117 lines
6.4 KiB
Markdown
117 lines
6.4 KiB
Markdown
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# iDRAC monitoring: Redfish → SNMP migration (design)
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**Date:** 2026-06-05
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**Status:** approved (Viktor) — SNMP primary + thin Redfish remnant
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**Stack:** `stacks/monitoring`
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## Problem
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The R730 iDRAC Redfish exporter (`idrac-redfish-exporter`, mrlhansen
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`idrac_exporter`, image `viktorbarzin/idrac-redfish-exporter:2.4.1-voltage-fix`)
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is configured `metrics: all: true`. It collects on-demand and walks every
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Redfish subtree, making dozens of sequential ~1–2 s requests to a slow BMC.
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Measured live (Prometheus `scrape_duration_seconds{job="redfish-idrac"}`, 24 h):
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- **avg 18.5 s, peak 28.3 s**, occasional fast-fail 0.085 s.
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- Pinned to a **3 m interval / 45 s timeout** because it cannot run at the 2 m
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global cadence.
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The cost is dominated by walks that feed **dashboard-only** panels (`memory`
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10 DIMMs, `network`, `events`/SEL); the operationally important metrics (fan
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speed, temps, power, voltage) come from cheap single-request collectors.
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## Decision
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Make **SNMP the fast primary source** and keep a **thin, slow Redfish remnant**
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for the few things SNMP cannot serve. SNMP walks are fast (the `snmp-ups` job
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runs at 30 s); the iDRAC SNMP agent is already enabled and reachable.
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Rejected alternatives: (1) pure collector-trim of Redfish — still BMC-bound and
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slow; (2) pure SNMP / retire Redfish — would require re-pointing the **external
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ha-sofia** `sensor.r730_fan_speed` REST sensor (collides with a live session
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editing the fan dashboard) and would drop two cosmetic panels.
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## Key findings (ground-truthed)
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- **The `snmp-idrac` job was dead.** It specified **no `module`** param, so
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`snmp_exporter` defaulted to `if_mib` and returned only the iDRAC NIC's
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interface counters — zero health/power/thermal. Both iDRAC jobs relabel to
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`r730_idrac_*`, which hid this. The alert `iDRACSNMPMetricsMissing` is
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**misnamed** — its expr `absent(r730_idrac_idrac_system_health)` checks a
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*Redfish* metric.
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- **A generated `dell_idrac` module already exists**, unmounted, in
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`prometheus_snmp_chart_values.yaml` (~lines 79–1628). The mounted config is
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`ups_snmp_values.yaml` (huawei/if_mib/ip_mib only). iDRAC SNMP = v2c,
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community `Public0` (already the `public_v2` auth in `ups_snmp_values.yaml`).
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- **Live snmpwalk (Public0, 192.168.1.4) confirms** these return real data:
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fan RPM `coolingDeviceReading` (.4.700.12.1.6 = 7080 RPM), temps
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`temperatureProbeReading` (.700.20.1.6, tenths-°C), system watts
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`amperageProbeReading` (.600.30.1.6 = 252 W), PSU input voltage
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`powerSupplyCurrentInputVoltage` (.600.12.1.16), PSU watts/health, global
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health `globalSystemStatus` (.5.2.1), `systemState*` rollups (.200),
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`physicalDisk*` status, `memoryDevice*` size/status/type/speed (.1100),
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`networkDevice*` status/connection (.1100.90), BIOS `2.19.0` (.300.50.1.8),
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model/service-tag (.5.1.3).
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- **Genuine SNMP gaps — but inert or cosmetic today:**
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- SSD life-left % (`physicalDiskRemainingRatedWriteEndurance` .49) → returns
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`255` (N/A) for every drive incl. the Samsung SSD. **Redfish today reports
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`0`** on the one drive that has it, and the SSD-wear alerts guard on `> 0`,
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so they **already never fire** → no functional loss.
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- SEL event log (`5.5.2`) → `NoSuchObject`. The `idrac_events_log_entry`
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metric is **already empty in Prometheus** today → no loss.
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- Indicator LED (`5.1.4`) → absent. Cosmetic ("Off") panel.
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- NIC link-speed Mbps → no OID (health + up/down preserved). Cosmetic.
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- Average watts → no native OID; reconstruct via PromQL `avg_over_time()`.
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Conclusion: **every metric with real, used data today has an SNMP equivalent.**
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## Naming / enum strategy
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`snmp_exporter` names metrics after MIB objects (`temperatureProbeReading`,
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`coolingDeviceReading`, `globalSystemStatus`, …) → after the `r730_idrac_`
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relabel they are `r730_idrac_<mibName>`, different from today's
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`r730_idrac_idrac_*` / `r730_idrac_redfish_*`. **Re-point consumers** (not
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alias): aliasing via `metric_relabel_configs` only renames `__name__` and
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cannot fix the label-set mismatch (Redfish `member_id`/`name` vs SNMP numeric
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indexes) nor the **enum-value mismatch** (DellStatus `3=OK` vs Redfish `1`;
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`systemPowerState 4=on` vs Redfish `2`). Alert exprs must change regardless, so
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re-pointing is the honest path. The module adds `lookups:` so SNMP series carry
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human labels (probe/fan location, disk display name) like today.
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## Consumed-metric → SNMP mapping (DIRECT / REGEN / remnant)
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REGEN = OID returns data but must be added to the module walk.
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| Consumed (today) | Source after migration |
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|---|---|
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| fan health | REGEN `coolingDeviceStatus` .700.12.1.5 |
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| consumed watts | DIRECT `amperageProbeReading` (System Board Pwr Consumption) |
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| system health rollup | DIRECT `globalSystemStatus` .5.2.1 |
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| PSU health | DIRECT `powerSupplyStatus`/`powerSupplySensorState` |
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| memory health | DIRECT `systemStateMemoryDeviceStatusCombined` .200.10.1.27 |
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| storage drive health | DIRECT `physicalDiskComponentStatus` .5.5.1.20.130.4.1.24 |
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| **SSD life %** | **remnant** (SNMP=255 N/A; already inert) |
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| system power state | DIRECT `systemPowerState` .5.2.4 (enum 4=on) |
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| PSU input voltage | DIRECT `powerSupplyCurrentInputVoltage` .600.12.1.16 |
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| system health (absent-probe) | DIRECT `globalSystemStatus` |
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| **fan speed RPM (HA)** | DIRECT via remnant (HA reads exporter directly); SNMP REGEN `coolingDeviceReading` for Grafana |
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| temperature | DIRECT `temperatureProbeReading` .700.20.1.6 (÷10) |
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| avg watts | PromQL `avg_over_time(amperageProbeReading)` |
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| **SEL log** | **remnant** (already empty) |
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| machine/bios info | REGEN model/svctag .5.1.3, BIOS .300.50.1.8 |
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| memory size / cpu count | DIRECT `memoryDeviceSize` (sum) / `processorDeviceStatus` (count) |
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| **indicator LED** | **remnant** (cosmetic) |
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| storage drive info/health/capacity | DIRECT `physicalDisk*` |
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| memory module info/health/cap/speed | DIRECT(size) + REGEN(status/type/speed .1100.50.1.{5,7,8,15}) |
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| network port health/link / **Mbps** | REGEN `networkDevice*` (.1100.90); **Mbps → remnant/drop** |
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| PSU output/input/capacity watts | DIRECT `powerSupplyOutputWatts`/`RatedInputWattage` |
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## Remnant role
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The Redfish exporter stays alive (so the external ha-sofia
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`sensor.r730_fan_speed` REST poll is **unchanged** — no ha-sofia edit, no
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collision). It is trimmed to `sensors,system,network,storage,events` and its
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Prometheus scrape slows to 10 m, keeping **only** the gap metrics (indicator
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LED, NIC Mbps, SSD-life, SEL) via `metric_relabel_configs` to avoid duplicate
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series with SNMP.
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