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[Instrumentation.AspNetCore, Instrumentation.Http] Cache activity names #1854

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[Instrumentation.AspNetCore, Instrumentation.Http] Cache activity names #1854

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[Instrumentation.AspNetCore, Instrumentation.Http] Cache activity names
joegoldman2 Jun 1, 2024
3cf42c1
Merge branch 'main' into fix/1759
cijothomas Jun 4, 2024
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joegoldman2 Jun 15, 2024
905ff72
Merge branch 'main' into fix/1759
joegoldman2 Jun 15, 2024
aec213e
Get from cache even if the size is exceeded
joegoldman2 Jun 15, 2024
8e4e39f
Merge branch 'main' into fix/1759
joegoldman2 Jun 28, 2024
77319f3
Merge branch 'main' into fix/1759
joegoldman2 Jul 5, 2024
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1 change: 1 addition & 0 deletions opentelemetry-dotnet-contrib.sln
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Expand Up @@ -252,6 +252,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Shared", "Shared", "{1FCC8E
src\Shared\PropertyFetcher.AOT.cs = src\Shared\PropertyFetcher.AOT.cs
src\Shared\PropertyFetcher.cs = src\Shared\PropertyFetcher.cs
src\Shared\RedactionHelper.cs = src\Shared\RedactionHelper.cs
src\Shared\RequestDataHelper.cs = src\Shared\RequestDataHelper.cs
src\Shared\ResourceSemanticConventions.cs = src\Shared\ResourceSemanticConventions.cs
src\Shared\SemanticConventions.cs = src\Shared\SemanticConventions.cs
src\Shared\ServerCertificateValidationHandler.cs = src\Shared\ServerCertificateValidationHandler.cs
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25 changes: 24 additions & 1 deletion src/Shared/RequestDataHelper.cs
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Expand Up @@ -5,6 +5,7 @@

#pragma warning disable IDE0005 // Using directive is unnecessary.
using System;
using System.Collections.Concurrent;
#if NET8_0_OR_GREATER
using System.Collections.Frozen;
#endif
Expand All @@ -20,12 +21,14 @@ namespace OpenTelemetry.Internal;
internal sealed class RequestDataHelper
{
private const string KnownHttpMethodsEnvironmentVariable = "OTEL_INSTRUMENTATION_HTTP_KNOWN_METHODS";
private const int DisplayNameCacheSize = 1000;

// The value "_OTHER" is used for non-standard HTTP methods.
// https://github.com/open-telemetry/semantic-conventions/blob/v1.23.0/docs/http/http-spans.md#common-attributes
private const string OtherHttpMethod = "_OTHER";

private static readonly char[] SplitChars = new[] { ',' };
private static readonly ConcurrentDictionary<string, string> DisplayNameCache = new ConcurrentDictionary<string, string>();
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Should be the size limit for this collection?

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@joegoldman2 - What happens if a service receives huge number of requests with invalid routes?

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@joegoldman2 joegoldman2 Jun 3, 2024 •
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You're right, the dictionary will grow without limit. Let me try to think about a solution.

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My understanding is that there's no built-in "bounded" collection in .NET. While it's possible to implement a custom one, probably by wrapping ConcurrentDictionary with additional checks, I'm not entirely enthusiastic about it. I'm open to suggestions.

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@joegoldman2 - One possible option is to check the Count of items within the dictionary before adding a new item. The Count could be some pre-defined number. If the Count exceeds that number, then we could simply skip adding items to the Dictionary.


#if NET8_0_OR_GREATER
private readonly FrozenDictionary<string, string> knownHttpMethods;
Expand Down Expand Up @@ -84,7 +87,27 @@ public void SetActivityDisplayName(Activity activity, string originalHttpMethod,
var normalizedHttpMethod = this.GetNormalizedHttpMethod(originalHttpMethod);
var namePrefix = normalizedHttpMethod == "_OTHER" ? "HTTP" : normalizedHttpMethod;

activity.DisplayName = string.IsNullOrEmpty(httpRoute) ? namePrefix : $"{namePrefix} {httpRoute}";
activity.DisplayName = GetDisplayName();
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How much performance would it gain? The new method seems to have enough if checks to counter the benefit. Plus the additional memory usage.


string GetDisplayName()
{
if (string.IsNullOrEmpty(httpRoute))
{
return namePrefix;
}

if (DisplayNameCache.TryGetValue(httpRoute!, out var displayName))
{
return displayName;
}

if (DisplayNameCache.Count < DisplayNameCacheSize)
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.Count gets a lock on all buckets, so this won't be efficient on the hot path

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Yes, that's what the benchmark above shows.

{
return DisplayNameCache.GetOrAdd(httpRoute!, $"{namePrefix} {httpRoute}");
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@vishweshbankwar vishweshbankwar Jun 17, 2024 •
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Re-checking - Can two http methods have the same route values?. if that happens, we will incorrectly set the display name here.

e.g.
Put /api/document/{id}
Get api/document/{id}

}

return $"{namePrefix} {httpRoute}";
}
}

internal static string GetHttpProtocolVersion(Version httpVersion)
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