Get started with GCP Pub/Sub
Stream Postgres changes to a Google Cloud Pub/Sub topic
In this quickstart, you’ll create a real-time data pipeline that streams changes from a Postgres database to a Google Cloud Pub/Sub topic. You’ll:
- Boot Sequin
- Connect to a sample playground database
- Configure a Pub/Sub topic to receive database changes
- See your changes flow in real-time
By the end, you’ll have hands-on experience setting up Postgres change data capture (CDC) with Sequin. This same pattern can be used to setup your own Postgres CDC pipeline with Google Cloud Pub/Sub.
Prerequisites
- A Google Cloud project with Pub/Sub enabled
- A service account with Pub/Sub permissions
For this quickstart, you can use an existing service account with broad Pub/Sub permissions. For production use cases, we recommend creating a dedicated service account for Sequin with these specific roles:
roles/pubsub.publisher
roles/pubsub.viewer
For more information on creating a service account, see the how-to guide for Pub/Sub.
Create a Pub/Sub Topic
If you don’t already have a Pub/Sub topic:
- Navigate to the Pub/Sub Topics page in your Google Cloud Console
- Click “CREATE TOPIC”
- Enter a topic ID for this tutorial (e.g., “products”)
- Click “CREATE”
Make note of your:
- Google Cloud project ID (e.g., “my-project-123”)
- Pub/Sub topic ID (e.g., “products”)
Run Sequin
The easiest way to get started with Sequin is with our Docker Compose file. This file starts a Postgres database, Redis instance, and Sequin server.
Create directory and start services
- Download sequin-docker-compose.zip.
- Unzip the file.
- Navigate to the unzipped directory and start the services:
Verify services are running
Check that Sequin is running using docker ps
:
You should see output like the following:
All three containers should be up and running (status: Up
).
Login
The Docker Compose file automatically configures Sequin with an admin user and a playground database.
Let’s log in to the Sequin web console:
Open the web console
After starting the Docker Compose services, open the Sequin web console at http://localhost:7376:
Login with default credentials
Use the following default credentials to login:
- Email:
- Password:
View the playground database
To get you started quickly, Sequin’s Docker Compose file creates a logical database called sequin_playground
with a sample dataset in the public.products
table.
Let’s take a look:
Navigate to Databases
In the Sequin web console, click Databases in the sidebar.
Select playground database
Click on the pre-configured sequin-playground
database:
The database “Health” should be green.
View contents of the products table
Let’s get a sense of what’s in the products
table. Run the following command:
This command connects to the running Postgres container and runs a psql
command.
You should see a list of the rows in the products
table:
We’ll make modifications to this table in a bit.
Create a Pub/Sub Sink
With the playground database connected, you can create a sink. This sink will send changes to the products
table to your Pub/Sub topic:
Navigate to Sinks
Click “Sinks” in the sidebar navigation, then click “Create Sink”.
Select sink type
Select “Google Cloud Pub/Sub” as the sink type and click “Continue”.
Note "Source" configuration
In the “Source” card, note that the sequin-playground
database and products
table are pre-selected. Leave these defaults:
Setup a backfill
In the “Initial backfill” card, click the toggle to enable an initial backfill. You can leave the default start position, which will backfill all existing rows in the products
table:
Configure "Pub/Sub Configuration"
In the “Pub/Sub Configuration” card, enter your Pub/Sub details:
- Project ID: Your Google Cloud project ID
- Topic ID: The Pub/Sub topic to stream to (e.g., “products”)
- Service Account Credentials: Paste your service account JSON key file contents
Test the connection
At the bottom of the form, click the “Test Connection” button. If you provided proper credentials, it should succeed.
Sequin can connect to your Pub/Sub topic.
Create the sink
You can leave the rest of the defaults. As configured, the Pub/Sub topic will first receive a backfill of all rows currently in the products
table. Then, it will receive all changes to the products
table in real-time.
Click “Create Sink” to finish setting up your Pub/Sub sink.
See changes flow to your Pub/Sub topic
On the new sink’s overview page, you should see the “Health” status turn green, indicating data is flowing to your Pub/Sub topic.
Let’s confirm messages are flowing:
Messages tab
Click the “Messages” tab. You’ll see a list of the recently delivered messages:
Sequin indicates it backfilled the products
table to your Pub/Sub topic.
View in Pub/Sub Console
In the Google Cloud Console:
- Navigate to your Pub/Sub topic
- Click on the “MESSAGES” tab
- Under “Step 2”, select a Cloud Pub/Sub subscription
- Click “PULL” to see messages in the topic
You should see a list of messages appear in the table below. The messages are read
events from the initial backfill of the products
table.
Messages are flowing from Sequin to your Pub/Sub topic.
Make some changes
Let’s make some changes to the products
table and see them flow to your topic.
In your terminal, run the following command to insert a new row into the products
table:
In the Pub/Sub Console, click “PULL” again to see the new message appear.
Feel free to try other changes:
Each change will appear in your Pub/Sub topic within a few seconds.
Great work!
You’ve successfully:
- Set up a complete Postgres change data capture pipeline
- Loaded existing data through a backfill
- Made changes to the
products
table - Verified changes are flowing to your Pub/Sub topic
Ready to stream
Now you’re ready to connect your own database to Sequin and start streaming changes:
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