Investigated why all three prop pods were restart-looping every few
minutes (RESTARTS counts 7–11 in 99m). The trail:
20:53:33.058 [error] Postgrex.Protocol ("db_conn_10") disconnected:
client (:"Elixir.Microwaveprop.PromEx.Poller.5000") timed out
because it queued and checked out the connection for longer than
15000ms
PromEx's Oban queue-depth poller was scanning the oban_jobs table
every 5s and holding an Ecto connection past its checkout timeout.
That starved the rest of the pool, so /health's `SELECT 1` couldn't
acquire a connection inside the 3s liveness probe timeout, the
kubelet's failureThreshold=3 tripped, and SIGKILL landed on the
BEAM. Every replica cycled on the same cadence.
Two fixes:
1. Split /live (no DB) from /health (DB ping). Kubernetes livenessProbe
now points at /live so a saturated Ecto pool can never cascade into
SIGKILL. Readiness still hits /health so a genuine DB outage drains
the pod from Service endpoints gracefully.
2. Turn off the PromEx Oban plugin in prod via the same flag already
used in test. The queue-depth query isn't worth pod instability;
the oban_web dashboard surfaces the same information without
scanning the job table on a timer.
Locked both down with HealthController tests that verify /live never
touches the Repo (no sandbox owner, controller.live/2 called directly,
200 ok) and /health does (sanity query round-trips).
Set OTEL_EXPORTER_OTLP_ENDPOINT on the prop deployment to the cluster
Collector so Phoenix/Bandit/Oban spans export and link up with
downstream prop-grid-rs / prop-hrrr-point-rs traces in Tempo. Without
this the Elixir app fell back to traces_exporter :none and the Rust
worker spans had no parent, leaving the trace graph disconnected.
The stale comment referenced opentelemetry_ecto as the reason export
was off, but that package was never added to mix.exs (only
opentelemetry_phoenix / _bandit / _oban are listed), so the
span-flood concern no longer applies.
Ecto auto-instrumentation created one span per query, so Oban jobs
running thousands of DB ops produced traces with 8k+ child spans.
Tempo's compactor couldn't ingest them — it stalled long enough to
miss heartbeats, got auto-forgotten from the ring, and crash-looped.
The Elixir grpcbox exporter then blew up trying to reconnect.
Stops the cascade: OTLP endpoint removed from prop and prop-backfill
Deployments, opentelemetry_ecto removed from deps, Phoenix/Oban/Bandit
auto-instrumentation retained. Rust workers still export to Tempo.
Shared NFS idx cache at /data/hrrr_idx lets all prop-grid-rs and
hrrr-point-rs replicas deduplicate redundant NOAA S3 idx fetches.
Opt-in via HRRR_IDX_CACHE_DIR; falls back to in-memory-only when unset.
Also scales prop-grid-rs to 3 replicas (no talos5 pinning),
hrrr-point-rs to 2 replicas, and drops hot pod replicas 4→3 so the
physical-host anti-affinity still fits with talos5 cordoned off for
Postgres.
Adds the OTel deps (opentelemetry + exporter + phoenix / ecto / oban /
bandit auto-instrumentation helpers) and attaches them in
Application.start/2 so the existing Phoenix, Ecto, Oban, and Bandit
telemetry events flow as OTLP spans without any call-site changes.
Exporter config is gated on OTEL_EXPORTER_OTLP_ENDPOINT in
config/runtime.exs — set in the k8s manifests to the cluster
collector (otel-collector.observability.svc.cluster.local:4317).
When unset we switch traces_exporter to :none so nothing is shipped;
dev/test stays quiet.
Resource attributes tag spans with service.name=microwaveprop and
service.namespace=prop, matching the Rust workers' attribute shape
so Tempo can group the full hourly chain across both languages.
Both the main prop deployment and the backfill deployment get the
env; backfill is still a full BEAM node running enrichment workers,
so its Oban/Ecto spans are worth seeing too.
