Azure Traffic Manager Explained

What is Azure Traffic Manager?

Azure Traffic Manager is a DNS-based traffic load balancer that enables you to distribute traffic optimally to your services hosted in Azure or even externally. It allows you to control the distribution of end-user traffic to your application endpoints, by performing DNS lookups on behalf of the client. Traffic Manager is highly available and reliable, ensuring that your applications remain accessible even in the event of an outage.

Key Concepts

Traffic Manager works by using DNS to direct clients to the most appropriate endpoint based on a chosen traffic-routing method.

Traffic-Routing Methods

Traffic Manager supports several traffic-routing methods:

• Priority: Directs all traffic to a primary endpoint, with backup endpoints for failover.
• Weighted: Distributes traffic across a set of endpoints based on configured weights.
• Performance: Routes users to the closest (lowest latency) endpoint.
• Geographic: Routes users to specific endpoints based on their geographic location.
• MultiValue: Returns multiple healthy endpoints for a DNS query, allowing the client to choose.
• Subnet: Routes users to specific endpoints based on their IP address subnet.

Endpoints

An endpoint can be any publicly addressable service. This can include:

• Azure services (e.g., App Services, Virtual Machines, Cloud Services)
• External services hosted outside Azure

Health Probes

Traffic Manager continuously monitors the health of your endpoints using configurable health probes. If an endpoint becomes unhealthy, Traffic Manager automatically stops sending traffic to it and directs users to an available healthy endpoint.

How Traffic Manager Works

When a client requests a resource hosted by your application:

1. The client's DNS resolver queries for the DNS record of your service (e.g., myapp.trafficmanager.net).
2. The Azure DNS service intercepts this query and forwards it to Traffic Manager.
3. Traffic Manager evaluates the configured traffic-routing method and the health of the available endpoints.
4. Traffic Manager returns a DNS response containing the IP address of the selected endpoint.
5. The client's DNS resolver receives the IP address and directs the client's request to that endpoint.

Scenarios and Benefits

• High Availability: Ensure your application is always accessible by automatically failing over to healthy endpoints during outages.
• Improved Performance: Route users to the closest datacenter for reduced latency.
• Disaster Recovery: Distribute your application across multiple regions for robust disaster recovery strategies.
• Maintenance: Gracefully take endpoints offline for maintenance without impacting user experience.
• Hybrid Cloud Solutions: Load balance traffic between Azure and on-premises endpoints.

Example: Setting up a Priority Routing Method

To set up a priority routing method for high availability:

1. Create a Traffic Manager profile in the Azure portal.
2. Configure the "Priority" routing method.
3. Add your primary endpoint (e.g., App Service in West US).
4. Add a secondary endpoint (e.g., App Service in East US) with a higher priority number (lower priority).
5. Configure health probes to monitor the availability of both endpoints.

If the primary endpoint fails, Traffic Manager will automatically direct traffic to the secondary endpoint.

Configuration Snippet (Conceptual)

<TrafficManagerProfile>
    <Name>MyWebAppTraffic</Name>
    <RoutingMethod>Priority</RoutingMethod>
    <Endpoints>
        <Endpoint>
            <Name>PrimaryWebApp</Name>
            <Type>AzureAppService</Type>
            <Location>West US</Location>
            <Priority>1</Priority>
            <HealthProbe>
                <Protocol>HTTP</Protocol>
                <Port>80</Port>
                <Path>/</Path>
            </HealthProbe>
        </Endpoint>
        <Endpoint>
            <Name>SecondaryWebApp</Name>
            <Type>AzureAppService</Type>
            <Location>East US</Location>
            <Priority>2</Priority>
            <HealthProbe>
                <Protocol>HTTP</Protocol>
                <Port>80</Port>
                <Path>/</Path>
            </HealthProbe>
        </Endpoint>
    </Endpoints>
</TrafficManagerProfile>
        

Conclusion

Azure Traffic Manager is a powerful and essential tool for building resilient, performant, and globally available applications on Azure. By leveraging its various traffic-routing methods and health monitoring capabilities, you can ensure a seamless experience for your users, regardless of their location or network conditions.

For more detailed information and advanced configurations, please refer to the official Azure Traffic Manager documentation.