67 lines
2.1 KiB
Plaintext
67 lines
2.1 KiB
Plaintext
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Making blocking calls to ``++async++`` methods transforms code that was intended to be asynchronous into a blocking operation. Doing so inside an Azure Function can lead to thread exhaustion.
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[frame=all]
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[cols="^1,^1,^1"]
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|===
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|To Do This …|Instead of This …|Use This
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|Retrieve the result of a background task|``++Task.Wait++``, ``++Task.Result++`` or ``++Task.GetAwaiter.GetResult++``|``++await++``
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|Wait for any task to complete|``++Task.WaitAny++``|``++await Task.WhenAny++``
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|Retrieve the results of multiple tasks|``++Task.WaitAll++``|``++await Task.WhenAll++``
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|Wait a period of time|``++Thread.Sleep++``|``++await Task.Delay++``
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|===
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// If you want to factorize the description uncomment the following line and create the file.
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//include::../description.adoc[]
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== Noncompliant Code Example
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[source,csharp]
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----
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public static class AvoidBlockingCalls
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{
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[FunctionName("Foo")]
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public static async Task<IActionResult> Foo([HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequest req)
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{
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// This can lead to thread exhaustion
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string requestBody = new StreamReader(req.Body).ReadToEndAsync().Result;
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// do stuff...
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}
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}
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----
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== Compliant Solution
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[source,csharp]
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----
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public static class AvoidBlockingCalls
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{
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[FunctionName("Foo")]
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public static async Task<IActionResult> Foo([HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] HttpRequest req)
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{
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string requestBody = await new StreamReader(req.Body).ReadToEndAsync();
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// do stuff...
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}
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}
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----
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== See
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* https://msdn.microsoft.com/en-us/magazine/jj991977.aspx[Async/Await - Best Practices in Asynchronous Programming]
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* https://docs.microsoft.com/en-us/azure/azure-functions/performance-reliability#use-async-code-but-avoid-blocking-calls[Improve the performance and reliability of Azure Functions - Scalability best practices]
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* S4462 - a more generic rule about detecting blocking calls to ``++async++`` methods.
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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The implementation should be common with S4462. When implementing, should make sure S4462 will ignore Azure Functions.
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