Grafana's log-level buttons filter on a field called `level`; no row in
the store has one. The store's name for it is `severity_text`, chosen by
VictoriaLogs' OTLP ingester rather than by us — v1.52.0's
`app/vlinsert/opentelemetry/pb.go` writes it unconditionally and the
ingest parameters have no `_level_field` to rename it with. So the
mapping is made on the reader: the VictoriaLogs datasource, which was
provisioned with no `jsonData` at all, now carries a `logLevelRules`
entry per severity the journald parser can emit.
`logLevelRules` is the datasource plugin's only level-related jsonData
key — there is no field-name setting and no OpenTelemetry preset to
switch on. It is read off `instanceSettings.jsonData` in the plugin's
`datasource.ts` and typed in its `configuration/LogLevelRules/types.ts`,
both recovered from the sourcemap shipped in the pinned artifact
(`grafanaPlugins.victoriametrics-logs-datasource` 0.26.3). Each enabled
rule appends an `OR severity_text:="INFO"`-shaped term to the query a
level button emits, next to the `level:…` term that matches nothing.
A wrong rule here fails silently: Grafana provisions unknown jsonData
without complaint and the buttons go on returning zero rows. The three
ways to get one wrong — a non-literal `enabled`, a non-canonical `level`
spelling, a value that is not the stored text — are recorded at the
binding, and a module-eval arm pins them along with the real failure
mode, a severity added to `nix/journald-severity.nix` and not here.
`Unspecified` is left unmapped on purpose: it is the store's own
rendering of an absent severity and the thing the logs dashboard's "no
severity" panel counts.
Refs #4560
The direction is the part a reviewer cannot check by looking, so it is
asserted at both ends of the table and in both tiers' groups: an inverted
mapping still maps every value to something, and a case that only asks
whether a severity parser exists passes on the exact defect. The reader
that turns a rendered operator list back into a PRIORITY -> name function
lives in lib.nix, since both tiers need it.
The panel is asserted on its query rather than its title, because a panel
that keeps the title and loses the expression renders an empty graph that
looks exactly like zero prioless lines.
The single module-eval derivation forced ~62 full nixosSystem
fixtures live at once to compute its cases list: 10.6GB peak RSS /
5m25s to evaluate, by far the dominant cost in nix flake check.
Splits it into 21 independent checks.module-eval-* derivations
(1-7 fixtures each) sharing builders/helpers via module-eval/lib.nix,
so no single derivation needs more than a handful of fixtures live
at once. A few cases spanning two clusters carry a small duplicated
fixture rather than threading shared state through lib.nix.
