The Redfish® telemetry service

As per the DMTF Redfish telemetry whitepaper, the standard telemetry service allows clients to:

  • Obtain the characteristics and details of a metric (metadata).
  • Specify metric reports that periodically report a set of metrics (aggregation).
  • Specify trigger thresholds against a metric that is monitored (monitoring).
NOTE

As this service is dependent of the computer chipset (Intel, AMD, ARM...) it may not be present in all types of servers.

When implemented, the telemetry entry point URI is /redfish/v1/TelemetryService.

Metric reports can be stored locally, sent remotely or both.

Subscribing for metric reports

Metric reports can be sent remotely toward an event listener after an event subscription with EventFormatType=MetricReport. The following example shows a metric report subscription toward an HPE iLO 6.

Generic subscription requestBody request
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POST /redfish/v1/EventService/Subscriptions/
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{
    "Destination": "https://myeventreciever/eventreceiver",
    "EventFormatType": "MetricReport",
    "MetricReportDefinitions": [
        "/redfish/v1/TelemetryService/MetricReportDefinitions/CPUUtil",
        "/redfish/v1/TelemetryService/MetricReportDefinitions/CPU0Power",
        "/redfish/v1/TelemetryService/MetricReportDefinitions/CPU1Power"
    ],
    "HttpHeaders": {
        "Header1": "HeaderValue1"
    },
    "Context": "context string",
    "Oem": {
        "Hpe": {
            "DeliveryRetryIntervalInSeconds": 30,
            "RequestedMaxEventsToQueue": 20,
            "DeliveryRetryAttempts": 5,
            "RetireOldEventInMinutes": 10
        }
    }
}

Subscribed metric reports can be sent to the event listener periodically only when MetricReportDefinitionType property of the metric report definition URI is set to Periodic. In the cases of OnRequest or OnChange streaming will be stopped. This is defined in the MetricReportDefinitionType property of the metric report definition URI for each metric report that is eligible to subscription.

The following example sets the frequency of the CPUUtil metric report of an HPE iLO 6 to 1 day (P1DT), starting on a specific day and GMT time.

Generic requestBody request
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PATCH /redfish/v1/TelemetryService/MetricReportDefinitions/CPUUtil/
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{
    "MetricReportDefinitionType": "Periodic",
    "Schedule": {
    "RecurrenceInterval": "P1DT",
    "InitialStartTime": "2023-06-01T01:00:00Z"
    }
}

Refer to this documentation section for examples and detail concerning the implementation of the Redfish® Telemetry service in HPE iLO 5 and iLO 6.