Counter-Queue and Counter-Wait Pool Patterns for SaaS Implementations

SaaS or Software as a Service is the upcoming paradigm shift in the IT industry. Everyone is shifting towards converting their offerings to Cloud platforms. Some of the key things in this model are the; 

• Effective utilization of the resources available
• Satisfy as much service requests as possible with the available resources
• High Throughput

 The Counter-Queue Pattern is an attempt to increase the productivity of the SaaS offerings using the real life scenario of Ticket booking counters in the Railways Stations. Like in the booking counters, the service requests will be piled up in the queues available and executed in parallel. Say we plan to have 10 queues; the service requests available in the 10 queues will be executed in parallel. The diagram below pictorially explains the Counter-Queue pattern;

1. Initially, the service requests will be put in the “Input Queue”
2. The queue manager reads the service requests in the “Input Queue” and allocates them to the “Counter Queues” available. Each counter queue will have the max queue size, depending on that, the queue manager allocates the service requests in them
3. Each counter will perform the similar functionality. They will pick up the service requests in their respective counter queues and perform the necessary functionality and put the result in the “Output Queue”

In case, any counter fails; the service requests will be moved back to the end of the “Input Queue” for re-allotment. As you can notice, the problem here is that when any counter fails; SLA of the service requests in those queues will not be met.

The “Counter-Wait Pool pattern” will solve this problem. The below diagram pictorially explains this pattern

1. Initially, the service requests will be piled up in the input queue
2. The queue manager picks the service requests from the “Input Queue” and assigns a sequential number to it and put in the wait pool. There will be a max size set to the wait pool. Depending on that, queue manager will put the service requests in the wait pool.
3. Each counter will have “Next token” display in them. Depending on the number displayed, the service requests will be picked from the wait pool.
4. Once the counter services the request, the result will be put in the “Output Queue”.

As you can notice, here we will not run into the problem of not meeting the SLA of the service requests on any scenario 

Forbidden 403 error while accessing workitems in TFS2010 sharepoint site Dashboard

Sometimes you may experience the "Forbidden 403" error in TFS2010 when you try to access the workitems from Dashboard in Sharepoint site.

Here is the solution for that;
1) Login to the TFS Application server
2) Locate the directory "C:\inetpub\wwwroot\bin"
3) Give Write permission for the users of TFS

Bingo, now you should be able to access workitems from Dashboard.