February 14, 2008 at 8:27 am
Does anyone have any experience using query notifications with a high volume of data changes and a large number of subscribers? Anyone know if it scales well?
What's happened is that a outsource company's developer decided (after consultation with his architect) to use query notifications for a project involving a data feed. Unfortunately this is the first I've heard of any of this, so I have very little details.
The developer has 'stress' tested at the volume that's expected for the pilot project, that is 5 users and 5 inserts/sec with the notification on (I assume a subset of) the inserts. He says the desktop he was testing on can handle that load.
If the pilot is a success, we're expecting the usage to increase to around 200 users and 400-500 inserts/sec. The developer hasn't tested at those levels. He said he would, but I doubt he's going to get to it before the pilot goes live (monday)
Should I be panicking at this point?
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
February 14, 2008 at 8:48 am
Is the point of the notification to force refreshes of the data? That's usually what this is for (meaning - notify that the contents of your cache is no good, so go get ther data again).
I don't have any direct experience, but one of my colleagues played with it for a while. Setting the threshold to low means that your cache is almost always invalid, so you'd be better off assuming you don't have anything cached (meaning - just invalidate the cache without checking it and requery). Setting it too high, and well - you're looking at old data....
If that stress test DOES in fact happen, make sure it's not all done on a single box, meaning - make sure that the notifications are done over the wire, and not between a local IIS box (assuming Web application of course) and a local SQL Server. The latency there is substantially different....
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Your lack of planning does not constitute an emergency on my part...unless you're my manager...or a director and above...or a really loud-spoken end-user..All right - what was my emergency again?
February 14, 2008 at 11:01 am
I don't know exactly what the notifications are for. It's for a trading system, so I will guess that its to tell the front end that a price/rate has changed.
Not IIS. It's a client-server app (as far as I know. I'm so far out of the loop, it's not even funny)
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
January 12, 2015 at 10:32 pm
I know this is a very old thread but I am being confronted with a similar proposal, albeit nowhere near the volumes initially, where QNs and Service Broker would be used to notify n-web servers that data has changed meaning a client screen should be pushed new data. Do you remember the outcome of the project or have you worked with QNs and Service Broker since?
There are no special teachers of virtue, because virtue is taught by the whole community.
--Plato
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