As you may have noticed in the Windows Azure developer portal, we recently released a new management API for Windows Azure Traffic Manager. The new API improves Traffic Manager by allowing developers and IT professionals to script interactions with the service and to interface with the service programmatically.
For those of you who aren’t familiar with Windows Azure Traffic Manager, it gives you control of how traffic is distributed between hosted services in different datacenters. Traffic Manager increases the perceived performance of your application by sending customer traffic to the closest datacenter, and it improves reliability by not sending traffic to hosted services that are down.
With the release of the new API, developers now have full access to the management and creation of Traffic Manager policies, including the creation of a profile from scratch. In this post, we’ll walk through how to create, update, and manage profiles using the new API. Documentation for the new Traffic Manager REST APIs can be found here.
Let's look at a typical configuration in the portal to see how we could accomplish the same configuration using the APIs. Before we get started, if you are new to Windows Azure Traffic Manager, I highly recommend reading an overview of how the service works before continuing.
For reference, I have included a screenshot of a configuration I have setup that uses the performance load balancing method to distribute traffic between an application endpoint setup in the North Central US datacenter and the North Europe datacenter.
Figure 1: Traffic Manager Policy Page
The Edit Traffic Manager Policy dialog allows you to configure a Windows Azure Traffic Manager policy in one screen. Behind the scenes there are multiple API calls that create multiple entities on your behalf that represent this policy configuration that you as a developer will need to be aware of.
So how can you accomplish the same configuration programmatically?
Understanding the entities is the first step. The policy represented above consists of a profile with a domain name specified, at least one definition, which in turn consists of the following configuration: load balancing method, DNS TTL, endpoints and a monitoring configuration among other things.
Figure 2: Traffic Manager Entities
Each profile can have multiple definitions associated with it. However, only one definition can be active at a time. Creating multiple definitions is not currently exposed in the portal. It is entirely possible to define multiple distinct definitions and provide the ability to switch between them without rebuilding them.
Figure 3: Create Profile Request Parameters
The Create Profile API requires you to specify a profile name and the Traffic Manager Domain name. The domain name consists of a DNS prefix (host name) and .trafficmanager.net. In the management portal there is not a location for a profile name; this is generated for you when you use the portal. This is not the case when you create the profile programmatically. How the profile name is generated is something important to understand as a developer. When you create a profile from the portal the name is generated by taking the hostname of the domain name you are specifying and appending -trafficmanager-net to it. For example if the domain name you specified was: woodgrove.trafficmanager.net the internal name of the profile would be woodgrove-trafficmanager-net. When creating a profile programmatically the profile name is whatever you pass into the Create Profile API.
Figure 4: Create Definition Request Parameters
Once a profile is created, you can then create a definition using the Create Definition API to specify the rest of your Windows Azure Traffic Manager configuration.
The definition configuration is not as complex as it looks. Defining the monitor consists of specifying the relative path to an HTTP/HTTPS resource that will tell Traffic Manager the health of your application via the returned status code. You may change the port, protocol and the relative path but the remaining settings have to be set to the default values.
Each endpoint consists of the URL to one of the Windows Azure applications that you want managed in the Windows Azure Traffic Manager and a flag indicating whether it is currently enabled or disabled.
The URL specified when creating the Traffic Manager profile (<dnsprefix>.trafficmanager.net) will be mapped to one of the specified endpoints when a DNS name is resolved. Which endpoint is resolved is based on the load balancing method specified (Performance, Failover or RoundRobin).
WoodGroveUS.cloudapp.net could reside in the North Central data center.
WoodGroveEU.cloudapp.net could reside in the North Europe data center.
WoodGrove.trafficmanager.net would be the parent domain name that when resolved would be mapped to one of the data center endpoints.
Figure 5: Update Profile Request Parameters
There can be multiple definitions associated with a profile but only at most one can be active at a time. For a Traffic Manager profile to be active you must enable one of the definitions associated with the profile. You enable a definition by calling the Update Profile API passing in the version that was returned when you called the Create Definition API.
Managing Existing Profiles and Definitions
Beyond the core operations of creating a profile and its associated definitions, the Traffic Manager REST API also supports List Profiles, Get Profile, List Definitions, Get Definition and Delete Profile. These APIs provide full functionality for building an application to manage Windows Azure Traffic Manager configurations.
If you would like to automate the management of your Windows Azure Traffic Manager profiles but you do not want to write code against the REST API to do it we also have an answer for you. We have updated the Windows Azure PowerShell Cmdlets (now version 2.2) to have full support for the Windows Azure Traffic Manager.
Windows Azure Traffic Manager Cmdlets
Here is an example of how you can use PowerShell to create a new profile and definition:
Windows Azure Traffic Manager is a key technology for enabling global and highly available applications. The new REST APIs will allow application developers to build applications that make the management of Traffic Manager a native part of their application. We have also opened the door for automating deployments to Windows Azure customers by exposing this functionality in the new release of the Windows Azure PowerShell Cmdlets 2.2.