Connectivity architecture in Azure Database for MySQL

This article explains the Azure Database for MySQL connectivity architecture as well as how the traffic is directed to your Azure Database for MySQL instance from clients both within and outside Azure.

Connectivity architecture

Connection to your Azure Database for MySQL is established through a gateway that is responsible for routing incoming connections to the physical location of your server in our clusters. The following diagram illustrates the traffic flow.

Overview of the connectivity architecture

As client connects to the database, the connection string to the server resolves to the gateway IP address. The gateway listens on the IP address on port 3306. Inside the database cluster, traffic is forwarded to appropriate Azure Database for MySQL. Therefore, in order to connect to your server, such as from corporate networks, it is necessary to open up the client-side firewall to allow outbound traffic to be able to reach our gateways. Below you can find a complete list of the IP addresses used by our gateways per region.

Azure Database for MySQL gateway IP addresses

The gateway service is hosted on group of stateless compute nodes sitting behind an IP address, which your client would reach first when trying to connect to an Azure Database for MySQL server.

As part of ongoing service maintenance, we will periodically refresh compute hardware hosting the gateways to ensure we provide the most secure and performant experience. When the gateway hardware is refreshed, a new ring of the compute nodes is built out first. This new ring serves the traffic for all the newly created Azure Database for MySQL servers and it will have a different IP address from older gateway rings in the same region to differentiate the traffic. Once the new ring is fully functional, the older gateway hardware serving existing servers are planned for decommissioning. Before decommissioning a gateway hardware, customers running their servers and connecting to older gateway rings will be notified via email and in the Azure portal, three months in advance before decommissioning. The decommissioning of gateways can impact the connectivity to your servers if

  • You hard code the gateway IP addresses in the connection string of your application. It is not recommended. You should use fully qualified domain name (FQDN) of your server in the format .mysql.database.azure.com, in the connection string for your application.
  • You do not update the newer gateway IP addresses in the client-side firewall to allow outbound traffic to be able to reach our new gateway rings.

The following table lists the gateway IP addresses of the Azure Database for MySQL gateway for all data regions. The most up-to-date information of the gateway IP addresses for each region is maintained in the table below. In the table below, the columns represent following:

  • Gateway IP addresses: This column lists the current IP addresses of the gateways hosted on the latest generation of hardware. If you are provisioning a new server, we recommend that you open the client-side firewall to allow outbound traffic for the IP addresses listed in this column.
  • Gateway IP addresses (decommissioning): This column lists the IP addresses of the gateways hosted on an older generation of hardware that is being decommissioned right now. If you are provisioning a new server, you can ignore these IP addresses. If you have an existing server, continue to retain the outbound rule for the firewall for these IP addresses as we have not decommissioned it yet. If you drop the firewall rules for these IP addresses, you may get connectivity errors. Instead, you are expected to proactively add the new IP addresses listed in Gateway IP addresses column to the outbound firewall rule as soon as you receive the notification for decommissioning. This will ensure when your server is migrated to latest gateway hardware, there is no interruptions in connectivity to your server.
  • Gateway IP addresses (decommissioned): This columns lists the IP addresses of the gateway rings, which are decommissioned and are no longer in operations. You can safely remove these IP addresses from your outbound firewall rule.
Region name Gateway IP addresses Gateway IP addresses (decommissioning) Gateway IP addresses (decommissioned)
Australia Central 20.36.105.0
Australia Central2 20.36.113.0
Australia East 13.75.149.87, 40.79.161.1
Australia South East 191.239.192.109, 13.73.109.251
Brazil South 191.233.201.8, 191.233.200.16 104.41.11.5
Canada Central 40.85.224.249
Canada East 40.86.226.166
Central US 23.99.160.139, 52.182.136.37, 52.182.136.38 13.67.215.62
China East 139.219.130.35
China East 2 40.73.82.1
China North 139.219.15.17
China North 2 40.73.50.0
East Asia 191.234.2.139, 52.175.33.150, 13.75.33.20, 13.75.33.21
East US 40.71.8.203, 40.71.83.113 40.121.158.30 191.238.6.43
East US 2 40.70.144.38, 52.167.105.38 52.177.185.181
France Central 40.79.137.0, 40.79.129.1
France South 40.79.177.0
Germany Central 51.4.144.100
Germany North 51.116.56.0
Germany North East 51.5.144.179
Germany West Central 51.116.152.0
India Central 104.211.96.159
India South 104.211.224.146
India West 104.211.160.80
Japan East 40.79.192.23, 40.79.184.8 13.78.61.196
Japan West 191.238.68.11, 40.74.96.6, 40.74.96.7 104.214.148.156
Korea Central 52.231.17.13 52.231.32.42
Korea South 52.231.145.3 52.231.200.86
North Central US 52.162.104.35, 52.162.104.36 23.96.178.199
North Europe 52.138.224.6, 52.138.224.7 40.113.93.91 191.235.193.75
South Africa North 102.133.152.0
South Africa West 102.133.24.0
South Central US 104.214.16.39, 20.45.120.0 13.66.62.124 23.98.162.75
South East Asia 40.78.233.2, 23.98.80.12 104.43.15.0
Switzerland North 51.107.56.0
Switzerland West 51.107.152.0
UAE Central 20.37.72.64
UAE North 65.52.248.0
UK South 51.140.184.11
UK West 51.141.8.11
West Central US 13.78.145.25
West Europe 13.69.105.208, 104.40.169.187 40.68.37.158 191.237.232.75
West US 13.86.216.212, 13.86.217.212 104.42.238.205 23.99.34.75
West US 2 13.66.136.192 13.66.226.202

Connection redirection

Azure Database for MySQL supports an additional connection policy, redirection, that helps to reduce network latency between client applications and MySQL servers. With redirection, and after the initial TCP session is established to the Azure Database for MySQL server, the server returns the backend address of the node hosting the MySQL server to the client. Thereafter, all subsequent packets flow directly to the server, bypassing the gateway. As packets flow directly to the server, latency and throughput have improved performance.

This feature is supported in Azure Database for MySQL servers with engine versions 5.6, 5.7, and 8.0.

Support for redirection is available in the PHP mysqlnd_azure extension, developed by Microsoft, and is available on PECL. See the configuring redirection article for more information on how to use redirection in your applications.

Important

Support for redirection in the PHP mysqlnd_azure extension is currently in preview.

Frequently asked questions

What you need to know about this planned maintenance?

This is a DNS change only which makes it transparent to clients. While the IP address for FQDN is changed in the DNS server, the local DNS cache will be refreshed within 5 minutes, and it is automatically done by the operating systems. After the local DNS refresh, all the new connections will connect to the new IP address, all existing connections will remain connected to the old IP address with no interruption until the old IP addresses are fully decommissioned. The old IP address will roughly take three to four weeks before getting decommissioned; therefore, it should have no effect on the client applications.

What are we decommissioning?

Only Gateway nodes will be decommissioned. When users connect to their servers, the first stop of the connection is to gateway node, before connection is forwarded to server. We are decommissioning old gateway rings (not tenant rings where the server is running) refer to the connectivity architecture for more clarification.

How can you validate if your connections are going to old gateway nodes or new gateway nodes?

Ping your server’s FQDN, for example ping xxx.mysql.database.azure.com. If the returned IP address is one of the IPs listed under Gateway IP addresses (decommissioning) in the document above, it means your connection is going through the old gateway. Contrarily, if the returned Ip address is one of the IPs listed under Gateway IP addresses, it means your connection is going through the new gateway.

You may also test by PSPing or TCPPing the database server from your client application with port 3306 and ensure that return IP address isn't one of the decommissioning IP addresses

How do I know when the maintenance is over and will I get another notification when old IP addresses are decommissioned?

You will receive an email to inform you when we will start the maintenance work. The maintenance can take up to one month depending on the number of servers we need to migrate in al regions. Please prepare your client to connect to the database server using the FQDN or using the new IP address from the table above.

What do I do if my client applications are still connecting to old gateway server ?

This indicates that your applications connect to server using static IP address instead of FQDN. Review connection strings and connection pooling setting, AKS setting, or even in the source code.

Is there any impact for my application connections?

This maintenance is just a DNS change, so it is transparent to the client. Once the DNS cache is refreshed in the client (automatically done by operation system), all the new connection will connect to the new IP address and all the existing connection will still working fine until the old IP address fully get decommissioned, which usually several weeks later. And the retry logic is not required for this case, but it is good to see the application have retry logic configured. Please either use FQDN to connect to the database server or enable list the new 'Gateway IP addresses' in your application connection string. This maintenance operation will not drop the existing connections. It only makes the new connection requests go to new gateway ring.

Can I request for a specific time window for the maintenance?

As the migration should be transparent and no impact to customer's connectivity, we expect there will be no issue for majority of users. Review your application proactively and ensure that you either use FQDN to connect to the database server or enable list the new 'Gateway IP addresses' in your application connection string.

No, this is a gateway hardware decommission and have no relation to private link or private IP addresses, it will only affect public IP addresses mentioned under the decommissioning IP addresses.

Next steps