workspace

/opt/lab-classroom/class62/

mutation_scope

Every file created or modified by this lab is beneath /opt/lab-classroom/class62/.

steps

step

1

title

Create the isolated class workspace

command

mkdir -p /opt/lab-classroom/class62 && cd /opt/lab-classroom/class62 && pwd

explanation

The printed working directory must be /opt/lab-classroom/class62. Stop if the account cannot create or write this directory.

step

2

title

Create the synthetic exporter

command

cat > /opt/lab-classroom/class62/exporter.py <<'PY'

!/usr/bin/env python3

import json
import sys

SERVICES = ("sonarr", "radarr")
STATE_NUMBER = {"critical": 0, "warning": 1, "healthy": 2}

def validate_record(service, record):
if not isinstance(record, dict):
raise ValueError(f"{service}: record must be an object")
reachable = record.get("reachable")
if not isinstance(reachable, bool):
raise ValueError(f"{service}: reachable must be a Boolean")
declared = record.get("declared_health")
if declared not in STATE_NUMBER:
raise ValueError(f"{service}: declared_health must be healthy, warning, or critical")
queue_depth = record.get("queue_depth")
if isinstance(queue_depth, bool) or not isinstance(queue_depth, (int, float)) or queue_depth < 0:
raise ValueError(f"{service}: queue_depth must be a non-negative number")
free_space = record.get("free_space_percent")
if isinstance(free_space, bool) or not isinstance(free_space, (int, float)) or not 0 <= free_space <= 100:
raise ValueError(f"{service}: free_space_percent must be between 0 and 100")

def classify(record):
if not record["reachable"]:
return "critical"
if record["declared_health"] == "critical":
return "critical"
if record["declared_health"] == "warning":
return "warning"
if record["queue_depth"] > 25:
return "warning"
if record["free_space_percent"] < 15:
return "warning"
return "healthy"

def render(payload):
if not isinstance(payload, dict):
raise ValueError("top-level input must be an object")
if set(payload) != set(SERVICES):
raise ValueError("input must contain exactly sonarr and radarr")
for service in SERVICES:
validate_record(service, payload[service])

lines = [
    "# HELP arr_monitor_up Whether the monitor can reach the service.",
    "# TYPE arr_monitor_up gauge",
]
for service in SERVICES:
    value = 1 if payload[service]["reachable"] else 0
    lines.append(f'arr_monitor_up{{service="{service}"}} {value}')

lines.extend([
    "# HELP arr_monitor_state_number Health state where critical=0, warning=1, healthy=2.",
    "# TYPE arr_monitor_state_number gauge",
])
for service in SERVICES:
    state = classify(payload[service])
    lines.append(f'arr_monitor_state_number{{service="{service}"}} {STATE_NUMBER[state]}')
return "\n".join(lines)

def main():
if len(sys.argv) != 2:
raise SystemExit(f"usage: {sys.argv[0]} INPUT.json")
with open(sys.argv[1], "r", encoding="utf-8") as handle:
payload = json.load(handle)
print(render(payload))

if name == "main":
main()
PY

explanation

The exporter has no external dependencies and does not contact live services.

step

3

title

Create a baseline input

command

cat > /opt/lab-classroom/class62/sample.json <<'JSON'
{
"sonarr": {
"reachable": true,
"declared_health": "healthy",
"queue_depth": 4,
"free_space_percent": 60
},
"radarr": {
"reachable": true,
"declared_health": "healthy",
"queue_depth": 2,
"free_space_percent": 55
}
}
JSON
cd /opt/lab-classroom/class62 && python3 exporter.py sample.json

explanation

The baseline must show two reachable samples with value 1 and two healthy state samples with value 2.

step

4

title

Create the exact-output verifier

command

cat > /opt/lab-classroom/class62/verify.py <<'PY'

!/usr/bin/env python3

import re
from exporter import render

SERVICES = ("sonarr", "radarr")
HELP_UP = "# HELP arr_monitor_up Whether the monitor can reach the service."
TYPE_UP = "# TYPE arr_monitor_up gauge"
HELP_STATE = "# HELP arr_monitor_state_number Health state where critical=0, warning=1, healthy=2."
TYPE_STATE = "# TYPE arr_monitor_state_number gauge"
UP_RE = re.compile(r'arr_monitor_up{service="(sonarr|radarr)"} ([01])')
STATE_RE = re.compile(r'arr_monitor_state_number{service="(sonarr|radarr)"} ([012])')

def service(reachable=True, declared="healthy", queue=0, free=50):
return {
"reachable": reachable,
"declared_health": declared,
"queue_depth": queue,
"free_space_percent": free,
}

def expected_text(up, state):
lines = [HELP_UP, TYPE_UP]
lines.extend(f'arr_monitor_up{{service="{name}"}} {up[name]}' for name in SERVICES)
lines.extend([HELP_STATE, TYPE_STATE])
lines.extend(f'arr_monitor_state_number{{service="{name}"}} {state[name]}' for name in SERVICES)
return "\n".join(lines)

def check_case(name, payload, expected_up, expected_state):
actual = render(payload)
expected = expected_text(expected_up, expected_state)
assert actual == expected, f"{name}: complete metric document differs\nEXPECTED:\n{expected}\nACTUAL:\n{actual}"

lines = actual.splitlines()
assert lines[0] == HELP_UP, f"{name}: arr_monitor_up HELP is not first"
assert lines[1] == TYPE_UP, f"{name}: arr_monitor_up TYPE is not before its samples"
assert lines[4] == HELP_STATE, f"{name}: state HELP is not before state samples"
assert lines[5] == TYPE_STATE, f"{name}: state TYPE is not before state samples"

samples = [line for line in lines if not line.startswith("#")]
assert len(samples) == 4, f"{name}: expected exactly four samples, got {len(samples)}"
expected_samples = {line for line in expected.splitlines() if not line.startswith("#")}
assert set(samples) == expected_samples, f"{name}: sample set is not exact"

up_matches = [UP_RE.fullmatch(line) for line in samples if line.startswith("arr_monitor_up{")]
state_matches = [STATE_RE.fullmatch(line) for line in samples if line.startswith("arr_monitor_state_number{")]
assert len(up_matches) == 2 and all(up_matches), f"{name}: invalid up label or value; only 0 and 1 are allowed"
assert len(state_matches) == 2 and all(state_matches), f"{name}: invalid state label or value"
assert {match.group(1) for match in up_matches} == set(SERVICES), f"{name}: up service set is incomplete"
assert {match.group(1) for match in state_matches} == set(SERVICES), f"{name}: state service set is incomplete"
print(f"PASS {name}")

CASES = [
(
"baseline healthy",
{"sonarr": service(queue=4, free=60), "radarr": service(queue=2, free=55)},
{"sonarr": 1, "radarr": 1},
{"sonarr": 2, "radarr": 2},
),
(
"unreachable is critical",
{"sonarr": service(reachable=False), "radarr": service()},
{"sonarr": 0, "radarr": 1},
{"sonarr": 0, "radarr": 2},
),
(
"reachable declared critical",
{"sonarr": service(), "radarr": service(reachable=True, declared="critical")},
{"sonarr": 1, "radarr": 1},
{"sonarr": 2, "radarr": 0},
),
(
"queue depth warning",
{"sonarr": service(queue=26), "radarr": service()},
{"sonarr": 1, "radarr": 1},
{"sonarr": 1, "radarr": 2},
),
(
"low free space warning",
{"sonarr": service(), "radarr": service(free=14.9)},
{"sonarr": 1, "radarr": 1},
{"sonarr": 2, "radarr": 1},
),
(
"warning boundaries remain healthy",
{"sonarr": service(queue=25), "radarr": service(free=15)},
{"sonarr": 1, "radarr": 1},
{"sonarr": 2, "radarr": 2},
),
]

for case in CASES:
check_case(*case)

print("PASS all 6 scenarios; metadata order and exact four-sample sets verified")
PY
cd /opt/lab-classroom/class62 && python3 verify.py

explanation

This executes the queue-depth and free-space warning branches, the reachable declared-critical branch, the unreachable branch, and both strict threshold boundaries.

step

5

title

Confirm malformed input is rejected

command

cd /opt/lab-classroom/class62 && python3 - <<'PY'
from exporter import render

bad = {
"sonarr": {
"reachable": "yes",
"declared_health": "healthy",
"queue_depth": 0,
"free_space_percent": 50
},
"radarr": {
"reachable": True,
"declared_health": "healthy",
"queue_depth": 0,
"free_space_percent": 50
}
}

try:
render(bad)
except ValueError as error:
print(f"PASS malformed input rejected: {error}")
else:
raise SystemExit("FAIL malformed input was accepted")
PY

explanation

The exporter must reject a string masquerading as a Boolean rather than treating it as a truthy value.