Question

I have a Cloud Service and a VM role in Azure set up. My Cloud Service is a simple MVC site running on Server 2012, and the VM is an Ubuntu OS with redis installed on it. How is inter-role communication supposed to work in Azure? (Everything is in the same data center.)

I could set up a public endpoint on the VM, but I would rather not have my redis machine exposed. Is there a proper way to do this? Is the private IP assigned to my VM fixed? If so I can just use that, right?

Answer 1

You have to use the Windows Azure Virtual Network (WAVN) in order to open communication between a Windows Azure Virtual Machine and Windows Azure Cloud Service.

Note that WAVN has explicit requirement for specifying an Affinity Group. So if you don’t have one – you will be able to create when creating the Virtual Network. Now, your cloud service (i.e. your web/worker roles) must be in the same Affinity Group in order to be able to “join” that virtual network. I am not sure whether it is possible to change the Cloud Service’s Affinity group after the service is created. So just create a new cloud service by specifying the Affinity Group where you created your Virtual Network.

Next step is to configure the Virtual Machine to use the Virtual Network you created – it is part of the “From Gallery” process.

Now you need to instruct the Cloud Service (web/worker role). This is done via the .csconfig file for the Cloud project in Visual Studio. There is yet no UI to configure the networking. What you have to include is a NetworkConfiguration section as a direct descendant of Configuration root element:

<NetworkConfiguration>
  <VirtualNetworkSite name="SampleNetwork" />
  <AddressAssignments>
    <InstanceAddress roleName="ContactManager.Web">
      <Subnets>
        <Subnet name="FrontEnd" />
      </Subnets>
    </InstanceAddress>
  </AddressAssignments>
</NetworkConfiguration>

You describe your roles and the virtual network name and subnets where you want your roles to reside.

Fingers crossed, now everything shall be in the same network – the one you created. Name resolution must be generally working, but it is in Preview, so expect issues with that. Now your MVC application can directly make a “call” to your Linux VM. For addressing just use the VM name.

If you want to call the MVC from the Linux VM – you have to address a specific instance of your WebRole.

As for IP Addresses – internal IP address (A.K.A. Direct IP Addresses or DIP) are never fixed! Even when you create the Virtual Network, you can only have DHCP assigned IP Address. And they will be assigned from the pool you specify in your Virtual Network setup.

A good reading on Windows Azure Virtual networks can be found here.