> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mage.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Google Cloud PubSub

## Basic config

```yaml theme={"system"}
connector_type: google_cloud_pubsub
project_id: test-project-id
topic_id: test-topic-id
pubsub_emulator_host: null  # "host.docker.internal:8085"
path_to_credentials_json_file: "./google_credentials.json"
```

The `pubsub_emulator_host` parameter is optional, which could be used when you need to test
the Google Cloud PubSub service locally through an emulator (see more details at the bottom).

## Data format

The Google Cloud PubSub data exporter scalar values

```
message = <Any>
```

or dictionaries with a specific format as messages:

```
message = {
    'data': <Any>,
    'metadata': <Optional[Dict]>
}
```

If the data contains no dictionary it will be written to the pubsub as value.
Otherwise, every dictionary message contains at least some data in a `data` field.
The following messages are valid:

```python theme={"system"}
message = {'data': {'bees': 23, 'ants': 30}}
```

The following message shows the configuration of elements data:

```python theme={"system"}
message = {
    'data': {
        'bees': 23,
        'ants': 30,
    }
}
```

If not all elements are configured, default values are assumed.

* The project\_id and topic\_id has to be configured in the yaml file.

```yaml theme={"system"}
connector_type: google_cloud_pubsub
project_id: test-project-id
topic_id: test-topic-id
```

## Set up Google Cloud Pubsub emulator

To test out Google Cloud PubSub source locally, follow the instructions in
[Testing apps locally with the emulator](https://cloud.google.com/pubsub/docs/emulator)
to set up the local Google Cloud PubSub emulator.

## Create a `project_id` for testing

Use the command listed under the `Starting the emulator` section to create a `project_id`, e.g.,

```
gcloud beta emulators pubsub start --project=test-project-id

$(gcloud beta emulators pubsub env-init)
```

## Create a topic and a subscription

Use the `gcloud pubsub topics create` command to create a topic:

```
gcloud pubsub topics create test-topic-id
```

After you create a topic, you can subscribe or publish to it. Use the
`gcloud pubsub subscriptions create` command to create a subscription.

```
gcloud pubsub subscriptions create test-subscription-id-0 --topic test-topic-id
```

Only messages published to the topic after the subscription is created
are available to subscriber applications.