re: Changes in Windows Azure Storage Client Library – Windows Azure SDK 1.3

Jai Haridas (MSFT) — Fri, 03 Dec 2010 16:55:55 GMT

Hi Peter,

I understand that this indirection is relatively little more work than defining them as constants in a file, but following this pattern allows you to continue purging your data efficiently and in addition decouples your application logic from Windows Azure Storage service's GC process.

There are various scenarios where this fits is quite well:

1> Scenario: Container for files that need to be purged periodically

Create a container/table for say every month example: News_Nov_2010. This way when you want to purge the data, you still need just one call to delete the container. The application always forms the container name using the current month and year and can set this to change based on a timer.

2> Scenario: Testing environments

The account/container/table names can come from configuration files/Tables. Maintain separate files for Test vs. Production environments. If configuration file is used, then you can check-in the new names into your source control. If the list is maintained in a table, one option is to run a script that goes and creates the new tables before updating the configuration table with the new names. During initialization phase, your application will read this configuration and set the table names to use.

As for the CreateTableIfExists, you would need to handle exceptions. Here is some very trivial code:

try

{

bool isCreated = client.CreateTableIfNotExist(containerName);

}

catch (StorageException e)

{

Log("Exception: {0}, {1}-{2}",

e.ErrorCode,

e.ExtendedErrorInformation.ErrorCode,

e);

// We could have some errors here like TableBeingDeleted and since the container is not created, we cannot continue.

throw;

}

catch (Exception e)

{

Log("Table Exception: {0}", e);

throw;

}

If required, you can wrap the above code in a retry of your own: on an exception, wait for 40 seconds and retry. Retry at most X times (where X is based on how much your application can wait during initialization).

Thanks,

Jai

re: Changes in Windows Azure Storage Client Library – Windows Azure SDK 1.3

Peter Kellner — Wed, 01 Dec 2010 18:44:49 GMT

Thanks for the improvements.

I'm still confused on #3, CreateIfNotExist. It would help me if you would show an example (best practices) for achieving the functionality "CreateIfNotExist", even if that means somehow check to see if it exists, then create. This point has created a bunch of forum questions (including by me) and the answer above (don't do it, create another name) is not very satisfying. The name I use has meaning and I don't want to create another level of redirection in creating a new container name that I have to track someplace else.