version: 1
id: slo-definition-basics
title: Define an Availability SLO
summary: Turn success/total request counts into an SLI ratio, pick a 99.9% SLO target, and document a 30-day measurement window for payments-api.
difficulty: intermediate
estimatedMinutes: 30
prerequisites: [observability-metrics-alerts]
image: alpine:3.21
shell: /bin/sh
setup:
  - "apk add --no-cache bc >/dev/null"
  - "mkdir -p /workspace/slo /workspace/docs"
  - "printf 'http_requests_total{status=\"200\"} 9970\\nhttp_requests_total{status=\"500\"} 30\\n' > /workspace/slo/api.prom"
  - "printf 'Ticket: payments-api needs an availability SLO.\\nCompute SLI from success/total, target 99.9%, window 30d.\\n' > /workspace/slo/TICKET.md"
tasks:
  - id: compute-sli
    title: Compute the availability SLI
    description: 'From /workspace/slo/api.prom, treat status 200 as success and all samples as total. Write the success count to /workspace/slo/success.txt, total to /workspace/slo/total.txt, and the SLI percent with one decimal place to /workspace/slo/sli.txt (9970/10000*100 = 99.7).'
    hints:
      - 'Tip code SLI_RATIO: availability SLI = successful requests / total requests.'
      - 'Success is the 200 counter (9970); total is 9970+30=10000.'
      - 'sli.txt should contain 99.7'
    checks:
      - type: file
        name: Success count recorded
        path: /workspace/slo/success.txt
        value: "9970"
      - type: file
        name: Total count recorded
        path: /workspace/slo/total.txt
        value: "10000"
      - type: file
        name: SLI percent recorded
        path: /workspace/slo/sli.txt
        value: "99.7"
  - id: define-slo
    title: Author the SLO brief
    description: 'Create /workspace/docs/SLO.md with headings SLI, Target, and Window. SLI must mention success or availability. Target must include 99.9. Window must mention 30. Write /workspace/slo/STATUS.txt containing SLO_OK.'
    hints:
      - 'Tip code SLO_TARGET: pick an explicit target like 99.9% availability.'
      - 'Tip code WINDOW_30D: state the measurement window (30 days) so budget math is comparable.'
      - 'STATUS.txt should include SLO_OK.'
    checks:
      - type: file
        name: SLI section present
        path: /workspace/docs/SLO.md
        value: SLI
      - type: file
        name: Target section present
        path: /workspace/docs/SLO.md
        value: Target
      - type: file
        name: Window section present
        path: /workspace/docs/SLO.md
        value: Window
      - type: command
        name: SLI mentions availability
        command: "grep -A3 '^#* *SLI' /workspace/docs/SLO.md | grep -Eqi 'success|availability'"
      - type: command
        name: Target is 99.9
        command: "grep -A3 '^#* *Target' /workspace/docs/SLO.md | grep -Fq '99.9'"
      - type: command
        name: Window is 30 days
        command: "grep -A3 '^#* *Window' /workspace/docs/SLO.md | grep -Eqi '30'"
      - type: file
        name: SLO status ok
        path: /workspace/slo/STATUS.txt
        value: SLO_OK
limits: {cpus: "0.5", memory: 128m, pids: 64, timeout: 1800, network: false}