This is the change that actually lifts the 5 s ceiling. Until now the
millisecond ladder and the Unit type existed but nothing consumed them.
Telemetry.cpp registered ONE histogram view: instrument name pattern "*",
unit exactly "ms", boundaries {1, 5, ..., 1000, 5000}. Verified against the
installed SDK, "*" matches every name and "ms" matches exactly, so that view
governed every beast::insight Event -- all 54 of them, whatever they measure.
Measured on devnet: 24.9% of rpc_size samples and 100% of jobq_updatepaths
samples fell above 5000. A quantile landing in the `+Inf` bucket reads back
as the second-highest edge, so those p95s reported a flat 5000 rather than a
measurement, and the 1 s to 5 s span was a single four-second-wide bucket
that any quantile inside it had to interpolate across.
Replaces it with one view per unit, keyed on the unit an instrument declares:
- `ms` gets kMillisecondBuckets: every representable edge of the collector's
spanmetrics ladder, plus 60 s and 120 s. The extensions are deliberate --
jobq_updatepaths was measured averaging 59,956 ms, which no span
approaches, so parity alone would still censor it.
- `By` gets kByteBuckets, placed from the measured response distribution
(mean 2131 B, half under 1 kB, tail mean bounded at 7538 B).
OTelEventImpl now derives its declared unit AND its description from unit()
instead of hardcoding "Duration in ms"/"ms", so rpc_size exports as
rpc_size_bytes on the byte ladder. rpc-pathfinding's "RPC Response Size"
panel follows the rename; its unit was already decbytes and is now truthful.
Also corrects Phase7_taskList.md, which still specified the 5000 ladder as
"matching SpanMetrics". That was true when written and became false when the
collector ladder was extended on its own -- implementing the plan as written
reproduced the bug, so the spec is where the defect had come to live. The
edges now have exactly one owner and the plan points at it.
beast::insight::Event documents itself as carrying "a millisecond time, or
other integral value", but both backends assumed the first case: the OTel
bridge declared every instrument with unit `ms` and StatsD tagged every
sample `|ms`. One Event does not measure time -- ServerHandler's "size"
records the serialized RPC response length -- so it exported as
rpc_size_milliseconds and inherited the millisecond bucket ladder. A quarter
of its samples landed above that ladder's top edge, and since Prometheus
returns the second-highest edge for a quantile in the `+Inf` bucket, its p95
panel showed a flat 5.00 kB rather than a measurement.
Adds beast::insight::Unit (Millis, Bytes) plus otelUnitCode(), carried on
EventImpl and selectable at makeEvent(). Naming the unit at creation is what
lets a backend pick the export unit and, through it, the bucket ladder.
- Collector gains a virtual makeEvent(name, Unit) whose default delegates to
the millisecond overload, so a collector that cannot act on a unit keeps
working unchanged. NullCollector and the Groups wrapper override it.
- The Groups override matters most: call sites reach a collector through a
Group, so forwarding only the prefixed name would silently drop the unit.
A test covers that hop specifically.
- Event gains notify(std::uint64_t) for non-duration samples, replacing
ServerHandler's `Event::value_type{response.size()}` -- wrapping a byte
count in a std::chrono::milliseconds compiles but reads as a duration to
everything downstream.
- EventImpl::value_type stays std::chrono::milliseconds. Widening it would
change the wire value of every existing StatsD timer, and metrics needing
finer resolution use the OTel-native microsecond instruments.
The StatsD collector deliberately keeps emitting `|ms`: that path is retired
here (its UDP port is commented out of the compose file and the integration
test fails if anything listens on 8125), so changing its wire format would
alter a legacy contract with no consumer and no way to verify it.
The exported name does not change yet -- OTelEventImpl still hardcodes its
unit. That follows with the unit-keyed histogram views.
