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Create and manage read replicas in Azure Database for PostgreSQL - Flexible Server from the Azure portal

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APPLIES TO: Azure Database for PostgreSQL - Flexible Server

In this article, you learn how to create and manage read replicas in Azure Database for PostgreSQL from the Azure portal. To learn more about read replicas, see the overview.

Prerequisites

An Azure Database for PostgreSQL server to be the primary server.

Note

When deploying read replicas for persistent heavy write-intensive primary workloads, the replication lag could continue to grow and may never be able to catch-up with the primary. This may also increase storage usage at the primary as the WAL files are not deleted until they are received at the replica.

Create a read replica

To create a read replica, follow these steps:

  1. Select an existing Azure Database for PostgreSQL server to use as the primary server.

  2. On the server sidebar, under Settings, select Replication.

  3. Select Add Replica.

    Add a replica

  4. Enter the Basics form with the following information.

    Enter the Basics information

    Note

    To learn more about which regions you can create a replica in, visit the read replica concepts article.

  5. Select Review + create to confirm the creation of the replica or Next: Networking if you want to add, delete or modify any firewall rules. Modify firewall rules

  6. Leave the remaining defaults and then select the Review + create button at the bottom of the page or proceed to the next forms to add tags or change data encryption method.

  7. Review the information in the final confirmation window. When you're ready, select Create. Review the information in the final confirmation window

After the read replica is created, it can be viewed from the Replication window.

View the new replica in the Replication window

Important

Review the considerations section of the Read Replica overview.

To avoid issues during promotion of replicas always change the following server parameters on the replicas first, before applying them on the primary: max_connections, max_prepared_transactions, max_locks_per_transaction, max_wal_senders, max_worker_processes.

Promote replicas

You can promote replicas to become stand-alone servers serving read-write requests.

Important

Promotion of replicas cannot be undone. The read replica becomes a standalone server that supports both reads and writes. The standalone server can't be made into a replica again.

To promote replica from the Azure portal, follow these steps:

  1. In the Azure portal, select your primary Azure Database for PostgreSQL server.

  2. On the server menu, under Settings, select Replication.

  3. Select the replica server for which to stop replication and hit Promote.

    Select the replica

  4. Confirm promote operation.

    Confirm to promote replica

Delete a primary server

You can only delete primary server once all read replicas have been deleted. Follow the instruction in Delete a replica section to delete replicas and then proceed with steps below.

To delete a server from the Azure portal, follow these steps:

  1. In the Azure portal, select your primary Azure Database for PostgreSQL server.

  2. Open the Overview page for the server and select Delete.

    On the server Overview page, select to delete the primary server

  3. Enter the name of the primary server to delete. Select Delete to confirm deletion of the primary server.

    Confirm to delete the primary server

Delete a replica

You can delete a read replica similar to how you delete a standalone Azure Database for PostgreSQL server.

  • In the Azure portal, open the Overview page for the read replica. Select Delete.

    On the replica Overview page, select to delete the replica

You can also delete the read replica from the Replication window by following these steps:

  1. In the Azure portal, select your primary Azure Database for PostgreSQL server.

  2. On the server menu, under Settings, select Replication.

  3. Select the read replica to delete and hit the Delete button.

    Select the replica to delete

  4. Acknowledge Delete operation.

    Confirm to delete te replica

Monitor a replica

Two metrics are available to monitor read replicas.

Max Physical Replication Lag

Available only on the primary.

The Max Physical Replication Lag metric shows the lag in bytes between the primary server and the most-lagging replica.

  1. In the Azure portal, select the primary server.

  2. Select Metrics. In the Metrics window, select Max Physical Replication Lag.

    Screenshot of the Metrics blade showing Max Physical Replication Lag metric.

  3. For your Aggregation, select Max.

Read Replica Lag metric

Available only on replicas.

The Read Replica Lag metric shows the time since the last replayed transaction on a replica. If there are no transactions occurring on your primary, the metric reflects this time lag. For instance if there are no transactions occurring on your primary server, and the last transaction was replayed 5 seconds ago, then the Read Replica Lag will show 5 second delay.

  1. In the Azure portal, select read replica.

  2. Select Metrics. In the Metrics window, select Read Replica Lag.

    screenshot of the Metrics blade showing Read Replica Lag metric.

  3. For your Aggregation, select Max.

Next steps