https://github.com/OpenSLO/OpenSLO

Open specification for defining and expressing service level objectives (SLO)
https://github.com/OpenSLO/OpenSLO

slo spec specification

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Open specification for defining and expressing service level objectives (SLO)

• Host: GitHub
• URL: https://github.com/OpenSLO/OpenSLO
• Owner: OpenSLO
• License: apache-2.0
• Created: 2021-04-27T23:34:53.000Z (about 3 years ago)
• Default Branch: main
• Last Pushed: 2024-06-04T09:41:31.000Z (24 days ago)
• Last Synced: 2024-06-04T11:00:37.324Z (24 days ago)
• Topics: slo, spec, specification
• Language: Go
• Homepage: https://www.openslo.com
• Size: 938 KB
• Stars: 1,306
• Watchers: 35
• Forks: 61
• Open Issues: 22
• Metadata Files:
  • Readme: README.md
  • Contributing: CONTRIBUTING.md
  • License: LICENSE
  • Code of conduct: CODE_OF_CONDUCT.md

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• awesome-stars - OpenSLO
• awesome-github-repos - OpenSLO/OpenSLO - Open specification for defining and expressing service level objectives (SLO) (Go)
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README

        
#

  

  

## Table of Contents

- [Introduction](#introduction)

- [Specification](#specification)

  - [Goals](#goals)

  - [General Schema](#general-schema)

    - [Notes (General Schema)](#notes-general-schema)

  - [Custom Data Types](#custom-data-types)

    - [duration-shorthand](#duration-shorthand)

  - [Object Types](#object-types)

    - [DataSource](#datasource)

      - [Notes (DataSource)](#notes-datasource)

    - [SLO](#slo)

      - [Notes (SLO)](#notes-slo)

      - [Objectives](#objectives)

        - [Notes (Objectives)](#notes-objectives)

    - [SLI](#sli)

      - [Notes (SLI)](#notes-sli)

      - [Ratio Metric](#ratio-metric)

    - [AlertPolicy](#alertpolicy)

      - [Notes (AlertPolicy)](#notes-alertpolicy)

    - [AlertCondition](#alertcondition)

      - [Notes (AlertCondition)](#notes-alertcondition)

    - [AlertNotificationTarget](#alertnotificationtarget)

      - [Notes (AlertNotificationTarget)](#notes-alertnotificationtarget)

    - [Service](#service)

- [Examples](examples/README.md)

- [Glossary](glossary/README.md)

- Work in progress for future versions

  - [v2alpha1](enhancements/v2alpha1.md)

## 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 SLOs

to enable a common, vendor–agnostic approach to tracking and interfacing with

SLOs. Platform-specific implementation details are purposefully excluded from

the scope of this specification.

OpenSLO is an open specification i.e., it is a specification created and

controlled, in an open and fair process, by an association or a standardization

body intending to achieve interoperability and interchangeability. An open

specification is not controlled by a single company or individual or by a group

with discriminatory membership criteria. Additionally, this specification is

designed to be extended where needed to meet the needs of the implementation.

Before making a contribute please read our [contribution guideline](https://github.com/OpenSLO/OpenSLO/blob/main/CONTRIBUTING.md).

## Specification

### Goals

- Compliance with the Kubernetes YAML format

- Vendor-agnostic

- Be flexible enough to be extended elsewhere

### General Schema

```yaml

apiVersion: openslo/v1

kind: DataSource | SLO | SLI | AlertPolicy | AlertCondition | AlertNotificationTarget | Service

metadata:

  name: string

  displayName: string # optional

  labels: # optional, it's allowed to assign multiple values to a single key

    # example labels

    organization: "acme"

    team:

      - "identity"

      - "rbac"

    costCentre: "project1"

    serviceTier:

      - "tier-1"

  annotations: # optional

    # example annotations

    openslo.com/key1: value1

    fooimplementation.com/key2: value2

spec:

```

#### Notes (General Schema)

- **kind** *string* - required, one of: [DataSource](#datasource), [SLO](#slo),

  [SLI](#sli), [AlertPolicy](#alertpolicy), [AlertCondition](#alertcondition),

  [AlertNotificationTarget](#alertnotificationtarget), [Service](#service)

- **metadata.name:** *string* - required field

  - all implementations must at least support object names that follow [RFC1123][rfc1123-names]:

    - are up to 63 characters in length

    - contain lowercase alphanumeric characters or `-`

    - start with an alphanumeric character

    - end with an alphanumeric character

  - implementations are additionally encouraged to support names that:

    - are up to 255 characters in length

    - contain lowercase alphanumeric characters or `-`, `.`, `|`, `/`, `\`

- **metadata.labels:** *map[string]string|string[]* - optional field `key` <> `value`

  - the `key` segment is required and must contain at most 63 characters beginning and ending

     with an alphanumeric character `[a-z0-9A-Z]` with dashes `-`, underscores `_`, dots `.`

     and alphanumerics between.

  - the `value` of `key` segment can be a string or an array of strings

- **metadata.annotations:** *map[string]string* - optional field `key` <> `value`

  - `annotations` should be used to define implementation / system specific metadata about the SLO.

    For example, it can be metadata about a dashboard url, or how to name a metric created by the SLI, etc.

  - `key` have two segments: an optional `prefix` and `name`, separated by a slash `/`

  - the `name` segment is required and must contain at most 63 characters beginning and ending

    with an alphanumeric character `[a-z0-9A-Z]` with dashes `-`, underscores `_`, dots `.`

    and alphanumerics between.

  - the `prefix` is optional and must be a DNS subdomain: a series of DNS labels separated by dots `.`,

    it must contain at most 253 characters, followed by a slash `/`.

  - the `openslo.com/` is reserved for OpenSLO usage

### Custom Data Types

#### duration-shorthand

The duration shorthand is specified as a single–word string (no whitespaces) consisting

of a positive integer `number` followed by a case–sensitive single–character `postfix`.

Allowed postfixes are:

- *m* – minutes

- *h* – hours

- *d* – days

- *w* – weeks

- *M* – months

- *Q* – quarters

- *Y* – years

Examples: `12h`, `4w`, `1M`, `1Q`, `365d`, `1Y`.

This specification does not put requirements on how (or whether) to implement each

postfix, therefore implementers are free to pick an implementation that best suits

their environments.

There is however the possibility that future versions of this spec will take a more

prescriptive stance on this issue.

### Object Types

> 💡 **Note:** Specific attributes are described in detail in the **Notes**

> subsection of each object type's section.

#### DataSource

A DataSource represents connection details with a particular metric source.

> [Check work in progress for v2.](enhancements/v2alpha1.md#datasource)

```yaml

apiVersion: openslo/v1

kind: DataSource

metadata:

  name: string

  displayName: string # optional

spec:

  description: string # optional up to 1050 characters

  type: string # predefined type e.g. Prometheus, Datadog, etc.

  connectionDetails:

    # fields used for creating a connection with particular datasource e.g. AccessKeys, SecretKeys, etc.

    # everything that is valid YAML can be put here

```

##### Notes (DataSource)

DataSource enables reusing one source between many SLOs and moving

connection specific details (e.g. authentication) away from SLO definitions.

This spec does not enforce naming conventions for data source types, however

the OpenSLO project will publish guidelines in the form of supplementary materials

once common patterns start emerging from implementations.

An example of the DataSource kind can be:

```yaml

apiVersion: openslo/v1

kind: DataSource

metadata:

  name: string

  displayName: string # optional

spec:

  type: CloudWatch

  connectionDetails:

    accessKeyID: accessKey

    secretAccessKey: secretAccessKey

```

---

#### SLO

A service level objective (SLO) is a target value or a range of values for

a service level that is described by a service level indicator (SLI).

> [Check work in progress for v2.](enhancements/v2alpha1.md#slo)

```yaml

apiVersion: openslo/v1

kind: SLO

metadata:

  name: string

  displayName: string # optional

spec:

  description: string # optional up to 1050 characters

  service: string # name of the service to associate this SLO with, may refer (depends on implementation) to existing object Kind: Service

  indicator: # see SLI below for details

  indicatorRef: string # name of the SLI. Required if indicator is not given.

  timeWindow:

    # exactly one item; one of possible: rolling or calendar–aligned time window

    ## rolling time window

    - duration: duration-shorthand # duration of the window eg 1d, 4w

      isRolling: true

    # or

    ## calendar–aligned time window

    - duration: duration-shorthand # duration of the window eg 1M, 1Q, 1Y

      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 # if omitted assumed `false` if `calendar:` is present

  budgetingMethod: Occurrences | Timeslices | RatioTimeslices

  objectives: # see objectives below for details

  alertPolicies: # see alert policies below for details

```

##### Notes (SLO)

- **indicator** optional, represents the Service Level Indicator (SLI),

  described in [SLI](#sli) section.

  One of `indicator` or `indicatorRef` must be given. If declaring composite SLO must be moved into `objectives[]`.

- **indicatorRef** optional, this is the name of Service Level Indicator (SLI).

  One of `indicator` or `indicatorRef` must be given. If declaring composite SLO must be moved into `objectives[]`.

- **timeWindow[ ]** optional, *TimeWindow* is a list but accepting only exactly one

  item, one of the rolling or calendar aligned time window:

  - Rolling time window. Duration should be provided in shorthand format

    e.g. 5m, 4w, 31d.

  - Calendar Aligned time window. Duration should be provided in shorthand format

    eg. 1d, 2M, 1Q, 366d.

- **description** *string* optional field, contains at most 1050 characters

- **budgetingMethod** *enum(Occurrences \| Timeslices \| RatioTimeslices)*, required field

  - Occurrences method uses a ratio of counts of good events to the total count of the events.

  - Timeslices method uses a ratio of good time slices to total time slices in a budgeting period.

  - RatioTimeslices method uses an average of all time slices' success ratios in a budgeting period.

- **objectives[ ]** *Threshold*, required field, described in [Objectives](#objectives)

  section. If `thresholdMetric` has been defined, only one Threshold can be defined.

  However, if using `ratioMetric` then any number of Thresholds can be defined.

- **alertPolicies\[ \]** *AlertPolicy*, optional field.

  section. An alert policy can be defined inline or can refer to an [Alert Policies](#alertpolicy) object,

  in which case the following are required:

  - **alertPolicyRef** *string*: this is the name or path to the AlertPolicy

##### Objectives

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

the tolerance levels for your metrics.

```yaml

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 # optional, value used to compare threshold metrics. Only needed when using a thresholdMetric

    target: numeric [0.0, 1.0) # budget target for given objective of the SLO, can't be used with targetPercent

    targetPercent: numeric [0.0, 100) # budget target for given objective of the SLO, can't be used with target

    timeSliceTarget: numeric (0.0, 1.0] # required only when budgetingMethod is set to TimeSlices

    timeSliceWindow: number | duration-shorthand # required only when budgetingMethod is set to TimeSlices or RatioTimeslices

    indicator: # required only when creating composite SLO, see SLI below for more details

    indicatorRef: string # required only when creating composite SLO, required if indicator is not given.

    compositeWeight: numeric (0.0, inf+] # optional, supported only when declaring multiple objectives, default value 1.

```

Example:

```yaml

objectives:

  - displayName: Foo Total Errors

    target: 0.98

  - displayName: Bar Total Errors

    targetPercent: 99.99

```

###### Notes (Objectives)

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

- **value** *numeric*, required field, used to compare values gathered from

  metric source. Only needed when using a `thresholdMetric`.

Either `target` or `targetPercent` must be used.

- **target** *numeric [0.0, 1.0)*, optional, but either this or `targetPercent` must

  be used. Budget target for a given objective of the SLO. A `target: 0.9995` is

  equivalent to `targetPercent: 99.95`.

- **targetPercent**: *numeric [0.0, 100)*, optional, but either this or `target` must

  be used. Budget target for a given objective of the SLO. A `targetPercent: 99.95`

  is equivalent to `target: 0.9995`.

- **timeSliceTarget** *numeric [0.0, 1.0]*, required only when budgeting

  method is set to TimeSlices

- **timeSliceWindow** *(numeric | duration-shorthand)*, required only when budgeting

  method is set to TimeSlices or RatioTimeslices. Denotes the size of a time slice for

  which data will be evaluated e.g. 5, 1m, 10m, 2h, 1d. Also ascertains the frequency

  at which to run the queries. Default interpretation of unit if specified as a number

  in minutes.

- **indicator** optional, represents the Service Level Indicator (SLI),

  described in [SLI](#sli) section.

  One of `indicator` or `indicatorRef` must be given in objective when creating composite SLO.

- **indicatorRef** optional, this is the name of Service Level Indicator (SLI).

  One of `indicator` or `indicatorRef` must be given when creating composite SLO.

##### Notes (Composite SLO)

**Composite SLO** goal of composite SLO is to enable user an end-to-end journey, it is done by defining many

  independent objectives. Each objective can have different queries, data sources and targets. The basic implementation

  assumes that the Composite Error Budget burns if the Error Budget for any of the SLO objectives within the Composite SLO

  is burning. The logic of those calculations is the same for Composite SLOs as for regular (standard) objectives and SLOs.

**Weight** allows the user to change the impact of a given SLO on the whole composite SLO. Weight is just multiplier, it

  means that if weight is `0.5`, SLO will have half impact as default, on the other hand if weight is `100`, this SLO will

  be 100 times more impactful. By default, weight has value 1 and doesn't need to be specified.

**Calculations** should be as simple as possible to make composite SLO intuitive and easy to implement. It is hard to compare

different error budget calculating methods therefore all composite objectives need to be calculated with one type of error

budget calculating method. Here is brief description how given budgeting method should impact composite SLO and how wight scale its

impact:

- Occurrences - if SLO burns its budget composite is burning its budget at the same rate. Each violation that consumed

  SLO's budget will impact Composite at the same rate. Weight multiplies the rate of burning of SLO (referenced as burn

  rate) that burns composite.

- Timeslices - this is binary depending on whether it was a good or bad minute. If it was a bad minute for any individual

  objective, it's considered a bad minute for the Composite SLO.

- Ratiotimeslices - it is the sum of missing up to 100 percent. If two SLOs have average of Ratiotimeslices on 95%,

  composite will have average of Ratiotimeslices on 90%. Weight multiplies missing part of given slo.

#### SLI

A service level indicator (SLI) represents how to read metrics from data sources.

> [Check work in progress for v2.](enhancements/v2alpha1.md#sli)

```yaml

apiVersion: openslo/v1

kind: SLI

metadata:

  name: string

  displayName: string # optional

spec:

  description: string # optional up to 1050 characters

  thresholdMetric: # either thresholdMetric or ratioMetric must be provided

    metricSource:

      metricSourceRef: string # optional, this field can be used to refer to DataSource object

      type: string # optional, this field describes predefined metric source type e.g. Prometheus, Datadog, etc.

      spec:

        # arbitrary chosen fields for every data source type to make it comfortable to use

        # anything that is valid YAML can be put here.

  ratioMetric: # either thresholdMetric or ratioMetric must be provided

    counter: true | false # true if the metric is a monotonically increasing counter,

                          # or false, if it is a single number that can arbitrarily go up or down

                          # ignored when using "raw"

    good: # the numerator, either "good" or "bad" must be provided if "total" is used

      metricSource:

        metricSourceRef: string # optional

        type: string # optional

        spec:

          # arbitrary chosen fields for every data source type to make it comfortable to use.

    bad: # the numerator, either "good" or "bad" must be provided if "total" is used

      metricSource:

        metricSourceRef: string # optional

        type: string # optional

        spec:

          # arbitrary chosen fields for every data source type to make it comfortable to use.

    total: # the denominator used with either "good" or "bad", either this or "raw" must be used

      metricSource:

        metricSourceRef: string # optional

        type: string # optional

        spec:

          # arbitrary chosen fields for every data source type to make it comfortable to use.

    rawType: success | failure # required with "raw", indicates how the stored ratio was calculated:

                               #  success – good/total

                               #  failure – bad/total

    raw: # the precomputed ratio stored as a metric, can't be used together with good/bad/total

      metricSource:

        metricSourceRef: string # optional

        type: string # optional

        spec:

          # arbitrary chosen fields for every data source type to make it comfortable to use.

```

##### Notes (SLI)

- **description** *string* optional field, contains at most 1050 characters

Either `ratioMetric` or `thresholdMetric` must be used.

- **thresholdMetric** *Metric*, represents the query used for

  gathering data from metric sources. Raw data is used to compare objectives

  (threshold) values.

- **ratioMetric** *Metric {good, total}, {bad, total} or raw*.

  - **counter** *enum(true \| false)*, specifies whether the metric is a monotonically

   increasing counter. Has no effect when using a `raw` query.

  - **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. If `bad` is defined then `good` must not be set.

  - **bad** 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 bad values. If `good` is defined then `bad` must not be set.

  - **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.

  - **rawType** *enum(success \| failure)*, required when using `raw`, specifies

   whether the ratios represented by the "raw" ratio metric are of successes or failures.

   Not to be used with `good` and `bad` as picking one of those determines the type of

   ratio.

  - **raw** represents the query used for gathering already precomputed ratios.

   The type of ratio (*success* or *failure*) is specified using `rawType`.

An example of an SLO where SLI is inlined:

```yaml

apiVersion: openslo/v1

kind: SLO

metadata:

  name: foo-slo

  displayName: Foo SLO

spec:

  service: foo

  indicator:

    metadata:

      name: foo-error

      displayName: Foo Error

    spec:

      ratioMetric:

        counter: true

        good:

          metricSource:

            metricSourceRef: datadog-datasource

            type: Datadog

            spec:

              query: sum:trace.http.request.hits.by_http_status{http.status_code:200}.as_count()

        total:

          metricSource:

            metricSourceRef: datadog-datasource

            type: Datadog

            spec:

              query: sum:trace.http.request.hits.by_http_status{*}.as_count()

  objectives:

    - displayName: Foo Total Errors

      target: 0.98

```

##### Ratio Metric

If a service level indicator has `ratioMetric` defined, the following maths can

be used to calculate the value of the SLI. Below we describe the advised formulas

for calculating the indicator value.

*Good-Total queries*

If the `good` and `total` queries are given then following formula can be used

to calculate the value:

```text

indicatorValue = good / total

```

If we have 99 good requests out of a total of 100 requests, the calculated value

for the indicator would be: `99 / 100  = 0.99`. This represents 99% on a 0-100 scale

using the formula `0.99 * 100 = 99`.

*Bad-Total queries*

If the `bad` and `total` queries are given then following formula can be used

to calculate the value:

```text

indicatorValue = ( total - bad ) / total

```

If we have 1 error out of a total of 100 requests, the calculated value for

the indicator would be: `(100 - 1) = 0.99`. This represents 99% on a 0-100 scale

using the formula `0.99 * 100 = 99`.

> 💡 **Note:** As you can see for both query combinations we end up with the same calculated

> value for the service level indicator.

The required `spec` key will be used to pass extraneous data to the data source. The goal of this approach

is to provide maximum flexibility when querying data from a particular source. In the following examples

we can see that this works fine for both simple and more complex cases.

An example of **ratioMetric**:

```yaml

ratioMetric:

  counter: true

  good:

    metricSource:

      type: Prometheus

      metricSourceRef: prometheus-datasource

      spec:

        query: sum(localhost_server_requests{code=~"2xx|3xx",host="*",instance="127.0.0.1:9090"})

  total:

    metricSource:

      type: Prometheus

      metricSourceRef: prometheus-datasource

      spec:

        query: localhost_server_requests{code="total",host="*",instance="127.0.0.1:9090"}

```

An example of **thresholdMetric**:

```yaml

thresholdMetric:

  metricSource:

    metricSourceRef: redshift-datasource

    spec:

      region: eu-central-1

      clusterId: metrics-cluster

      databaseName: metrics-db

      query: SELECT value, timestamp FROM metrics WHERE timestamp BETWEEN :date_from AND :date_to

```

Field `type` can be omitted because the type will be inferred from the DataSource when `metricSourceRef` is specified.

An example **thresholdMetric** that does not reference a defined DataSource:

```yaml

thresholdMetric:

  metricSource:

    type: Redshift

    spec:

      region: eu-central-1

      clusterId: metrics-cluster

      databaseName: metrics-db

      query: SELECT value, timestamp FROM metrics WHERE timestamp BETWEEN :date_from AND :date_to

      accessKeyID: accessKey

      secretAccessKey: secretAccessKey

 ```

 Field `type` can't be omitted because the reference to an existing DataSource is not specified.

---

#### AlertPolicy

An Alert Policy allows you to define the alert conditions for an SLO.

```yaml

apiVersion: openslo/v1

kind: AlertPolicy

metadata:

  name: string

  displayName: string # optional

spec:

  description: string # optional up to 1050 characters

  alertWhenNoData: boolean

  alertWhenResolved: boolean

  alertWhenBreaching: boolean

  conditions: # list of alert conditions

    - conditionRef: # required when alert condition is not inlined

  notificationTargets:

  - targetRef: # required when alert notification target is not inlined

```

##### Notes (AlertPolicy)

- **description** *string*, optional description about the alert policy, contains at most 1050 characters

- **alertWhenBreaching** *boolean*, `true`, `false`, whether the alert should be triggered

  when the condition is breaching

- **alertWhenResolved** *boolean*, `true`, `false`, whether the alert should be triggered

  when the condition is resolved

- **alertWhenNoData** *boolean*, `true`, `false`, whether the alert should be triggered

  when the condition indicates that no data is available

- **conditions\[ \]** *Alert Condition*, an array, (max of one condition), required field.

  A condition can be defined inline or can refer to external Alert condition defined in this case the following are required:

  - **conditionRef** *string*: this is the name or path the Alert condition

- **notificationTargets\[ \]** *Alert Notification Target*, required field.

  A condition can be defined inline or can refer to an [AlertNotificationTarget](#alertnotificationtarget)

  object, in which case the following are required:

  - **targetRef** *string*: this is the name or path to the AlertNotificationTarget

> 💡 **Note:** The `conditions` field is of the type `array` of *AlertCondition*

> but only allows one single condition to be defined.

> The use of an array is for future-proofing purposes.

An example of an Alert policy which refers to another Alert Condition:

```yaml

apiVersion: openslo/v1

kind: AlertPolicy

metadata:

  name: AlertPolicy

  displayName: Alert Policy

spec:

  description: Alert policy for cpu usage breaches, notifies on-call devops via email

  alertWhenBreaching: true

  alertWhenResolved: false

  conditions:

    - conditionRef: cpu-usage-breach

  notificationTargets:

    - targetRef: OnCallDevopsMailNotification

```

An example of an Alert Policy were the Alert Condition is inlined:

```yaml

apiVersion: openslo/v1

kind: AlertPolicy

metadata:

  name: AlertPolicy

  displayName: Alert Policy

spec:

  description: Alert policy for cpu usage breaches, notifies on-call devops via email

  alertWhenBreaching: true

  alertWhenResolved: false

  conditions:

    - kind: AlertCondition

      metadata:

        name: cpu-usage-breach

        displayName: CPU Usage breaching

      spec:

        description: SLO burn rate for cpu-usage-breach exceeds 2

        severity: page

        condition:

          kind: burnrate

          op: lte

          threshold: 2

          lookbackWindow: 1h

          alertAfter: 5m

  notificationTargets:

    - targetRef: OnCallDevopsMailNotification

```

---

#### AlertCondition

An Alert Condition allows you to define under which conditions an alert for an SLO

needs to be triggered.

```yaml

apiVersion: openslo/v1

kind: AlertCondition

metadata:

  name: string

  displayName: string # optional

spec:

  description: string # optional up to 1050 characters

  severity: string # required

  condition: # required

    kind: string

    op: enum

    threshold: number

    lookbackWindow: duration-shorthand

    alertAfter: duration-shorthand

```

##### Notes (AlertCondition)

- **description** *string*, optional description about the alert condition, contains at most 1050 characters

- **severity** *string*, required field describing the severity level of the alert (ex. "sev1", "page", etc.)

- **condition**, required field. Defines the conditions of the alert

  - **kind** *enum(burnrate)* the kind of alerting condition thats checked, defaults to `burnrate`

If the kind is `burnrate` the following fields are required:

- **op** *enum(lte | gte | lt | gt)*, required field, the conditional operator used to compare against the threshold

- **threshold** *number*, required field, the threshold that you want alert on

- **lookbackWindow** *duration-shorthand*, required field, the time-frame for which to calculate the threshold e.g. `5m`

- **alertAfter** *duration-shorthand*: required field, the duration the condition needs to be valid for before alerting, defaults to `0m`

If the alert condition is breaching, and the alert policy has `alertWhenBreaching` set to `true`

the alert will be triggered

If the alert condition is resolved, and the alert policy has `alertWhenResolved` set to `true`

the alert will be triggered

If the *service level objective* associated with the alert condition returns

no value for the burn rate, for example, due to the service level indicators

missing data (e.g. no time series being returned) and the `alertWhenNoData`

is set  to `true` the alert will be triggered.

> 💡 **Note:** The `alertWhenBreaching` and `alertWhenResolved`, `alertWhenNoData` can be combined,

> if you want an alert to trigger whenever at least one of these conditions is true.

---

An example of an alert condition:

```yaml

apiVersion: openslo/v1

kind: AlertCondition

metadata:

  name: cpu-usage-breach

  displayName: CPU usage breach

spec:

  description: If the CPU usage is too high for given period then it should alert

  severity: page

  condition:

    kind: burnrate

    op: lte

    threshold: 2

    lookbackWindow: 1h

    alertAfter: 5m

```

---

#### AlertNotificationTarget

An Alert Notification Target defines the possible targets where alert notifications

should be delivered to. For example, this can be a web-hook, Slack or any other

custom target.

```yaml

apiVersion: openslo/v1

kind: AlertNotificationTarget

metadata:

  name: string

  displayName: string # optional, human readable name

spec:

  target: # required

  description: # optional

```

An example Alert Notification Target:

```yaml

apiVersion: openslo/v1

kind: AlertNotificationTarget

metadata:

  name: OnCallDevopsMailNotification

spec:

  description: Notifies by a mail message to the on-call devops mailing group

  target: email

```

Alternatively, a similar notification target can be defined for Slack like this:

```yaml

apiVersion: openslo/v1

kind: AlertNotificationTarget

metadata:

  name: OnCallDevopsSlackNotification

spec:

  description: "Sends P1 alert notifications to the slack channel"

  target: slack

```

##### Notes (AlertNotificationTarget)

- **target** *string*, describes the target of the notification, e.g. Slack, email, web-hook, Opsgenie etc

- **description** *string*, optional description about the notification target, contains at most 1050 characters

> 💡 **Note:** The way the alert notification targets are is an implementation detail of the

> system that consumes the OpenSLO specification.

>

> For example, if the OpenSLO is consumed by a solution that generates Prometheus recording rules,

> and alerts, you can imagine that the name of the alert notification gets passed as a label

> to Alertmanager which then can be routed accordingly based on this label.

---

#### Service

A Service is a high-level grouping of SLO. It may be defined before creating SLO to be able to refer to it in SLO's `spec.service`.

Multiple SLOs can refer to the same Service.

```yaml

apiVersion: openslo/v1

kind: Service

metadata:

  name: string

  displayName: string # optional

spec:

  description: string # optional up to 1050 characters

```

[rfc1123-names]: https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#dns-label-names