fix(observability): Promtail template uses ToLower (capital T) - #51
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Hot-fix for a real regression introduced in commit 716de4e (PR #47, the log/trace correlation work): the Pino-level template was written as `{{ .level | toLower }}` (Sprig-style lowercase), but Promtail's template stage doesn't register Sprig — it only exposes Go's strings.ToLower as a function named `ToLower` (capital T). The result was the Promtail container failed to start with: failed to make Docker service discovery target manager: invalid template stage config: template: pipeline_template:1: function "toLower" not defined …and has been crashlooping in dev / restart-looping in any other deployment since PR #47 landed. Net effect: Loki has been receiving zero log lines for that window — the structured-logging pipeline silently went dark. Fix: capitalised function name + a comment so the same mistake doesn't happen again on future template changes. Verification: `grafana/promtail:3.2.1 -check-syntax` clean, and the container now starts (logs `Starting Promtail` without the function-not-defined error) against this config. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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Hot-fix for a real regression introduced in commit 716de4e (PR #47,
the log/trace correlation work): the Pino-level template was written
as
{{ .level | toLower }}(Sprig-style lowercase), but Promtail'stemplate stage doesn't register Sprig — it only exposes Go's
strings.ToLower as a function named
ToLower(capital T).The result was the Promtail container failed to start with:
failed to make Docker service discovery target manager:
invalid template stage config:
template: pipeline_template:1: function "toLower" not defined
…and has been crashlooping in dev / restart-looping in any other
deployment since PR #47 landed. Net effect: Loki has been receiving
zero log lines for that window — the structured-logging pipeline
silently went dark.
Fix: capitalised function name + a comment so the same mistake
doesn't happen again on future template changes.
Verification:
grafana/promtail:3.2.1 -check-syntaxclean, and thecontainer now starts (logs
Starting Promtailwithout thefunction-not-defined error) against this config.
Co-Authored-By: Claude Opus 4.7 noreply@anthropic.com