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transform SLO into SLI
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tobru committed Nov 10, 2023
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= Service Level Objectives
= Service Level Indicator (SLI)
:page-aliases: explanations/slos.adoc

APPUiO Managed OpenShift 4 comes with a collection of https://sre.google/sre-book/service-level-objectives/[service level objectives (SLOs)].
This document defines and explains these SLOs.
An APPUiO Managed cluster should meet these objectives to provide the expected service level to our customers.
APPUiO Managed OpenShift comes with a collection of https://sre.google/sre-book/service-level-objectives/[service level indicators (SLIs)].
This document defines and explains these SLIs.
All of the SLIs are in the scope of the https://products.vshn.ch/service_levels.html["Guaranteed Availability" Service Level].

We use the SLOs and https://sre.google/workbook/alerting-on-slos/#6-multiwindow-multi-burn-rate-alerts[Multiwindow, Mulit-Brun-Rate Alerts] as the basis of our on-call alerting.
We use the SLIs and https://sre.google/workbook/alerting-on-slos/#6-multiwindow-multi-burn-rate-alerts[Multiwindow, Mulit-Burn-Rate Alerts] as the basis of our on-call alerting.

IMPORTANT: These are internal service level *objectives*, not service level *agreements*.
We don't guarantee to meet these objectives at all times.

== Ingress

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=== Canary

****
*99.75% of all HTTP probes to a canary application succeed*
*HTTP probes to a canary application*
****

Probes are sent every minute from the ingress operator, inside the cluster, to the external address of the canary target.
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A misbehaving Kubernetes API directly impacts the service level.


=== Request Error Rate

****
*99.9% of all requests to the Kubernetes API server succeed or are invalid*
*Requests to the Kubernetes API server succeed or are invalid*
****

This is measured directly at the API server through the following metrics.
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=== Uptime

****
*99.9% of all HTTP probes to the Kubernetes API server succeed*
*HTTP probes to the Kubernetes API server succeed*
****

Probes are sent every 10 seconds from a blackbox exporter inside the cluster to the readiness endpoint of the Kubernetes API server.
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=== Canary

****
*99.75% of canary pods start successfully*
*Canary pods start successfully*
****

A controller starts a known good canary pod every minute and checks if it successfully started after 3 minutes.
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=== CSI Operations

****
*99.5% of all CSI operations complete successfully*
*CSI operations complete successfully*
****

CSI operations are any interactions of the kubelet or controller-manager with the CSI provider.
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=== Packet Loss

****
*99.5% of all ICMP pings between canary pods succeed*
*ICMP pings between canary pods succeed*
****

A network canary daemonset starts a canary pod on every node.
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* Monitoring
** xref:oc4:ROOT:explanations/cluster_monitoring.adoc[]
** xref:oc4:ROOT:explanations/slos.adoc[]
** xref:oc4:ROOT:explanations/slis.adoc[]
** xref:oc4:ROOT:how-tos/monitoring/global-monitoring.adoc[]
** xref:oc4:ROOT:how-tos/monitoring/handle_alerts.adoc[]
** xref:oc4:ROOT:how-tos/monitoring/remove_rules.adoc[]
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