Auto Node.js runtime metrics integration

[chargome]

Currently there's no way to get process-level health metrics out of Sentry for Node.js without writing custom instrumentation. We want to add a new opt-in integration nodeRuntimeMetricsIntegration which auto-collects metrics in a loop.

Metrics

Group	Metric	Type
CPU	node.runtime.cpu.user	gauge
	node.runtime.cpu.system	gauge
	node.runtime.cpu.percent	gauge
Memory	node.runtime.mem.rss	gauge
	node.runtime.mem.heap_total	gauge
	node.runtime.mem.heap_used	gauge
	node.runtime.mem.external	gauge
	node.runtime.mem.array_buffers	gauge
V8 Heap	node.runtime.heap.total_heap_size	gauge
	node.runtime.heap.heap_size_limit	gauge
	node.runtime.heap.total_available_size	gauge
	node.runtime.heap.malloced_memory	gauge
	node.runtime.heap.number_of_detached_contexts	gauge
GC	node.runtime.gc.duration	distribution
	node.runtime.gc.count	counter
Event Loop Delay	node.runtime.event_loop.delay.min	gauge
	node.runtime.event_loop.delay.max	gauge
	node.runtime.event_loop.delay.mean	gauge
	node.runtime.event_loop.delay.p50	gauge
	node.runtime.event_loop.delay.p90	gauge
	node.runtime.event_loop.delay.p99	gauge
Event Loop Utilization	node.runtime.event_loop.utilization	gauge
System	node.runtime.system.free_memory	gauge
	node.runtime.system.total_memory	gauge
Process	node.runtime.process.uptime	counter
Heap Spaces (opt-in)	node.runtime.heap.space.size	gauge
	node.runtime.heap.space.used_size	gauge
	node.runtime.heap.space.available_size	gauge
	node.runtime.heap.space.physical_size	gauge

GC metrics tagged by gc_type. Heap space metrics tagged by heap_space.

Open questions

1. Metric name prefix — node.runtime.* vs. nodejs.* (OTel semconv)
2. GC distribution — requires backend confirmation; fallback is separate min/max/mean/p95 gauges
3. Default collection interval — 60s vs. 10–30s, pipeline cost vs. resolution tradeoff
4. Serverless — flush per-invocation instead of on a timer?
5. Cluster mode — runtime_id / process_id attribute needed to disambiguate workers

[linear-code]

JS-1955