@fougere/observability

One span per operation, and the four signals derived from it Optional in the strong sense: core holds no tracing code at all, only a trace field on the invocation that it carries and never reads. An app that does not install this pays nothing.

extensions: [observability({ service: 'blog', otlp: 'http://localhost:4318' })],

The parent rides the invocation, not a header — so the trace crosses whatever the topology became, and the difference between the two spans of a split call is what the wire cost. Rate, errors and duration are one metric (a histogram of durations, dimensioned by the op and by its verdict); saturation is counted by the middleware. OTLP over HTTP in the JSON encoding — no protobuf, no dependency.

rpc.topology is declared here, not by core: an app that never installed this refuses the op by name, which is the whole degradation a reader needs.

Installation

pnpm add @fougere/observability

Part of Fougere — one schema, a gradient from monolith to distributed, the same user code. Reference documentation: the site (en/fr).