Java: Health Checks

Your task is to fix the health checks tool so that every command updates the data correctly and prints the correct success message or error reason. It reads the state from data/health.json, processes the check, mute and unmute commands, and writes the updated state back.

Project Structure

├── data/
│   └── health.json             # Persistent monitor state (every service's streaks and status)
├── src/
│   ├── main/java/com/health/
│   │   ├── Commands.java       # Command handlers
│   │   ├── FileIo.java         # State file load and save
│   │   ├── Main.java           # CLI entry point
│   │   ├── Models.java         # Data models
│   │   └── Parser.java         # JSON parsing
│   └── test/java/com/health/
│       └── CommandsTest.java
├── health                      # CLI launcher script
├── run.sh                      # Setup and run script
├── reset.sh                    # Restore data/health.json to its initial state
├── test.sh                     # Test script (writes junit.xml)
├── pom.xml                     # Maven build configuration
└── README.md

Commands

Install

mvn -B -ntp -DskipTests package

Run

bash run.sh

Test

bash test.sh

Reset

Restore data/health.json to its initial state.

bash reset.sh

Examples

Each example below runs independently against the initial data/health.json and shows only the records it changes.

Example 1: A good ping extends the pass streak

Command:

./health check api up

Output:

api up (10 in a row)

Changed records in data/health.json:

{"service":"api","status":"ok","fails_in_row":0,"passes_in_row":10,"muted":false,"alerts":2}

Example 2: A result the monitor does not record is rejected

Command:

./health check api sideways

Output:

Error: INVALID_RESULT

data/health.json: unchanged.

Example 3: Muting a service silences its alerts

Command:

./health mute notify

Output:

notify muted

Changed records in data/health.json:

{"service":"notify","status":"ok","fails_in_row":1,"passes_in_row":0,"muted":true,"alerts":0}

Example 4: Turning alerts back on does not page for an outage already running

Command:

./health unmute search

Output:

search unmuted

Changed records in data/health.json:

{"service":"search","status":"alerting","fails_in_row":5,"passes_in_row":0,"muted":false,"alerts":4}

Example 5: A service that was never checked is not found

Command:

./health mute ghost-service

Output:

Error: SERVICE_NOT_FOUND

data/health.json: unchanged.