Azure的SQL数据库相关的异常

Question

我在蔚蓝的数据库已经非标准S2 edition.In我的应用程序的日志，我总是看到许多例外这样的格式：

1.

System.Data.SqlClient.SqlException: The client was unable to establish a connection because of an error during connection initialization process before login. Possible causes include the following: the client tried to connect to an unsupported version of SQL Server; the server was too busy to accept new connections; or there was a resource limitation (insufficient memory or maximum allowed connections) on the server. (provider: TCP Provider, error: 0 - An existing connection was forcibly closed by the remote host.) ---> System.ComponentModel.Win32Exception: An existing connection was forcibly closed by the remote host

2.

System.Data.Entity.Core.EntityException: The underlying provider failed on Open. ---> System.InvalidOperationException: Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached

System.Data.SqlClient.SqlException (0x80131904): The client was unable to establish a connection because of an error during connection initialization process before login. Possible causes include the following: the client tried to connect to an unsupported version of SQL Server; the server was too busy to accept new connections; or there was a resource limitation (insufficient memory or maximum allowed connections) on the server. (provider: TCP Provider, error: 0 - An existing connection was forcibly closed by the remote host.) ---> System.ComponentModel.Win32Exception (0x80004005): An existing connection was forcibly closed by the remote host.

我使用SqlAzureExecutionStrategy，因此在重试一些次数后引发这些异常。

我在azure portla上看到不同的性能指标，但看起来他们没问题。

如何识别问题？

Answer 1

我认为你的数据库负载太重，或者你有一些查询仍在运行或者不能放开连接。

我用这个查询查看正在运行什么：

SELECT (SELECT TOP 1 SUBSTRING(s2.text,statement_start_offset/2+1 , 
    ((CASE WHEN statement_end_offset = -1 
    THEN (LEN(CONVERT(nvarchar(max),s2.text)) * 2) 
    ELSE statement_end_offset END) - statement_start_offset)/2+1)) AS sql_statement, 
    s1.* FROM sys.dm_exec_requests s1 
CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS s2 
ORDER BY 1 

看看你是否还有疑问还在这里运行，或者留意在Azure的门户网站的CPU使用率。

S2数据库不是特别好，它会抑制你的请求，所以如果你正在做很多（甚至是小的）请求，它可能会拒绝它们。

您的重试策略也可能导致问题变得更糟，但当它已经被填满时，会向它发出更多请求。如果是这种情况，你可以尝试使用指数后退。

Answer 2

所有这三个可以解释你的连接池设计。您是重新使用连接，还是每次调用数据库打开它自己的连接？你在每个DBContext的末尾关闭连接吗？你是否正在实现任何一种缓存层来减少到你的数据库的往返次数？

这里有一种方法来查看它是否是您的池的问题。从门户转到有问题的数据库，查看资源利用率图，然后点击编辑。

然后从选择列表中添加会话率和工人的百分比，然后点击确定。

如果您的池是一个问题，你会发现，你的会话和工人比例较高，并可能在100％挂的时间。如果你达到100％，你可以被拒绝长达5分钟的新连接，直到目前的会议和工作人员完成或者被杀死。