What is Azure Traffic Manager?

Azure Traffic Manager is a DNS-based traffic load balancer that allows you to distribute traffic optimally to your services hosted in Azure or even externally. It enables you to achieve high availability and responsiveness for your applications by directing users to the most appropriate endpoint based on their geographic location, network latency, or other defined traffic-management methods.

Traffic Manager works at the DNS layer. When a user's DNS resolver queries for your application's domain name, Traffic Manager responds with the IP address of the chosen endpoint. This ensures that users are directed to the closest or best-performing instance of your application.

How Traffic Manager Works

The core mechanism involves creating a Traffic Manager profile associated with a unique DNS name (e.g., myapp.trafficmanager.net). You then add endpoints to this profile, which can be Azure services (like Web Apps, Cloud Services, VMs) or even external endpoints.

When a DNS query is received for your Traffic Manager domain name, Traffic Manager evaluates the configured traffic-management method and the health of the endpoints. It then returns the DNS record (A, AAAA, or CNAME) for the selected endpoint.

Traffic Manager does not proxy traffic. It only provides DNS resolution. The actual application traffic flows directly from the client to the selected endpoint.

Traffic-Rerouting Methods

Traffic Manager offers several intelligent routing methods to suit different scenarios:

  • Priority: Directs all traffic to a primary endpoint. If it becomes unavailable, Traffic Manager automatically routes traffic to a secondary (failover) endpoint, and so on. This is ideal for creating active-passive failover configurations.
  • Weighted: Distributes traffic across a set of endpoints based on assigned weights. For example, you can send 70% of traffic to one endpoint and 30% to another, allowing for phased rollouts or A/B testing.
  • Performance: Directs users to the endpoint with the lowest network latency. This is achieved by measuring the latency from various geographic locations to your endpoints and choosing the fastest one.
  • Geographic: Directs users to specific endpoints based on their geographic location (e.g., users in Europe are routed to European endpoints).
  • Multi-value: Returns up to three healthy IP addresses for the requested resource, allowing the client to attempt connection to multiple endpoints.
  • Subnet: Directs users to specific endpoints based on their IP address subnet.

Creating a Traffic Manager Profile

You can create a Traffic Manager profile through the Azure portal, Azure CLI, or PowerShell. Here's a simplified overview using the Azure portal:

  1. Navigate to the Azure portal.
  2. Search for "Traffic Manager profiles" and select it.
  3. Click "+ Create".
  4. Provide a name for your profile, select the resource group, and choose the desired routing method.
  5. Configure the DNS TTL (Time To Live).
  6. Click "Review + create" and then "Create".

Configuring Endpoints

Once a profile is created, you need to add endpoints:

  1. Open your Traffic Manager profile.
  2. Under "Settings", click "Endpoints".
  3. Click "+ Add".
  4. Select the endpoint type (e.g., "Azure endpoint", "External endpoint", "Nested endpoint").
  5. Provide the required details, such as the target resource, priority, weight, or geographic region depending on your routing method.
  6. Click "OK" or "Add".

Endpoint Health Monitoring

Traffic Manager continuously monitors the health of your endpoints to ensure traffic is only directed to available services. You can configure the monitoring settings, including:

  • Protocol: HTTP, HTTPS, or TCP.
  • Port: The port to monitor.
  • Path (for HTTP/HTTPS): A specific URL path to probe.
  • Interval: How often to check endpoint health.
  • Tolerated number of failures: How many consecutive failures before an endpoint is considered unhealthy.
For HTTP/HTTPS probes, consider using a specific path that reflects the application's health status rather than just the root page.

Monitoring Traffic Manager

Azure provides comprehensive monitoring capabilities for Traffic Manager profiles. You can view traffic patterns, endpoint health status, and historical performance data directly within the Azure portal.

Integration with Azure Monitor allows you to set up alerts based on specific metrics or events, such as an endpoint becoming unhealthy or a significant change in traffic.

Key Metrics to Monitor:

  • Endpoint health status
  • DNS query counts
  • Latency to endpoints
  • Traffic distribution (for Weighted and Performance methods)

Best Practices for Traffic Manager

  • Use multiple regions: Deploy your application across different Azure regions for disaster recovery and improved performance.
  • Configure health probes carefully: Ensure your probes accurately reflect the availability of your application.
  • Set appropriate TTL values: A lower TTL can improve failover times but may increase DNS query load.
  • Test failover scenarios: Regularly test your failover configurations to ensure they work as expected.
  • Document your configuration: Keep clear records of your Traffic Manager setup, including endpoints, routing methods, and monitoring settings.