NoSQL engines do not like System.Decimal

Here we are with another discovery to be aware of when you plan to go on the cloud or more in general to use some NoSQL engine: System.Decimal is not supported.

We are making a test drive of 3 NoSQL engines:

• Azure Table Storage: key – value
• Amazon SimpleDB: key – value
• MongoDB: document based

All of them do not support System.Decimal, therefore if you want to store currencies, exchange rates, large amounts with decimal digits, you’ll have to find a workaround. For the POC we have decided to go for double type, but during communications with real POS terminals ISO8583 protocol is used. In it amounts are divided in 2 separate parts:

• Amount: total amount with integer part followed by mantissa without separatore (i.e. 100,91 becomes 10091)
• MinorUnit: number of decimal digits (i.e. considering 100,91 it is 2)

Here follows a short summary table of types supported by the 3 engines:

Tipo	Azure Table Storage	Amazon SimpleDB	MongoDB
byte[]	X		X
bool	X		X
DateTime	X		X
double	X		X
Guid	X		X
Int32 o int	X		X
Int64 o long	X		X
String	X	X (max 1024 bytes)	X
regex			X

Amazon has decided to use a simpler technical implementation for its NoSQL on the cloud, but this lead to some limitations: values are all stored as strings with a maximum size limited to 1024 bytes and comparison is lexicographic, therefore for SimpleDB 10 is before 2, so developers have to do some additional work (losing a bit of performance on application code) to handle numeric values: http://aws.amazon.com/articles/1232

Note: it’s always possible to implement an event handler to be called during reading/writing operation against NoSQL above, to be used to convert Decimal to string and viceversa.

Stay tuned for the next stop!

Azure Queue Service: maximum message size is 8KB or 64KB?

Here we are with a small problem encountered: the maximum size of the Azure Queue has been increased from 8KB to 64KB from version 18.8.2011. Cool! A little more space available is great, especially on messages with lots of metadata to be sent.
But if like me you try to create a message with a size of 10KB using the SDK 1.5 (October 2011), you will receive an error.

Now to figure out exactly where the problem was I used JustDecompile (since the good old Reflector is no longer free, I tried the beta of JustDecompile from Telerik) and I decompiled the CloudQueueMessage by Microsoft.WindowsAzure.StorageClient.dll and … surprise! In the constructor there’s a nice hard-coded limit to 8192 bytes in the MaxMessageSize property:

CloudQueueMessage.MaxMessageSize = (long) 8192;

How to solve the problem? By downloading the 1.6 SDK Azure where the client libraries have been updated with the new limits and the same dll decompiled now has:

CloudQueueMessage.MaxMessageSize = (long) 65536;

Our cloud adventure has begun! Azure and then AWS

Finally we started! A nice proof of concept of a distributed architecture Cloud – OnPremise. First we’ll try Azure and then AWS.
I’ll try to post some of travel notes  of this adventure with problems, advantages, strengths and weaknesses, performance identified in order to help future adventurers.

We’ll try everything a lot of things:

• Azure Table Storage – SimpleDB: as NoSQL to save and retrieve large amounts of data
• Blob Storage – S3 to store large sets of data
• Azure Queue – SQS: for communication between the different roles within the same region
• Azure SQL – MySql: for relational data on the cloud
• SQL Data Sync: to synchronize distributed databases cloud – OnPremise
• Bus Service – SNS + SQS: to use publish/subscribe pattern for data distribution between the region and OnPremise
• Traffic Manager: to automatically balance the client calls to the nearest Azure region
• MongoDB: there will be experiments to compare a NoSQL Document based like MongoDB with the key-value solutions offered by Microsoft and Amazon
• Other: MEF, AutoMapper, AppFabric, Caching, TPL

Let’s start the journey!

Azure Table Storage and the FirstOrDefault operator

Today I’ve lost the whole afternoon fighting against this damn issue so I want to share this with everyone to save your time!

I was performing a simple query against Azure Table Storage using PartitionKey and RowKey in order to retrieve a specific entity in a specific table (i.e.: http://127.0.0.1:10002/devstoreaccount1/Spaceship(PartitionKey=’380′,RowKey=’1234′)).

During tests, the first scenario was where no entities with give PK and RK were present and I was using a simple query ending with FirstOrDefault operator like 

TableRepository.FindWhere(p => p.PartitionKey == entity.Spaceship.CountryCode.ToString() &&
        p.RowKey == entity.SerialNumber).FirstOrDefault();

and I was expecting null but in reality I started to get 404 error with detailed message below:

<error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">
  <code>ResourceNotFound</code>
  <message xml:lang="en-US">The specified resource does not exist.</message>
</error>

After several hours struggling with various tests I discovered following Pearls of Azure Wisdom:

- Internet Explorer can’t be used to query directly table storage account, it does not return results at all, because

- You have to set IgnoreResourceNotFoundException = true in the TableServiceContext in order to receive null when an entity is not found instead of error 404

TF208002 error during editing of Product Planning.xlsm

Product Planning.xlsm of my project was corrupted. At the opening it gave me the error: TF208002: “The name that you specified for the column header is a reserved name for this work item list. Choose a different name and try again.”

Clearly I have tried everything but without success

Solution:

• Take the file directly from Agile 5 Process Template from Microsoft (MSF for Agile Software Developmentv5.0 \ Windows SharePoint Services \ Shared Documents \ Project Management) and copy it to your Project Portal
• Open it and press Edit Workbook
• Go to the Team tab and select Configure -> Server Connection
• Press OK on the popup
• Select your project and press Connect
• Press List and select New Query Product Planning pressing OK
• Save and you have your file again!

Remote programming session Milan-Verona-Seattle

Wow! This is really a distributed pair programming session! 3 dev scattered across 2 cities in Italy and Seattle, sharing desktop with TeamViewer from Windows and MacOS, using skype for the conference call.

Technology breaks any barrier!

Assigning a work item to a group in TFS

During ALM can happen that a specific work item can’t be assigned directly to a single person. A typical sample can be a bug before triage. In cases such this the best is being able to use a group like "BugKillers".

The procedure below enables you to assign work items to groups or to their users.

In order to enable this you have to:

1. open work item type Bug in the specific project
   
2. modify Assigned To field adding ALLOWEDVALUES rule with the list of all TFS groups containing users that can receive a work item assignment. be sure to leave Exclude Groups unchecked
   
3. remove VALIDUSER rule, because this is responsible for not showing groups in the dropdown list of values for Assigned To field
4. save and close

Now if you open a new bug you’ll be able to assign it to groups or directly to their users

I’m now a Microsoft Certified Trainer!

Finally I did it I’m a Microsoft Certified Trainer and on Monday I will deliver my first course: MOC50430 related to TFS 2010 administration!

Team Foundation Server 2010 SP1 Final

SP1 for TFS 2010 has been released together with SP1 for VS 2010 and it contains a lot of bug fixes. For more details: http://support.microsoft.com/kb/2182621

ApplicationServerWorkflowInstanceStore ConnectionString not found by AppFabric

We started using Windows Server AppFabric for a Silverlight/RIA application and had a problem during configuration on one of our server. The problem was that when we opened .xamlx file to check service health we received the following error:

“Cannot find connection string for connection name ‘ApplicationServerWorkflowInstanceStoreConnectionString’”

Solution: After deep investigation we discovered that the issue was due to the fact that AppPool used to host the service was configured with Enable 32-bit applications flag set to true, therefore it was reading a different machine config file (for 32-bit apps), that is not changed by the AppFabric configuration wizard (Bug? By design? I’ll open a Connect ticket). Setting flag to false solved the issue!

Hope this helps