Get started with GCP Pub/Sub

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 and GCP Pub/Sub.

This is the quickstart for streaming Postgres to GCP Pub/Sub. See the how-to guide for an explanation of how to use the GCP Pub/Sub sink or the reference for details on all configuration options.

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:

cd sequin-docker-compose && docker compose up -d

Alternative: Download with curl

curl -L https://github.com/sequinstream/sequin/releases/latest/download/sequin-docker-compose.zip -o sequin-docker-compose.zip \
  && unzip sequin-docker-compose.zip && rm sequin-docker-compose.zip
cd sequin-docker-compose && docker compose up -d

Alternative: Clone the repository

git clone git@github.com:sequinstream/sequin.git
cd sequin/docker
docker compose up -d

Verify services are running

Check that Sequin is running using docker ps:

docker ps

You should see output like the following:

CONTAINER ID   IMAGE                           COMMAND                  CREATED          STATUS                    PORTS                              NAMES
bd5c458cabde   sequin/sequin:latest            "/scripts/start_comm…"   11 seconds ago   Up 9 seconds              4000/tcp, 0.0.0.0:7376->7376/tcp   sequin-sequin-1
3bacd89765e7   grafana/grafana                 "/run.sh"                11 seconds ago   Up 11 seconds             0.0.0.0:3000->3000/tcp             sequin-sequin_grafana-1
3ad41319a66c   postgres:16                     "docker-entrypoint.s…"   11 seconds ago   Up 11 seconds (healthy)   0.0.0.0:7377->5432/tcp             sequin-sequin_postgres-1
6139a5fc4e80   redis:7                         "docker-entrypoint.s…"   11 seconds ago   Up 11 seconds             0.0.0.0:7378->6379/tcp             sequin-sequin_redis-1
7e07a5b052de   prom/prometheus                 "/bin/prometheus --c…"   11 seconds ago   Up 11 seconds             0.0.0.0:9090->9090/tcp             sequin-sequin_prometheus-1

Sequin, Postgres, Redis, Prometheus, and Grafana 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:

Sequin login page, allowing login with default credentials

Use the following default credentials to login:

Email:

admin@sequinstream.com

Password:

sequinpassword!

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:

docker exec -i sequin-sequin_postgres-1 \
  psql -U postgres -d sequin_playground -c \
  "select id, name, price from products;"

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:

  id |         name          | price 
----+-----------------------+-------
  1 | Avocados (3 pack)     |  5.99
  2 | Flank Steak (1 lb)    |  8.99
  3 | Salmon Fillet (12 oz) | 14.99
  4 | Baby Spinach (16 oz)  |  4.99
  5 | Sourdough Bread       |  6.99
  6 | Blueberries (6 oz)    |  3.99
(6 rows)

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 is selected and all schemas and tables are included. Leave these defaults:

Source card showing the sequin_playground database and products table

Setup a backfill

In the Inital backfill card, select the public.products table to initate a backfill when the sink is created.

Initial backfill card with public.products table selected

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:

docker exec -i sequin-sequin_postgres-1 \
  psql -U postgres -d sequin_playground -c \
  "insert into products (name, price) values ('Organic Honey (16 oz)', 12.99);"

In the Pub/Sub Console, click “PULL” again to see the new message appear.Feel free to try other changes:

Update a product's price

docker exec -i sequin-sequin_postgres-1 \
  psql -U postgres -d sequin_playground -c \
  "update products set price = 7.99 where name = 'Avocados (3 pack)';"

Change a product's name

docker exec -i sequin-sequin_postgres-1 \
  psql -U postgres -d sequin_playground -c \
  "update products set name = 'Organic Avocados (3 pack)' where name = 'Avocados (3 pack)';"

Delete a product

docker exec -i sequin-sequin_postgres-1 \
  psql -U postgres -d sequin_playground -c \
  "delete from products where name = 'Blueberries (6 oz)';"

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:

Guide: Connect Postgres

Connect your Postgres database to Sequin.

Guide: Setting up a Pub/Sub sink

Setup a Pub/Sub sink to send changes to your topic.

Get started

Sink setup guides

How-to guides

Concepts

Reference

Database setup guides

Tutorials

Get started with GCP Pub/Sub

Prerequisites

Create a Pub/Sub Topic

Run Sequin

Login

View the playground database

Create a Pub/Sub Sink

See changes flow to your Pub/Sub topic

Ready to stream

Guide: Connect Postgres

Guide: Setting up a Pub/Sub sink

​Prerequisites

Create a Pub/Sub Topic

Run Sequin

Login

View the playground database

Create a Pub/Sub Sink

See changes flow to your Pub/Sub topic

​Ready to stream

Guide: Connect Postgres

Guide: Setting up a Pub/Sub sink

Prerequisites

Ready to stream