11-crontab

Crontab — Periodic Job Scheduler

A cron-like scheduler where each job runs as its own isolated process. Four jobs fire at different intervals using time.after() + channel.select. Demonstrates that spawning multiple processes is lightweight — each job is a process.service with its own PID, timer loop, and execution counter.

Architecture

wippy run
│
├── app:heartbeat  {0x00006}  ── timer 1s ──▶ TICK ──▶ reset timer ──▶ ...
├── app:cleanup    {0x00004}  ── timer 3s ──▶ TICK ──▶ reset timer ──▶ ...
├── app:report     {0x00003}  ── timer 5s ──▶ TICK ──▶ reset timer ──▶ ...
└── app:backup     {0x00008}  ── timer 7s ──▶ TICK ──▶ reset timer ──▶ ...

Each job is a separate process with its own PID. All 4 share a single source file (jobs.lua) but use different method: entry points. Processes are cheap — no reason to cram everything into one.

Project Structure

11-crontab/
├── wippy.lock
└── src/
    ├── _index.yaml       # Registry: process host, 4 job processes + 4 services
    └── jobs.lua          # Shared job loop with 4 exported methods

Registry Entries

Entry	Kind	Purpose
app:processes	process.host	Worker pool for job processes
app:heartbeat_process	process.lua	Heartbeat job (method: heartbeat)
app:heartbeat	process.service	Auto-starts heartbeat
app:cleanup_process	process.lua	Cleanup job (method: cleanup)
app:cleanup	process.service	Auto-starts cleanup
app:report_process	process.lua	Report job (method: report)
app:report	process.service	Auto-starts report
app:backup_process	process.lua	Backup job (method: backup)
app:backup	process.service	Auto-starts backup

Running

cd examples/11-crontab
wippy init
wippy run
# Watch logs — 4 processes fire at different intervals
# Ctrl+C to stop (each job logs its run count)

Output (logs):

INFO  Job started       name=heartbeat  interval=1s  pid={app:processes|0x00006}
INFO  Job started       name=cleanup    interval=3s  pid={app:processes|0x00004}
INFO  Job started       name=report     interval=5s  pid={app:processes|0x00003}
INFO  Job started       name=backup     interval=7s  pid={app:processes|0x00008}
INFO  TICK heartbeat    run=1
INFO  TICK heartbeat    run=2
INFO  TICK cleanup      run=1
INFO  TICK heartbeat    run=3
INFO  TICK heartbeat    run=4
INFO  TICK report       run=1
INFO  TICK heartbeat    run=5
INFO  TICK cleanup      run=2
INFO  TICK heartbeat    run=6
INFO  TICK backup       run=1
...
INFO  Job stopped       name=heartbeat  runs=11
INFO  Job stopped       name=report     runs=2
INFO  Job stopped       name=cleanup    runs=3
INFO  Job stopped       name=backup     runs=1

Jobs

Job	Interval	Description
heartbeat	1s	System health check
cleanup	3s	Temp file cleanup
report	5s	Usage report
backup	7s	Incremental backup

Key Concepts

• One process per job — each job runs in its own process with an isolated timer loop. Processes are lightweight in Wippy, so there's no reason to multiplex jobs into a single process.
• Shared source, multiple methods — all 4 jobs use source: file://jobs.lua but reference different method: entry points (heartbeat, cleanup, report, backup). One file, four processes.
• time.after(interval) — creates a one-shot timer channel. Not periodic — must create a new timer after each firing. The pattern is: wait for timer, handle tick, reset timer.
• channel.select with timer + events — each job selects on its timer and process.events(). When the timer fires, it ticks. When CANCEL arrives (Ctrl+C), it logs final stats and exits.
• process.service with auto_start — all 4 jobs start automatically with wippy run. No orchestrator needed.