Long live connection OR on-demand connections?

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3.00/5 (1 vote)

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SQL-Server-2008R2

I was assigned to implement a wrapper class to manage DB connections using ADO in unmanaged C++ and then build an application that works as follow:

"I'll have 3 (or maybe more) instances of the application running as a service, each instance has to check if exists any pending submition in the DB each 2s (a pending submition is a program submition [a solution to a given problem] waiting for evaluation), if exists I get and evaluate it, then I update that submition setting the results and deleting it from the pending table. (the range time to evaluate a submition is: 0s > range < ~(5-10)s and an instance never evaluate more that one submition at the same time)."

My problem is:
I have 2 possibles solutions here:
Stablish a connection once I instanciate the application and never close it (close it when I delete the instance, that theorically never will happen.) or open a connection each 2s in order to get the pending submition (if exists any) and close it, then re-open it to update the submition and close it again....
What solution is better and why?

Posted 28-Jun-13 16:46pm

mdarefull

Updated 28-Jun-13 16:48pm

v2

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The_Inventor 29-Jun-13 1:29am

It would depend on available bandwidth and network uptime reliability. Aside from inquiries to either database, your main goal, as stated above, is to write a wrapper to manage DB connections. The best way is to let the 'system' decide. (2s = queues)

And then there is ->http://msdn.microsoft.com/en-us/library/aa231217(v=VS.60).aspx

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KarstenK · Answer 1 · 2013-07-01T04:34:00

Solution 1

It depends on your real time latencies. I would use one open connection, but you need some fallback for the errorcase.

You should consider bigger intervals and than open and close the connection.

All 2 seconds and 24 hours and that 7 days a week???

Do you AND your user REALLY need such small intervals?

Posted 1-Jul-13 4:34am

KarstenK

Comments

mdarefull 1-Jul-13 19:05pm

Yes, the site is an online-judge so it must remains open 24 hours. Because the users may submit a solution any time of the day, it must check por submitions pending to be evaluated periodically.

KarstenK 3-Jul-13 4:13am

In such cases should the clients submit the data and i would favour a webservice to listen for data.

Like that but the other direction:

http://www.codeproject.com/Articles/428200/How-to-invoke-a-Web-Service-from-a-Stored-Procedur

And: in client-server architectrue you REALLY SHOULD clode the connection.