While I call this post “tricks” for deleting a Windows Azure Virtual Machine it really is not a trick. It does require a little deeper understanding of how Windows Azure creates and hosts Virtual Machines in order to use the REST API to delete them.
Let us start with some background. When you use the Windows Azure Portal to create a new Virtual Machine, a hidden service is created for you that will host the virtual machine role. This will allow more than one Role (i.e. Virtual Machine) to be connected to this service to allow for the automatic round-robin of calls made to the exposed ports.
Below is a list of the Services in one of my Azure Account.
Using the REST API to list all Services, I see that not all of the services returned are shown on the screen in the portal. The service named Test0206D is not listed inside the portal.
<Description>Implicitly created hosted service2013-02-07 01:20</Description>
In this case the Description clearly tells us this was created for us and when. When we delete a Virtual Machine, the service will start to show up inside the portal. If you never want to deploy a new Virtual Machine to that service again, it can be deleted. Otherwise, keeping the service allows the DNS Name to be reserved and allows a new Virtual Machine Role to be added to this service at a later point.
In order to Add a new Role (i.e. Virtual Machine) to an existing service, use the From Gallery option to create the Virtual Machine. Then, on step 4, Virtual Machine mode, select the Connect To An Existing Virtual Machine option. You will get a drop down of available options.
This background leads to the reason it might be tricky to delete a Virtual Machine using the REST API.
To Delete a stand-alone Virtual Machine
In an earlier blog post I listed the way to delete a Virtual Machine was to do an HTTP DELETE to the following URL.
While this work, it only works in the case of a strand-alone Virtual Machine. If you do not know if the Virtual Machine is stand-along or attached, do an HTTP GET to the URL above. If you only have one <Role> element than it is a stand-alone Virtual Machine.
To Delete a Virtual Machine that is attached to another Virtual Machine
In order to Delete a Virtual Machine that is part of another service, you need to Remove the PersistentVMRole. This is done by an HTTP DELETE to the following URL.
The service name and virtual machine name are straight forward but the deployment name is tricky. The deployment name is usually the Service Name but it can also be the name of the first virtual machine you put into the service. To find out for sure, do an HTTP GET to the following URL to get the details of the service deployment.
This will return an XML response that looks like the following.
<Deployment xmlns="http://schemas.microsoft.com/windowsazure" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
The Name element is the name of the Deployment.
In summary, a single call can be made to delete a stand-alone Virtual Machine. For scenarios that join several Virtual Machines together inside a single service it takes a deeper understanding of that service’s properties in order to remove a Virtual Machine from that service.
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