Maintenance: Thread-safety for Metrics Utility

[phipag]

Summary

The Metrics utility can be used from within the parallel batch processor. The current operating model is:

• Create Metrics singleton using MetricsFactory or MetricsBuilder
• Use it from anywhere within your Lambda handler
• Flush once when the handler finishes (or max batch size is reached)

The problem in multi-threaded scenarios is that metrics configurations such as dimensions / metadata or similar will leak across threads even when flushing manually from within a thread.

Why is this needed?

This is needed to propose the expected thread-safety quality bar to customers.

Which area does this relate to?

Metrics

Solution

Use InheritableThreadLocal to manage Metrics instances.

Acknowledgment

• This request meets Powertools for AWS Lambda (Java) Tenets
• Should this be considered in other Powertools for AWS Lambda languages? i.e. Python, TypeScript

[phipag]

Resolved by #2294