43 lines
2.6 KiB
Markdown
43 lines
2.6 KiB
Markdown
## Connection pool blocking period for Azure SQL databases is removed
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### Scope
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Minor
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### Version Introduced
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4.6.2
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### Source Analyzer Status
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Investigating
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### Change Description
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Starting with the .NET Framework 4.6.2, for connection open requests to known Azure SQL databases (*.database.windows.net, *.database.chinacloudapi.cn, *.database.usgovcloudapi.net, *.database.cloudapi.de), the connection pool blocking period is removed, and connection open errors are not cached. Attempts to retry connection open requests will occur almost immediately after transient connection errors. This change allows the connection open attempt to be retried immediately for Azure SQL databases, thereby improving the performance of cloud-enabled apps. For all other connection attempts, the connection pool blocking period continues to be enforced.
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In the .NET Framework 4.6.1 and earlier versions, when an app encounters a transient connection failure when connecting to a database, the connection attempt cannot be retried quickly, because the connection pool caches the error and re-throws it for 5 seconds to 1 minute. For more information, see [SQL Server Connection Pooling (ADO.NET)](https://msdn.microsoft.com/en-us/library/8xx3tyca(v=vs.110).aspx). This behavior is problematic for connections to Azure SQL databases, which often fail with transient errors that are typically recovered from within a few seconds. The connection pool blocking feature means that the app cannot connect to the database for an extensive period, even though the database is available and the app needs to render within a few seconds.
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- [ ] Quirked
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- [ ] Build-time break
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### Recommended Action
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If this behavior is undesirable, the connection pool blocking period can be configured by setting the `P:System.Data.SqlClient.SqlConnectionStringBuilder.PoolBlockingPeriod` property introduced in the .NET Framework 4.6.2. The value of the property is a member of the `T:System.Data.SqlClient.PoolBlockingPeriod` enumeration that can take either of three values:
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- `F:System.Data.SqlClient.PoolBlockingPeriod.AlwaysBlock`
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- `F:System.Data.SqlClient.PoolBlockingPeriod.Auto`
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- `F.System.Data.SqlClient.PoolBlockingPeriod.NeverBlock`
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The previous behavior can be restored by setting the `P:System.Data.SqlClient.SqlConnectionStringBuilder.PoolBlockingPeriod` property to `F:System.Data.SqlClient.PoolBlockingPeriod.AlwaysBlock`.
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### Affected APIs
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- `M:System.Data.Common.DbConnection.OpenAsync`
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- `M:System.Data.SqlClient.SqlConnection.Open`
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- `M:System.Data.SqlClient.SqlConnection.OpenAsync(System.Threading.CancellationToken)`
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### Category
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Data
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<!--
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### Original Bug
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213479
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-->
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<!-- breaking change id: 160 -->
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