Confirmed via packet capture: a Yealink phone and (per RouterOS's known
default behavior) the fleet's routers send classic BSD-style syslog,
not RFC5424. Alloy's loki.source.syslog defaults to RFC5424-only and
was silently dropping every message ("expecting a version value in the
range 1-999"). syslog_format = "rfc3164" fixes it, but that argument
only exists from Alloy v1.5.0 onward (confirmed empirically against
v1.4.3, which fails config load) — bump the pin accordingly. v1.5.0 is
an adjacent minor release, not the kind of large version jump that hit
the Loki/Grafana :latest kernel-incompatibility bug fixed earlier.
:latest images (loki 3.7.3/go1.26.4, presumably grafana/alloy too) reset
every TCP connection on this host — kernel is 5.16.7 (Fedora 35, EOL
since 2023), too old for whatever the newer Go toolchains need.
Confirmed via a disposable grafana/loki:2.9.8 test container: same
config, same host, works cleanly. Pin all three images to older stable
releases instead of chasing this again on every redeploy.
Also fixes an unrelated config bug: instance_addr belongs directly
under `common:`, not nested under `common.ring:` — the misplaced field
was silently ignored, which didn't help but wasn't the actual cause.
Alloy receives syslog on 514/udp and 1514/tcp from network devices,
forwards to a local Loki instance; Grafana provisioned with Loki as
default datasource. Compose bind-mounts config from
/mnt/containers/logging/... on the host (staged separately) since
Portainer's GitOps pull only fetches the compose file, not the repo's
other files.
pipistrello