Skip to main content

Windows Azure Storage and Read-Access Geo Redundant Feature (Part 2)

Part 1
In the last post we describe the new feature of Windows Azure Storage that give us the possibility to not only replicate the storage content to another datacenter, but also access in in read-only mode when the primary storage is down - Read Access Geo Redundant Storage (RA-GRS)
In this post we’ll talk about some things that we should be aware when we are staring to use RA-GRS.

Retry Policy
First thing that we need to be aware is the retry policy. With geo redundant feature we need another retry policy that can automatically fall back to the second account when the first down cannot be accessed.
For this purpose a new interface was created called “IExtendedRetryPolicy” was created. This new interface comes with a method called “Evaluate” that detect if the operation should be retried or not. Because we have two storage accounts that needs to be checked there is a small change in behavior. We need a mechanism to switch the two accounts and also to take into the consideration the time interval.
For this behavior we have already an implementation “ExponentialRetry” and “LiniarRetry” that take into account all this things. If you have time you can look over the implementation here: https://github.com/WindowsAzure/azure-storage-net/tree/master/Lib/Common/RetryPolicies.
The retry policy is set through Options of different requests or through the client itself.
CloudBlobClient bc = sa.CreateCloudBlobClient(...)
bc.RetryPolicy = new LiniarRetry();
...
OR
BlobRequestOptions bro = new BlobRequestOptions()
{
  RetryPolicy = new LiniarRetry(),
  ServerTimeout TimeSpan.FromMinutes(1),  
};
CloudBlockBlob blob = container.GetBlockBlobReferecen("FooName");
blob.DownloadFile( fileName, FileMode.OpenOrCreate, null, bro );
...
TableRequestOptions tro = new TableRequestOptions()
{
  RetryPolicy = new LiniarRetry(),
  ServerTimeout TimeSpan.FromMinutes(1),  
};
...
QueueRequestOptions tro = new QueueRequestOptions()
{
  RetryPolicy = new LiniarRetry(),
  ServerTimeout TimeSpan.FromMinutes(1),  
};

Location Mode
In the last post we talk about this property, but when we should set this value? This value should be set at the request option object. There we have a property called LocationMode that will allow to do this.
CloudBlobClient bc = sa.CreateCloudBlobClient(...);
bc.LocationMode = LocationMode.SecondaryOnly;
In this example if the primary account is down (404) or we have a timeout expectation, that a fallback to the second account is made.

In this post we saw how we can change the retry policy when we use the Read Access Geo Redundant Storage.

Comments

Popular posts from this blog

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&#…

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 …

Run native .NET application in Docker (.NET Framework 4.6.2)

Scope
The main scope of this post is to see how we can run a legacy application written in .NET Framework in Docker.

Context
First of all, let’s define what is a legacy application in our context. By a legacy application we understand an application that runs .NET Framework 3.5 or higher in a production environment where we don’t have any more the people or documentation that would help us to understand what is happening behind the scene.
In this scenarios, you might want to migrate the current solution from a standard environment to Docker. There are many advantages for such a migration, like:

Continuous DeploymentTestingIsolationSecurity at container levelVersioning ControlEnvironment Standardization
Until now, we didn’t had the possibility to run a .NET application in Docker. With .NET Core, there was support for .NET Core in Docker, but migration from a full .NET framework to .NET Core can be costly and even impossible. Not only because of lack of features, but also because once you…