PolarDB:Create and manage a global database network

Prerequisites

Before you begin, make sure your primary cluster meets the following requirements:

• An Enterprise Edition cluster in the Cluster Edition series

• At least one read-only node

• One of the following engine versions:

  • MySQL 8.0.2

  • MySQL 8.0.1 with minor engine version 8.0.1.1.17 or later

  • MySQL 5.7 with minor engine version 5.7.1.0.21 or later

  • MySQL 5.6 with minor engine version 5.6.1.0.32 or later

Supported regions

GDN supports the following regions: all regions in the Chinese mainland, China (Hong Kong), Japan (Tokyo), South Korea (Seoul), Singapore, Malaysia (Kuala Lumpur), Indonesia (Jakarta), Philippines (Manila), Thailand (Bangkok), Germany (Frankfurt), US (Silicon Valley), US (Virginia), and UK (London).

Cross-border secondary cluster deployment requires a separate request. For details, see Add a secondary cluster.

Limits

Billing

You are charged for the clusters themselves and for inter-region data transfer. Transfer fees depend on whether data crosses the Chinese mainland border.

Cross-border fees are calculated based on the Redo Log data physically replicated from the primary cluster to the cross-border secondary cluster each hour. Estimate this volume by querying the log sequence number (LSN) position.

Example: At 09:00, the LSN maps to ib_logfile1/648143676. At 10:00, it maps to ib_logfile3/648142342. Each log file is 1 GB (1,073,741,824 bytes).

1. Written to ib_logfile1: 1,073,741,824 − 648,143,676 = 425,598,148 bytes

2. Written to ib_logfile2 (full file): 1,073,741,824 bytes

3. Written to ib_logfile3: 648,142,342 bytes

4. Total: 2,147,482,314 bytes = 2,147,482,314 / 1,073,741,824 = 1.999998 GB — Fee: 1.999998 GB × USD 0.80/GB = USD 1.5999984

Query the LSN position:

-- Query the current log write progress
SHOW STATUS LIKE 'Innodb_log_write_lsn';
+----------------------+------------+
| Variable_name        | Value      |
+----------------------+------------+
| Innodb_log_write_lsn | 1721889596 |
+----------------------+------------+

-- Convert LSN to physical file offset
SELECT lsn_to_pos(1721889596);
+------------------------+
| lsn_to_pos(1721889596) |
+------------------------+
| ib_logfile1/648143676  |
+------------------------+

Enabling the global domain name feature incurs additional fees for internal DNS resolution and inter-region data transfer. See Global domain name pricing.

Create a GDN

1. Log on to the PolarDB console. In the left navigation pane, click Global Database Network.

2. On the GDN page, click Create GDN.

3. In the Create GDN dialog box, configure the following parameters.

   Parameter	Description
   Compatibility	Select MySQL.
   Version	Fixed at Active-passive.
   Name	Enter a name for the GDN. The name does not need to be unique.
   Primary Region	Select the region where the primary cluster is located. Decide which cluster to designate as primary before selecting the region.
   Primary Cluster	Select the existing cluster to use as the primary cluster.
   Global Domain Name	Choose whether to enable the global domain name feature. A global domain name provides a unified endpoint for the GDN, enables nearest access, and remains unchanged after a primary cluster switchover.

4. Click OK.

The GDN appears on the GDN page. From there, add a secondary cluster to the GDN.

View GDN information

Log on to the PolarDB console, then click a GDN ID on the GDN page to open the details page.

View basic information

The details page shows the GDN's ID, Version, Compatible Database, GDN Name, and Created At.

View the cluster list

The cluster list shows all primary and secondary clusters across all regions in the GDN.

View replication latency

In the Network Topology section, click View Replication Latency. In the dialog box, filter by time period to view the replication latency.

Delete a GDN

A GDN can only be deleted when it contains only the primary cluster. Because a GDN cannot be restored after deletion and applications connected to it immediately lose database access, remove all secondary clusters before proceeding.

Console

1. Log on to the PolarDB console. In the left navigation pane, click Global Database Network.

2. On the GDN page, find the target GDN and click Delete in the Actions column.

   If Delete is grayed out, the GDN still has secondary clusters. Delete all secondary clusters first.

3. Review the information in the dialog box and click OK to confirm.

API

Use the DeleteGlobalDatabaseNetwork API operation to delete a GDN programmatically. Before calling this operation, remove all secondary clusters from the GDN.

FAQ

How many GDNs can I create per Alibaba Cloud account?

There is no limit on the number of GDNs per account.

Can I change the primary cluster of an existing GDN?

Yes. Switch over the primary cluster in the PolarDB console. We recommend that you always use the default non-forced switchover mode. The forced switchover mode has the following limitations: you cannot specify the new primary cluster, and the original primary cluster is detached from the GDN after the switchover. Therefore, the forced switchover mode is not suitable for scenarios where you need to replace the primary cluster in a GDN.

API reference

What's next

• Add and manage a secondary cluster

• Connect to a GDN

• Create a global domain name