Skip to main content

Azure and IP Persistence - VM,Web/Worker Roles

If you already worked with Windows Azure, especially with worker roles, web roles or VM I suppose that you noticed that Azure don’t guaranty a static IP of this machines. Because of this it is not recommended to access or connect different Azure resources based on the IP (internal IP).
But in the same time, there are moments when the IP is persisted. For example when you restart the resource. In this blog post I will try to explain when the IP of the resources will not change and will remain the same after different actions.

Case: Upgrade
Let’s suppose that our resource is restarted after an update. In this case the original IP of it will be persisted.
Example:
Before:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11 (restarted)
After:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11

Case: Hardware fail
When we have a resource that I take down because of different situations (for example hardware fail) the original IP of the machine will be persisted after the instance is re-deployed. Even if the instance is moved on a different physical device.
Example:
Before:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11 (hardware fail)
After:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11

Case: Resource reboot
In the moment when a resource is rebooted the original IP will be persisted.
Example:
Before:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11 (reboot)
After:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11

Case: Scale up with a new image
When we need to scale up, allocating a new image of our resource a new IP will be allocated to this resource. The existing images will remain with the same IP as before.
Example:
Before:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11
After:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11
VM_IN_2 – 10.0.0.11

Case: Scale up after a scale down
After a scale up and a scale down, the next operation of scale up will not create a new image of the resource with the same IP as last time when we scale up.
Example:
Before:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11
Scale up:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11
VM_IN_1 – 10.0.0.12
Scale down:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11
After (scale up second time):
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11
VM_IN_2 – 10.0.0.13

Case: Resource is de-allocated (stop de-allocate)
When we have a resource that is de-allocated we cannot assume that the current IPs will be persisted until the resource will be allocated again. Allocating the resource again will use different IPs
Example:
Before:
VM_IN_0 – 10.0.0.10
VM_IN_1 – 10.0.0.11
De-allocate
After (allocate resource again):
VM_IN_0 – 10.0.0.12
VM_IN_1 – 10.0.0.13

If we have situations when the IP of the resource is the same, there is another story with MAC address. Don’t assume that if the IP will be the same, than the MAC address will persist also. For example for the hardware fail case, the MAC address will change because another VM will be used.

Comments

Popular posts from this blog

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See http://go.microsoft.com/fwlink/?LinkId=260882 for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

TeamCity.NET 4.51EF 6.0.2VS2013
It seems that there …

How to check in AngularJS if a service was register or not

There are cases when you need to check in a service or a controller was register in AngularJS.
For example a valid use case is when you have the same implementation running on multiple application. In this case, you may want to intercept the HTTP provider and add a custom step there. This step don’t needs to run on all the application, only in the one where the service exist and register.
A solution for this case would be to have a flag in the configuration that specify this. In the core you would have an IF that would check the value of this flag.
Another solution is to check if a specific service was register in AngularJS or not. If the service was register that you would execute your own logic.
To check if a service was register or not in AngularJS container you need to call the ‘has’ method of ‘inhector’. It will return TRUE if the service was register.
if ($injector.has('httpInterceptorService')) { $httpProvider.interceptors.push('httpInterceptorService&#…

Fundamental Books of a Software Engineer (version 2018)

More then six years ago I wrote a blog post about fundamental books that any software engineer (developer) should read. Now it is an excellent time to update this list with new entries.

There are 5 different categories of books, that represent the recommended path. For example, you start with Coding books, after that, you read books about Programming, Design and so on.
There are some books about C++ that I recommend not because you shall know C++, only because the concepts that you can learn from it.

Coding

Writing solid codeCode completeProgramming Pearls, more programming pearls(recommended)[NEW] Introduction to Algorithms

Programming

Refactoring (M. Fowler)Pragmatic ProgrammerClean code[NEW] Software Engineering: A Practitioner's Approach[NEW] The Mythical Man-Month[NEW] The Art of Computer Programming

Design

Applying UML and Patterns (GRASP patterns)C++ coding standards (Sutter, Alexandrescu)The C++ programming language (Stroustrup, Part IV)Object-oriented programming (Peter Coad)P…