Bug: Metrics concurrency-related exceptions when used in multi-threaded scenarios

[hjgraca]

Expected Behaviour

Metrics should be thread-safe and handle concurrent access without throwing exceptions.

Current Behaviour

1. Collection was modified; enumeration operation may not execute

   • Occurs in LINQ FirstOrDefault operations when metrics collections are modified concurrently
   • Stack trace points to Metrics.cs line 202-203 and MetricDirective.cs

2. IndexOutOfRangeException: Index was outside the bounds of the array

   • Occurs in Dictionary.TryInsert during AddMetadata operations
   • Stack trace: Metadata.cs:line 156 in CustomMetadata.TryAdd(key, value)

Code snippet

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Possible Solution

No response

Steps to Reproduce

The issue manifests when:

• Multiple threads simultaneously call Metrics.AddMetric() and Metrics.AddMetadata()
• High concurrency scenarios

Powertools for AWS Lambda (.NET) version

latest

AWS Lambda function runtime

dotnet8

Debugging logs