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[bot]]

RN-421

[lucas-zimerman]

Not sure if it's a good candidate, but since hybrid SDKs uses bridges to communicate, we could study if we can get a metric from React Native Bridge Pressure, maybe the data that we can gather from it is how busy it is (how many incomplete calls the bridge has) or the average response time from the bridge. Although in this case, it would be nice if the Native SDKs had support for metrics so we don't create noise with the bridge.

[lucas-zimerman]

We should focus on metrics that are exclusively to React Native, general JavaScript metrics will be collected from the JavaScript SDK whereas Native ones from the native SDKs (we can start those and then port it to the native SDKs later)