Amazon SimpleDB high latency on first request

Question

I'm using SimpleDB in a desktop application (C#, .NET 2.0) and have a problem with high latency.
The first time I make a request to the DB (query, insert values - doesn't matter) I get a response only after about 10-20 seconds. This happens only the first time, the rest of the responses are pretty fast (haven't measured, but under 300ms for sure).
This doesn't happen when I create the DB client, only when I do the first request. Is it normal for authentication to be that slow? (I presume that on the first request authentication is done).

Thanks in advance.

EDIT

When I run the first time something like

SelectResponse response = dbService_.Select(request);

in the output panel I get:

'PhotoExchange.vshost.exe' (Managed (v2.0.50727)): Loaded'C:\Windows\assembly\GAC_MSIL\System.Data.SqlXml\2.0.0.0__b77a5c561934e089\System.Data.SqlXml.dll'
'PhotoExchange.vshost.exe' (Managed (v2.0.50727)): Loaded 'System.Xml.Xsl.CompiledQuery.1'
'PhotoExchange.vshost.exe' (Managed (v2.0.50727)): Loaded 'System.Xml.Xsl.CompiledQuery'
 A first chance exception of type 'System.IO.FileNotFoundException' occurred in mscorlib.dll
'PhotoExchange.vshost.exe' (Managed (v2.0.50727)): Loaded 'rg1d4wjc'  

Is it normal? The FileNotFoundException looks very strange.

Answer 1

Probably there is something wrong with my Windows/.NET installation. I took a sample from the SDK, compiled it (even used NGEN) and got about 30 sec delay on the first request. I copied the same executable to a virtual machine and the delay was 5 seconds. Still pretty big, but it's acceptable.

Answer 2

At a guess, you're building the service client dynamically from the WSDL at runtime - although I'm not sure it should take that long.

Instead you could build this into your project in advance by adding a web service reference in Visual Studio or using svcutil.exe (the equivalent command-line utility).

Answer 3

.NET does Just in time (JIT) compilation (compiles the code when it is first run), theres always a speed penalty on the first iteration (altough 10-20 seconds seems huge).

I have never used them but there are tools like ngen which allows you to compile the code beforehand.

In applications where I cant allow the first iteration to be slow I usually initialize the application by having "dummy" data run through my critical path.

There are probably other causes for the problem, but I would investigate that.

Hopefully that helps

Answer 4

Sounds like something is timing out, then silently failing over to a successful second channel that is then cached for subsequent calls. First suspicion? DNS, probably. I'd check your workstation's TCP/IP settings to see if your Primary DNS server is up, or replace them with Google's Public DNS at 8.8.8.8 and 8.8.4.4

Answer 5

It may be WebProxy detection (I assume the .NET client you are using is just a wrapper around a web service).

See if you can disable/null out the WebProxy property on the WebClient being used by the service wrapper.