Redfish collector fails with KeyError: 'StorageControllers' when Dell iDRAC exposes a valid Storage resource without that property

[sagittariuslee]

Description

hardware-observer reports:

Failure in calling the Redfish API.

redfish_call_success = 0

Redfish connectivity and authentication are functional. The failure occurs while prometheus-hardware-exporter processes the Dell iDRAC storage collection.

The Dell iDRAC exposes the following Redfish storage members:

/redfish/v1/Systems/System.Embedded.1/Storage/CPU.1
/redfish/v1/Systems/System.Embedded.1/Storage/AHCI.SL.6-1
/redfish/v1/Systems/System.Embedded.1/Storage/AHCI.Embedded.1-1
/redfish/v1/Systems/System.Embedded.1/Storage/AHCI.Embedded.2-1

Three of the resources contain a StorageControllers property, but /Storage/CPU.1 does not.

CPU.1 is nevertheless a valid Redfish Storage.v1_16_0.Storage object. It exposes 16 drives and reports healthy status:

Id: CPU.1
Name: CPU.1
Type: #Storage.v1_16_0.Storage
StorageControllers present: False
StorageControllers: None
Drives count: 16
Health: OK

The exporter currently accesses StorageControllers unconditionally:

storage_controllers_list: List[Dict] = self.redfish_obj.get(
    curr_storage_uri
).dict["StorageControllers"]

This causes:

ERROR Exception occurred while using redfish object: 'StorageControllers'

Traceback (most recent call last):
  File ".../prometheus_hardware_exporter/collector.py", line 1036, in fetch
    redfish_helper.get_storage_controller_data()
  File ".../prometheus_hardware_exporter/collectors/redfish.py", line 306, in get_storage_controller_data
    storage_controllers_list: List[Dict] = self.redfish_obj.get(curr_storage_uri).dict[
KeyError: 'StorageControllers'

Charm revision

latest/stable

Juju version

3.6.13

Cloud

No response

Expected behaviour

A valid Redfish Storage resource that does not expose a StorageControllers property should not cause the entire Redfish collector to fail.

The collector should handle the property being absent and continue processing the remaining storage resources.

Sep 02 18:37:32 dichy0318 python3[2333168]: 2026-09-02 18:37:32 INFO Response Time for GET to /redfish/v1/Systems/System.Embedded.1/Storage/: 0.03355526924133301 seconds.
Sep 02 18:37:32 dichy0318 python3[2333168]: 2026-09-02 18:37:32 INFO Attempt 1 of /redfish/v1/Systems/System.Embedded.1/Storage/CPU.1
Sep 02 18:37:32 dichy0318 python3[2333168]: 2026-09-02 18:37:32 INFO Response Time for GET to /redfish/v1/Systems/System.Embedded.1/Storage/CPU.1: 0.08768933638930321 seconds.
Sep 02 18:37:32 dichy0318 python3[2333168]: 2026-09-02 18:37:32 ERROR Exception occurred while using redfish object: 'StorageControllers'
Sep 02 18:37:32 dichy0318 python3[2333168]: Traceback (most recent call last):
Sep 02 18:37:32 dichy0318 python3[2333168]:   File "/var/lib/juju/agents/unit-hardware-observer-28/charm/venv/prometheus_hardware_exporter/collector.py", line 1036, in fetch
Sep 02 18:37:32 dichy0318 python3[2333168]:     ) = redfish_helper.get_storage_controller_data()
Sep 02 18:37:32 dichy0318 python3[2333168]:   File "/var/lib/juju/agents/unit-hardware-observer-28/charm/venv/prometheus_hardware_exporter/collectors/redfish.py", line 306, in get_storage_controller_data
Sep 02 18:37:32 dichy0318 python3[2333168]:     storage_controllers_list: List[Dict] = self.redfish_obj.get(curr_storage_uri).dict[
Sep 02 18:37:32 dichy0318 python3[2333168]: KeyError: 'StorageControllers'
Sep 02 18:37:32 dichy0318 python3[2333168]: 2026-09-02 18:37:32 INFO Attempt 1 of /redfish/v1/SessionService/Sessions/319876
Sep 02 18:37:32 dichy0318 python3[2333168]: 2026-09-02 18:37:32 INFO Response Time for DELETE to /redfish/v1/SessionService/Sessions/319876: 0.08308055624365807 seconds.

Reproduce / Test

N/A

Notes & References

No response

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The internal ticket has been created: https://warthogs.atlassian.net/browse/SOLENG-2256.

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