required |
|--------------------|------------|-------------------------------------------------------------------------------------------------------------------------|---------|----------|
| `project`          | `string`   | The GCP Project.                                                                                                        |         | yes      |
| `zone`             | `string`   | The zone of the scrape targets.                                                                                         |         | yes      |
| `filter`           | `string`   | Filter can be used optionally to filter the instance list by other criteria.                                            |         | no       |
| `refresh_interval` | `duration` | Refresh interval to re-read the instance list.                                                                          | `"60s"` | no       |
| `port`             | `int`      | The port to scrape metrics from. If using the public IP address, this must instead be specified in the relabeling rule. | `80`    | no       |
| `tag_separator`    | `string`   | The tag separator is used to separate the tags on concatenation.                                                        | `","`   | no       |

For more information on the syntax of the `filter` argument, refer to Google’s `filter` documentation for [Method: instances.list](https://cloud.google.com/compute/docs/reference/latest/instances/list).

## Exported fields

The following fields are exported and can be referenced by other components:

Expand table

| Name      | Type                | Description                        |
|-----------|---------------------|------------------------------------|
| `targets` | `list(map(string))` | The set of discovered GCE targets. |

Each target includes the following labels:

- `__meta_gce_instance_id`: the numeric id of the instance
- `__meta_gce_instance_name`: the name of the instance
- `__meta_gce_label_LABEL_NAME`: each GCE label of the instance
- `__meta_gce_machine_type`: full or partial URL of the machine type of the instance
- `__meta_gce_metadata_NAME`: each metadata item of the instance
- `__meta_gce_network`: the network URL of the instance
- `__meta_gce_private_ip`: the private IP address of the instance
- `__meta_gce_interface_ipv4_NAME`: IPv4 address of each named interface
- `__meta_gce_project`: the GCP project in which the instance is running
- `__meta_gce_public_ip`: the public IP address of the instance, if present
- `__meta_gce_subnetwork`: the subnetwork URL of the instance
- `__meta_gce_tags`: comma separated list of instance tags
- `__meta_gce_zone`: the GCE zone URL in which the instance is running

## Component health

`discovery.gce` is only reported as unhealthy when given an invalid configuration. In those cases, exported fields retain their last healthy values.

## Debug information

`discovery.gce` does not expose any component-specific debug information.

## Debug metrics

`discovery.gce` does not expose any component-specific debug metrics.

## Example

Alloy ![Copy code to clipboard](/media/images/icons/icon-copy-small-2.svg) Copy

```alloy
discovery.gce "gce" {
  project = "agent"
  zone    = "us-east1-a"
}

prometheus.scrape "demo" {
  targets    = discovery.gce.gce.targets
  forward_to = [prometheus.remote_write.demo.receiver]
}

prometheus.remote_write "demo" {
  endpoint {
    url = PROMETHEUS_REMOTE_WRITE_URL

    basic_auth {
      username = USERNAME
      password = PASSWORD
    }
  }
}
```

Replace the following:

- `PROMETHEUS_REMOTE_WRITE_URL`: The URL of the Prometheus remote\_write-compatible server to send metrics to.
- `USERNAME`: The username to use for authentication to the remote\_write API.
- `PASSWORD`: The password to use for authentication to the remote\_write API.

## Compatible components

`discovery.gce` has exports that can be consumed by the following components:

- Components that consume [Targets](../../compatibility/#targets-consumers)

> Note
> 
> Connecting some components may not be sensible or components may require further configuration to make the connection work correctly. Refer to the linked documentation for more details.