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SLOs_validation.md

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SLOs validation

Pass/fail based on metrics captured from the cluster is important in addition to checking the health status and recovery. Kraken supports:

Checking for critical alerts post chaos

If enabled, the check runs at the end of each scenario ( post chaos ) and Kraken exits in case critical alerts are firing to allow user to debug. You can enable it in the config:

performance_monitoring:
    check_critical_alerts: False                          # When enabled will check prometheus for critical alerts firing post chaos

Validation and alerting based on the queries defined by the user during chaos

Takes PromQL queries as input and modifies the return code of the run to determine pass/fail. It's especially useful in case of automated runs in CI where user won't be able to monitor the system. This feature can be enabled in the config by setting the following:

performance_monitoring:
    prometheus_url:                                       # The prometheus url/route is automatically obtained in case of OpenShift, please set it when the distribution is Kubernetes.
    prometheus_bearer_token:                              # The bearer token is automatically obtained in case of OpenShift, please set it when the distribution is Kubernetes. This is needed to authenticate with prometheus.
    enable_alerts: True                                   # Runs the queries specified in the alert profile and displays the info or exits 1 when severity=error.
    alert_profile: config/alerts.yaml                          # Path to alert profile with the prometheus queries.

Alert profile

A couple of alert profiles alerts are shipped by default and can be tweaked to add more queries to alert on. User can provide a URL or path to the file in the config. The following are a few alerts examples:

- expr: avg_over_time(histogram_quantile(0.99, rate(etcd_disk_wal_fsync_duration_seconds_bucket[2m]))[5m:]) > 0.01
  description: 5 minutes avg. etcd fsync latency on {{$labels.pod}} higher than 10ms {{$value}}
  severity: error

- expr: avg_over_time(histogram_quantile(0.99, rate(etcd_network_peer_round_trip_time_seconds_bucket[5m]))[5m:]) > 0.1
  description: 5 minutes avg. etcd network peer round trip on {{$labels.pod}} higher than 100ms {{$value}}
  severity: info

- expr: increase(etcd_server_leader_changes_seen_total[2m]) > 0
  description: etcd leader changes observed
  severity: critical

Kube-burner supports setting the severity for the alerts with each one having different effects:

info: Prints an info message with the alarm description to stdout. By default all expressions have this severity.
warning: Prints a warning message with the alarm description to stdout.
error: Prints a error message with the alarm description to stdout and makes kube-burner rc = 1
critical: Prints a fatal message with the alarm description to stdout and exits execution inmediatly with rc != 0