AI Data Synchronization with PostgreSQL Logical Replication

Question

Pulumi · Accepted Answer

Logical replication in PostgreSQL enables a database cluster to publish data changes and for other database clusters to subscribe to those changes. This capability allows for data to be replicated from one PostgreSQL database to another in real-time and can be used to scale out a PostgreSQL database cluster or for analytical purposes, among others.

Using Pulumi's PostgreSQL provider, you can manage PostgreSQL resources such as database instances, logical replication slots, publications, and subscriptions which are necessary for setting up logical replication. Below is a step by step guide on how you would go about implementing logical replication between PostgreSQL databases using Pulumi with Python.

### Step 1: Define the Publication Database

A publication is a set of database changes that can be replicated. Firstly, you set up a publication on the source database where the data changes originate. You'll need to have a running PostgreSQL database that allows you to create publications.

### Step 2: Define the Subscription Database

The subscription is a downstream process that subscribes to a publication. The destination database must have a replication slot that the subscription will use.

### Step 3: Set up the Publication

In the source database, you will create a publication to define which data should be replicated. Publications can be set up to publish all tables or specific tables.

### Step 4: Set up the Subscription

On the destination database, you create a subscription to the previously defined publication. The subscription will specify the connection information and the replication slot it should use.

Now let's see how this looks in code. Below is a Pulumi program that sets up a PostgreSQL logical replication.

```python
import pulumi
import pulumi_postgresql as postgresql

# Create a PostgreSQL Server (the "publisher") that we will use for publication to replicate data from.
publisher_db = postgresql.Server("publisher-db",
    # Parameters like version, database instance type, etc., would be defined here.
    # These details depend on your specific setup and requirements.
)

# Create the PostgreSQL Database for the publication
publisher_database = postgresql.Database("publisher-database",
    server_name=publisher_db.name,
    # Other database-specific parameters would be set here as needed.
)

# Set up the publication.
# This typically requires superuser privileges on the database.
publication = postgresql.Publication("publication",
    name="my_publication",
    database=publisher_database.name,
    owner="my_superuser",  # The database user who will own the publication.
    all_tables=True,  # Set to `True` to publish all tables; adjust as needed.
    # Other parameters for fine-graining the publication can be added here.
)

# Create a PostgreSQL Server (the "subscriber") that will subscribe to the publication.
subscriber_db = postgresql.Server("subscriber-db",
    # As with the publisher, database instance specifications will be provided here.
)

# Create the PostgreSQL Database for the subscription
subscriber_database = postgresql.Database("subscriber-database",
    server_name=subscriber_db.name,
    # Other database-specific parameters set here as needed.
)

# Set up the subscription on the destination database.
# The subscription connects to the publisher and replicates the data.
subscription = postgresql.Subscription("subscription",
    name="my_subscription",
    database=subscriber_database.name,
    conninfo=f"host={publisher_db.address} port=5432 dbname={publisher_database.name}",  # Connection string to the publication database
    publications=[publication.name],  # Array of publication names to subscribe to.
    # More parameters can be adjusted here as per the requirements.
)

# Output the endpoint for the subscriber database
pulumi.export("subscriber_endpoint", subscriber_db.address)

```

In this program, `pulumi_postgresql.Server`, `pulumi_postgresql.Database`, `pulumi_postgresql.Publication`, and `pulumi_postgresql.Subscription` are resources provided by the PostgreSQL provider in Pulumi. They represent PostgreSQL servers, databases, publications, and subscriptions, respectively, which are essential components in setting up logical replication.

This code does not include specific details about configuring network access, authentication, and other vital operational considerations due to their dependence on your infrastructure. Ensure that you include these details based on your organizational practices and cloud provider configurations.