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 OpenSLO

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Introduction

The intent of this document is to outline the OpenSLO specification.

The goal of this project is to provide an open specification for defining and interfacing with SLOs to allow for a common approach, giving a set vendor-agnostic solution to defining and tracking SLOs. Platform specific implementation details are purposefully excluded from the scope of this specification.

Specification

Goals

  • Compliance with the Kubernetes YAML format.
  • Vendor-agnostic
  • Be flexible enough to be extended elsewhere

Object Types

💡 Note: Specific attributes are described in detail in the Notes and under each integration section.

General Schema

apiVersion: openslo/v1alpha
kind: SLO | Service
metadata:
  name: string
  displayName: string # optional
spec:
Notes
  • kind string - required, either SLO or Service
  • metadata.name: string - required field, convention for naming object from DNS RFC1123 name should:
    • contain at most 63 characters
    • contain only lowercase alphanumeric characters or -
    • start with an alphanumeric character
    • end with an alphanumeric character

SLO

A service level objective (SLO) is a target value or range of values for a service level that is described by a service level indicator (SLI).

apiVersion: openslo/v1alpha
kind: SLO
metadata:
  name: string
  displayName: string # optional
spec:
  description: string # optional
  service: [service name] # name of the service to associate this SLO with
  indicator: # represents the Service Level Indicator (SLI)
    thresholdMetric: # represents the metric used to inform the Service Level Object in the objectives stanza
      source: string # data source for the metric
      queryType: string # a name for the type of query to run on the data source
      query: string # the query to run to return the metric
  timeWindows:
    # exactly one item, one of possible rolling time window or calendar aligned
    # rolling time window
    - unit: Second
      count: numeric
      isRolling: true
    # or
    # calendar aligned time window
    - unit: Year | Quarter | Month | Week | Day
      count: numeric # count of time units for example count: 7 and unit: Day means 7 days window
      calendar:
        startTime: 2020-01-21 12:30:00 # date with time in 24h format, format without time zone
        timeZone: America/New_York # name as in IANA Time Zone Database
      isRolling: false # false or not defined
  budgetingMethod: Occurrences | Timeslices
  objectives: # see objectives below for details
Notes (SLO)
  • indicator optional, represents the Service Level Indicator (SLI). Currently this only supports one Metric, thresholdMetric, with ratioMetric supported in the objectives stanza.

  • indicator.thresholdMetric Metric, represents the query used for gathering data from metric sources. Raw data is used to compare objectives (threshold) values. If thresholdMetric is defined then ratioMetrics should be excluded in objectives.

  • timeWindows[ ] TimeWindow is a list but accepting only exactly one item, one of the rolling or calendar aligned time window:

    • Rolling time window. Minimum duration for rolling time window is 5 minutes, maximum 31 days).

      unit: Day | Hour | Minute
      count: numeric
      isRolling: true
    • Calendar Aligned time window. Minimum duration for calendar aligned time window is 1 day and maximum is 366 days.

      unit: Year | Quarter | Month | Week | Day
      count: numeric
      calendar:
          startTime: 2020-01-21 12:30:00 # date with time in 24h format
          timeZone: America/New_York # name as in IANA Time Zone Database
      # isRolling: false # for calendar aligned set false value or not set
  • description string optional field, contains at most 1050 characters

  • budgetingMethod enum(Occurrences | Timeslices), required field

    • Occurrences method uses a ratio of counts of good events and total count of the event.
    • Timeslices method uses a ratio of good time slices vs. total time slices in a budgeting period.
  • objectives[ ] Threshold, required field, described in Objectives section

Objectives

Objectives are the thresholds for your SLOs. You can use objectives to define the tolerance levels for your metrics

objectives:
  - displayName: string # optional
    op: lte | gte | lt | gt # conditional operator used to compare the SLI against the value. Only needed when using a thresholdMetric
    value: numeric # value used to compare metrics values. All objectives of the SLO need to have a unique value.
    target: numeric [0.0, 1.0) # budget target for given objective of the SLO
    timeSliceTarget: numeric (0.0, 1.0] # required only when budgetingMethod is set to TimeSlices
    # ratioMetric {good, total} should be defined only if thresholdMetric is not set.
    # ratioMetric good and total have to contain the same source type configuration (for example for prometheus).
    ratioMetric:
        incremental: true | false #todo: add description
        good: # the numerator
          source: string # data source for the "good" numerator
          queryType: string # a name for the type of query to run on the data source
          query: string # the query to run to return the numerator
        total: # the denominator
          source: string # data source for the "total" denominator
          queryType: string # a name for the type of query to run on the data source
          query: string # the query to run to return the denominator

Example:

objectives:
  - displayName: Foo Total Errors
    value:  1
    target: 0.98
    ratioMetrics:
        incremental: true
        good:
          source: datadog
          queryType: query
          query: sum:requests.error{*}
        total:
          source: datadog
          queryType: query
          query: sum:requests.total{*}
Notes (Objectives)
  • objectives[ ] Threshold, required field. If thresholdMetric has been defined, only one Threshold can be defined. However if using ratioMetric then any number of Thresholds can be defined.

  • op enum(lte | gte | lt | gt), operator used to compare the SLI against the value. Only needed when using thresholdMetric

  • value numeric, required field, used to compare values gathered from metric source

  • target numeric [0.0, 1.0), required, budget target for given objective of the SLO

  • targetTimeSlices numeric [0.0, 1.0], required only when budgeting method is set to TimeSlices

  • indicator.ratioMetric Metric {Good, Total}, if ratioMetric is defined then thresholdMetric should not be set in indicator

    • Good represents the query used for gathering data from metric sources used as the numerator. Received data is used to compare objectives (threshold) values to find good values.

    • Total represents the query used for gathering data from metric sources that is used as the denominator. Received data is used to compare objectives (threshold) values to find total number of metrics.


Service

A Service is a high-level grouping of SLO.

apiVersion: openslo/v1alpha
kind: Service
metadata:
  name: string
  displayName: string # optional
spec:
  description: string # optional up to 1050 characters

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