Naming

There is exactly one canonical vocabulary: OpenTelemetry semantic conventions. Lowercase, dot-namespaced, described, with units:

http.server.request.duration    ms
db.client.query.duration        ms
queue.job.duration              ms
queue.jobs.processed
system.memory.usage             By
system.cpu.utilization          1      (fraction 0-1)

Prometheus names are derived automatically — dots become underscores and counters get _total:

http_server_request_duration_bucket{le="100"}
queue_jobs_processed_total

Your own metrics

Namespace by domain, most-general first:

orders.created                — not created_orders
checkout.duration             — not time_of_checkout
billing.invoices.overdue      — hierarchy reads left to right

Package authors: prefix with the package domain (queue_autoscale.workers.desired) so dashboards group naturally.

Rules

• Names match [a-z][a-z0-9._]* — invalid names throw at registration.
• A name is one instrument type forever; re-registering orders.created as a histogram after it was a counter throws InstrumentTypeMismatch.
• Declare units in the instrument (unit: 'ms', 'By', '1') rather than in the name; exporters surface them appropriately.
• Label keys follow the same conventions (http.route, tenant.id). Non-conforming characters are sanitized to _ for Prometheus.