fix: Support provisioned concurrency in cold start detection

[dcabib]

Summary

Fixes #2113 - Provisioned concurrency not considered in Logging and Metrics

Problem

When Lambda functions use Provisioned Concurrency, AWS sets AWS_LAMBDA_INITIALIZATION_TYPE=provisioned-concurrency to indicate pre-warmed environments. However, Powertools incorrectly reported these as cold starts across all utilities:

• Logging: cold_start: true in JSON logs
• Metrics: Emitted ColdStart metric with value 1
• Tracing: ColdStart: true annotation in X-Ray segments

Solution

Updated the centralized cold start detection logic in LambdaHandlerProcessor.isColdStart() to check for the AWS_LAMBDA_INITIALIZATION_TYPE environment variable.

Changes

• LambdaConstants.java: Added constants for AWS environment variables
• LambdaHandlerProcessor.java: Enhanced isColdStart() method to detect provisioned concurrency

Evidence

Before Fix (Bug):

{"level":"INFO","message":"Handler Event","cold_start":true,"service":"triage"}

ColdStart metric emitted: "ColdStart":1.0

After Fix (Resolved):

{"level":"INFO","message":"Handler Event","cold_start":false,"service":"triage"}

No ColdStart metric emitted

Testing

• ✅ Deployed to AWS with provisioned concurrency
• ✅ Reproduced original bug in CloudWatch logs
• ✅ Applied fix and verified resolution
• ✅ All three utilities (Logging, Metrics, Tracing) now work correctly

Impact

• Centralized Fix: Single change fixes all utilities
• Backward Compatible: Preserves existing behavior
• AWS Standard: Uses official AWS environment variable

[sdangol]

@dcabib There's an issue in the SonarQube finding, can you look into that.

[dcabib]

@sdangol Issue fixed.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[dreamorosi]

Right now we're explicitly comparing the AWS_LAMBDA_INITIALIZATION_TYPE to this value provisioned-concurrency and returning false in the isColdStart() method.

As documented here, there are other types of initialization types during which isColdStart() should return false (hint snap-start).

A better and more future proof approach would be to instead check if the initialization type is on-demand and if it is, maintain a logic similar to the existing one, if it's not, always return false.

[dcabib]

Hey @dreamorosi, thanks for the feedback! I've cleaned up the PR - removed the SonarCloud changes, took out the unrelated provisioned concurrency stuff that belongs in #2124, fixed the license header, and kept it focused just on CRaC tracing. The SpotBugs exclusions are there because CRaC beforeCheckpoint methods intentionally ignore return values during priming. Should be good to go now!

[dreamorosi]

Hi, I see you've missed/ignored the review feedback that I left here and instead left a comment for a completely different PR.

While we're open to contributors, we also need to mindful of our team's time and misusing reviewers time is not appropriate.

Thank you, but I'll close this PR.