Identify auto-collected metrics (no tracing overlap)

[dingsdax]

We want to define a set of lightweight metrics that SDKs can automatically collect for e.g. framework, language or platform, focusing only on signals that do NOT overlap with Tracing. Ideally these metrics should give a quick sense of app or runtime health, … while deeper investigation will still rely on traces or profiles.

Examples:

• Node.js runtime metrics (e.g., event loop delay, heap usage)
• Prisma-related metrics in Next.js
• Mobile CPU / memory usage to help surface potential ANRs or app hangs

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Candidate Metrics (add more below)

• …

(please also add ideas, questions or examples in comments)

[linear]

JS-1262