Automatic failover from primary region to secondary for internal service using Front Door or Traffic Manager

Question

I need to implement automatic failover to the secondary (passive) region for internal service. This service is a Function App that does some work on different events, including timers.

Here is my current understanding of how I can achieve this:

• Use SQL Server with the auto-failover group for leasing of leadership between regions. This approach is described here: https://www.youtube.com/watch?v=5h2aS0_YckI
• Use Cosmos DB with the single-write region and auto-failover. This is similar to the above approach. Some more info here: https://learn.microsoft.com/en-us/azure/cosmos-db/high-availability

My question now is if there is a solution how to implement it with Front Door or with Traffic Manager. Here is a sketch:

• Traffic Manager is set to Priority mode. The primary region has priority 1 and secondary 2. Both regions periodically send "Ping(name of region)" to the traffic manager URL. Now, the traffic manager directs these ping requests to the active, healthy region, so when a region receives a "Ping" message then it assumes that it is currently active, and performs work assuming to be a leader. It appears to make sense, but I'm concerned, if I can have a split-brain situation here (when both regions think they are active/leaders).

Can anyone please help reason if there is an approach with Traffic Manager or Front Door may work without split-brain?

Thank you very much in advance,

Answer 1

Hello @Andrew Syrov ,

Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.

You can combine SQL auto-failover groups with Azure Traffic manager priority routing method to setup automatic failover from primary region to secondary for business continuity with minimal downtime. You can refer the below article which shows the implementation of this scenario.
Reference : https://learn.microsoft.com/en-us/azure/azure-sql/database/designing-cloud-solutions-for-disaster-recovery#scenario-1-using-two-azure-regions-for-business-continuity-with-minimal-downtime

Azure traffic manager priority routing is selected when you want to have a primary service endpoint for all traffic. You can provide multiple backup endpoints in case the primary or one of the backup endpoints is unavailable. The Traffic Manager profile contains a prioritized list of service endpoints. By default, Traffic Manager sends all traffic to the primary (highest-priority) endpoint regardless of the availability of all endpoints. If the primary endpoint isn't available, Traffic Manager routes the traffic to the second endpoint.

Even when both the regions are active, the traffic manager will route all the traffic to the highest-priority endpoint and only route the traffic to secondary when primary fails/degrades.

Reference : https://learn.microsoft.com/en-us/azure/traffic-manager/traffic-manager-routing-methods
https://learn.microsoft.com/en-us/azure/traffic-manager/traffic-manager-monitoring

Kindly let us know if the above helps or you need further assistance on this issue.

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