Amazon SimpleDB 首次请求时出现高延迟
我在桌面应用程序（C#、.NET 2.0）中使用 SimpleDB，并且遇到高延迟问题。
第一次向数据库发出请求（查询、插入值 - 无关紧要）时，我仅在大约 10-20 秒后收到响应。这种情况只发生在第一次，其余的响应都相当快（尚未测量，但肯定低于 300 毫秒）。
当我创建数据库客户端时，这种情况不会发生，只有当我执行第一个请求时，才会发生这种情况。认证这么慢正常吗？ （我认为在第一次请求时身份验证已完成）。
提前致谢。
编辑
当我第一次运行类似
SelectResponse response = dbService_.Select(request);
输出面板中的内容时，我得到：
'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'
这正常吗？ FileNotFoundException 看起来很奇怪。
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.
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听起来好像有些东西超时了，然后默默地故障转移到成功的第二个通道，然后缓存该通道以供后续调用。第一个怀疑？ DNS，可能是。我会检查您工作站的 TCP/IP 设置，看看您的主 DNS 服务器是否已启动，或者将其替换为 Google 的公共 DNS，地址为 8.8.8.8 和 8.8.4.4
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
它可能是 WebProxy 检测（我假设您使用的 .NET 客户端只是 Web 服务的包装器）。
查看是否可以禁用/清空服务包装器使用的 WebClient 上的 WebProxy 属性。
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.
据猜测，您正在运行时从 WSDL 动态构建服务客户端 - 尽管我不确定它应该花费那么长时间。
相反，您可以通过在 Visual Studio 中添加 Web 服务引用或使用 svcutil.exe（等效的命令行实用程序）提前将其构建到您的项目中。
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).
.NET 进行即时 (JIT) 编译（在代码编译时编译代码）第一次运行），第一次迭代总会有速度损失（尽管 10-20 秒似乎很大）。
我从未使用过它们，但有像 ngen 这样的工具可以让您预先编译代码。
在我不能允许第一次迭代变慢的应用程序中，我通常通过让“虚拟”数据运行我的关键路径来初始化应用程序。
该问题可能还有其他原因，但我会对此进行调查。
希望这有帮助
.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
我的 Windows/.NET 安装可能有问题。
我从 SDK 中获取了一个样本，对其进行了编译（甚至使用了 NGEN），并在第一个请求上得到了大约 30 秒的延迟。我将相同的可执行文件复制到虚拟机，延迟为5 秒。虽然还是蛮大的，不过也可以接受。
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.