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Virtual endpoints for read replicas in Azure Database for PostgreSQL - Flexible Server

  • Artikkeli

APPLIES TO: Azure Database for PostgreSQL - Flexible Server

Virtual Endpoints are read-write and read-only listener endpoints, that remain consistent irrespective of the current role of the Azure Database for PostgreSQL flexible server instance. This means you don't have to update your application's connection string after performing the promote to primary server action, as the endpoints will automatically point to the correct instance following a role change.

All operations involving virtual endpoints, whether adding, editing, or removing, are performed in the context of the primary server. In the Azure portal, you manage these endpoints under the primary server page. Similarly, when using tools like the CLI, REST API, or other utilities, commands and actions target the primary server for endpoint management.

Virtual Endpoints offer two distinct types of connection points:

Writer Endpoint (Read/Write): This endpoint always points to the current primary server. It ensures that write operations are directed to the correct server, irrespective of any promote operations users trigger. This endpoint can't be changed to point to a replica.

Read-Only Endpoint: This endpoint can be configured by users to point either to a read replica or the primary server. However, it can only target one server at a time. Load balancing between multiple servers isn't supported. You can adjust the target server for this endpoint anytime, whether before or after promotion.

Note

You can create only one writer and one read-only endpoint per primary and one of its replica.

Virtual Endpoints and Promote Behavior

In the event of a promote action, the behavior of these endpoints remains predictable. The sections below delve into how these endpoints react to both Promote to primary server and Promote to independent server scenarios.

Virtual endpoint Original target Behavior when "Promote to primary server" is triggered Behavior when "Promote to independent server" is triggered
Writer endpoint Primary Points to the new primary server. Remains unchanged.
Read-Only endpoint Replica Points to the new replica (former primary). Points to the primary server.
Read-Only endpoint Primary Not supported. Remains unchanged.

Behavior when "Promote to primary server" is triggered

  • Writer Endpoint: This endpoint is updated to point to the new primary server, reflecting the role switch.
  • Read-Only endpoint
    • If Read-Only Endpoint Points to Replica: After the promote action, the read-only endpoint will point to the new replica (the former primary).
    • If Read-Only Endpoint Points to Primary: For the promotion to function correctly, the read-only endpoint must be directed at the server intended to be promoted. Pointing to the primary, in this case, isn't supported and must be reconfigured to point to the replica prior to promotion.

Behavior when "Promote to the independent server and remove from replication" is triggered

  • Writer Endpoint: This endpoint remains unchanged. It continues to direct traffic to the server, holding the primary role.
  • Read-Only endpoint
    • If Read-Only Endpoint Points to Replica: The Read-Only endpoint is redirected from the promoted replica to point to the primary server.
    • If Read-Only Endpoint Points to Primary: The Read-Only endpoint remains unchanged, continuing to point to the same server.

Using Virtual Endpoints for Consistent Hostname During Point-in-Time Recovery (PITR) or Snapshot Restore

This section explains how to use Virtual Endpoints in Azure Database for PostgreSQL - Flexible Server to maintain a consistent hostname during Point-in-Time Recovery (PITR) or Snapshot Restore, ensuring application connection strings remain unchanged. Follow below steps:

  1. Add Virtual Endpoint to Primary Server:

    • Browse to your primary server instance in the Azure Portal.
    • Navigate to Replication Tab, and under Virtual Endpoints, click Add Virtual Endpoint.
    • Configure the virtual endpoint with a consistent hostname (e.g., mydb-virtual-endpoint.postgres.database.azure.com).
    • Save the configuration.
    • Update your application to use this virtual endpoint in the connection string.

  2. Perform Point-in-Time-Restore (PITR) or Snapshot Restore:

    • Initiate Recovery:
      • Go to the Backups section of your primary server.
      • Choose the appropriate restore option (PITR or snapshot) and specify the desired point in time.
    • Update Virtual Endpoint:
      • Once the new instance is created, navigate back to the old primary server Replication Tab.
      • Remove the virtual endpoint from the original primary server. Old Primary should be in succeeded state to remove the virtual endpoint
      • Add the same virtual endpoint to the newly created server.

  3. Validation:

    • Ensure that your application connects using the virtual endpoint and verify the database operations post-recovery.

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