A survey of five plugin OTel plans (datasette-paper, -agent, -litestream,
-accounts, -cron) found every one hand-copying the same core machinery:
the registry classes, the conformance-test harness, the pytest fixtures,
the bucket boundaries and the detached-root-with-Link recipe. This makes
that machinery importable instead:
- The registry classes are documented public API. Attribute gains
values= (a closed enum the conformance helpers enforce - what makes an
attribute safe as a metric dimension); SpanName gains prefix=True for
span families like "chat {model}" whose names share a fixed prefix,
matched by span_for() after exact names. span_for()/attribute helpers
accept a spans= tuple so plugin registries can use them.
- datasette.telemetry.linked_root_span_kwargs(): the root-span-with-Link
shape for work a request caused without containing - background jobs,
scheduled ticks, block=False writes. Core's own write thread now uses
it instead of building the kwargs inline.
- datasette.telemetry_testing: the session provider fixtures, otel_spans
/ otel_metrics, a two-way registry conformance checker (including enum
and prefix handling, filtered by instrumentation scope) and an
assert_package_never_imports_sdk() guard. Core's conftest now imports
these instead of defining them, so the suite consumes the kit exactly
as a plugin's would.
- New "Telemetry for plugin authors" docs page: scope discipline,
registry usage, privacy/cardinality rules, named-callable guidance,
request_span(), the background root-with-link convention (one root per
tick, always emitted), provider-ordering facts and known caveats.
request_span() is now documented public API.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012U7coQfVu8nK2R4q2mCULA
Both histograms declared unit="s" but inherited OpenTelemetry's default
boundaries, which are tuned for milliseconds - so every SQLite query
landed in the single (0, 5] second bucket and every quantile query
returned noise.
The boundaries are the semantic conventions' recommended set for
db.client.operation.duration plus 0.0001 and 0.0005 at the bottom, since
SQLite is in-process and many real queries take tens of microseconds.
(Adapted from 024f2029: that commit assumed the metrics were already in
telemetry_registry.py, which on this lineage held spans only - so this
commit also brings the MetricName registry machinery, the registry
entries for all eight phase-3 metrics, the cog-generated Metric
reference in internals.rst, and the datasette.operation attribute. The
template and facet histograms it also touched belong to phase 5 and are
not included.)
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01F2h9ANGZ7paWSpqs5DUAcG
