Azure DB for PostgreSQL Migration Move Public IP Address

Vision Intelligence 60

Need to migrate an existing Azure Database for PostgreSQL - Single Server over to Azure Database for PostgreSQL - Flexible Server. The single server has a standard azure "Public (FQDN) address" of xxxxx.postgres.database.azure.com. How can I move / point this FQDN to the new Flexible server after migration has completed so that all of the database clients now connect to the Flexible server without configuration change?

Oury Ba-MSFT 20,176 Reputation points Microsoft Employee

2025-01-21T23:26:25.7833333+00:00

@Vision Intelligence Thank you for reaching out.

The below doc should help. If you are stuck with migration process, please let us know whereby sharing screen shot. As I have mentioned in your previous post "If both are publicly accessed as you mentioned, no vnet ..etc so no further action needed at networking level.

As mentioned by @Rahul Randive , the Custom FQDN/IP field is optional and can be used when the target is behind a custom DNS server or has custom DNS namespaces

https://learn.microsoft.com/en-us/azure/postgresql/migrate/migration-service/tutorial-migration-service-single-to-flexible?tabs=portal%2Coffline
Vision Intelligence 60 Reputation points

2025-01-22T11:26:55.3833333+00:00

Please see my reply to @Rahul Randive. When migration is completed, I just want to know what the options are for somehow redirecting requests to the original azure DB single server @ "server-name1.postgres.database.azure.com" to the newly created azure DB flexible server @ "server-name2.postgres.database.azure.com" . Does the migration service automatically perform a "switch-over"? Is this a manual process (I would prefer the manual approach to control when it gets used). Do I have to do some kind of DNS zone configuration? I presently do not have any DNS stuff set up to do this. Please advise. Migration workflow / instructions should contain discussion about redirecting / switchover. Thank you.

1 answer

RahulRandive 10,146 Reputation points

2025-01-21T23:26:45.4233333+00:00

Hi @Vision Intelligence

I believe After the migration is complete, you can update the DNS records to point the existing FQDN (e.g., xxxxx.postgres.database.azure.com) to the new Flexible Server's IP address.
Or If your Flexible Server is behind a custom DNS server or uses custom DNS namespaces, you can set up a DNS entry to resolve the new Flexible Server to the same FQDN that was previously used by the Single Server

Here is related information from the migration document https://learn.microsoft.com/en-us/azure/postgresql/migrate/migration-service/tutorial-migration-service-single-to-flexible?tabs=portal%2Coffline#select-migration-target

Select migration target

The Select migration target section displays metadata for the Flexible Server target, such as Subscription, Resource group, Server name, Location, and PostgreSQL version.

The Custom FQDN/IP field is optional and can be used when the target is behind a custom DNS server or has custom DNS namespaces, making it accessible only via specific FQDNs or IP addresses. For example, this could include entries like flexibleserver.example.com, 198.1.0.2, or a PostgreSQL FQDN such as flexibleserver.postgres.database.azure.com, if the custom DNS server contains the DNS zone postgres.database.azure.com or forwards queries for this zone to 168.63.129.16, where the FQDN is resolved in the Azure public or private DNS zone.

Thank You
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Vision Intelligence 60 Reputation points

2025-01-22T11:17:15.23+00:00

Thank you for your response.

I didn't realize it was possible to control what "xxxxx.postgres.database.azure.com" actually points to. After the migration is completed, how do I "redirect" this "xxxxx.postgres.database.azure.com" to actually resolve to "yyyyy.postgres.database.azure.com" ? Do I need to create a new Azure DNS zone specifically for "postgres.database.azure.com"? Not sure how this is typically handled. If this is true, then I guess this is how I would manually switch over / "redirect" requests to "xxxxx.postgres.database.azure.com" over to the newly created "yyyyy.postgres.database.azure.com"?

When setting up the migration "Source" I didn't realize I didn't actually need to provide the full FQDN, and all I needed to provide was the "Server name" field . I guess the migration service is smart enough to know that if I don't provide the FQDN info, it defaults to looking for the "Server name" in "postgres.database.azure.com". When setting up the migration target it looks like I don't need to provide the "Server name" and the FQDN since we are already in the context of the target when performing the migration.

RahulRandive 10,146 Reputation points

2025-01-22T20:14:24.5633333+00:00

Hi @Vision Intelligence ,

To redirect "xxxxx.postgres.database.azure.com" to "yyyyy.postgres.database.azure.com" after migration, you need to manage DNS settings.

Create a Private DNS Zone: You may need to create a private DNS zone in your subscription ending with postgres.database.azure.com.

Link the Private DNS Zone: Link the private DNS zone to the Virtual Network (VNET)

DNS Forwarding: Set up DNS forwarding rules to forward requests to postgres.database.azure.com. If you use a custom DNS server, you must use a DNS forwarder to resolve the FQDN of Azure Database for PostgreSQL - Flexible Server. The forwarder IP address should be 168.63.129.16.

Vision Intelligence 60 Reputation points

2025-01-22T21:13:37.5466667+00:00

Thank you for your response.

Does this approach assume the external clients can reach this virtual network? I would need an approach that allows external internet clients to connect to "xxxxx.postgres.database.azure.com", and SOMETHING forwards this to ""yyyyy.postgres.database.azure.com"

RahulRandive 10,146 Reputation points

2025-01-22T23:06:11.7633333+00:00

Hi @Vision Intelligence
Above approach assumes that the clients are within the virtual network or can reach the virtual network.

For external internet clients, I believe you need to use a public DNS to manage the redirection. I think you can create a CNAME record in your public DNS zone.

Vision Intelligence 60 Reputation points

2025-01-23T10:19:34.7966667+00:00

I think what you are saying is...This would then probably require clients to first move their database connection string to a string that is resolved by a public DNS zone, right? Clients that have a connection string using "xxxxx.postgres.database.azure.com" would need to change to using "thedatabase.mycompany.com". Then my "mycompany" DNS zone could have a CNAME entry to forward "thedatabase" to "yyyyy.postgres.database.azure.com". Do I understand this correctly?
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Azure DB for PostgreSQL Migration Move Public IP Address

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