🔌 Wiring Haskell Executables for Production Scheduled Tasks
🎯 The Goal
🚀 The Haskell port had 32 library modules and 67 passing tests, but the two executables were still stubs.
🔧 The user wanted to wire them up and point the GitHub Actions workflows at the Haskell implementations.
🔄 The switch needed to be easily reversible, a simple workflow file revert to fall back to TypeScript.
🏗️ What Got Wired
🕐 The RunScheduled executable now implements the full task dispatch loop from the TypeScript run-scheduled script.
📋 It parses command line arguments for hour and task overrides, resolves the Pacific time zone hour, and runs each scheduled task with thirty-second inter-task delays.
⚡ Three task runners are fully functional: blog series generation, AI fiction, and reflection title generation.
🤖 Blog series generation calls Gemini with model fallback chains, parses the generated markdown, writes frontmatter with navigation links, updates previous posts, syncs to the Obsidian vault, and updates the daily reflection.
🐲 AI fiction pulls the daily reflection from the vault, checks whether fiction already exists, calls Gemini, and writes the updated content back.
🏷️ Reflection title generation tries today first and then yesterday, extracting recent creative titles for style reference before calling Gemini.
⚠️ Gracefully Stubbed Tasks
📸 Image backfill logs a skip message because the image generation pipeline requires multiple external providers that are not yet ported.
🔗 Internal linking logs a skip because the BFS wikilink insertion requires Gemini-powered content analysis that is not yet ported.
📱 Social posting logs a skip because Twitter, Bluesky, and Mastodon posting APIs are not yet ported.
🔔 Each stubbed task produces clear log output so operators know what was skipped and why.
🔧 The InjectGiscus Executable
💬 The inject-giscus executable is fully functional, implementing the complete static comment injection pipeline.
🌐 It fetches all Giscus discussions from the GitHub GraphQL API, builds a comment map keyed by pathname and slug, walks the public HTML directory, and injects static comment sections into each page.
🔍 This improves SEO by making discussion content visible to search crawlers that cannot execute JavaScript.
🔀 Workflow Changes
🏗️ The Haskell CI workflow now builds both executables and uploads them as a single artifact with 90 day retention.
⬇️ The scheduled and deploy workflows download pre-built binaries from the latest successful Haskell CI run, so no compilation happens at runtime.
📝 The scheduled workflow uses the GitHub CLI to find the latest successful haskell.yml run and downloads the run-scheduled binary.
🚢 The deploy workflow similarly downloads the inject-giscus binary and runs it against the public directory after the Quartz build.
🔙 Rolling back is a workflow file revert, restoring the npx tsx command.
📦 The TypeScript code is completely untouched, ready to be swapped back in at any time.
🐛 Critical Bug Fix: Process Cleanup Self-Termination
🔪 The initial run crashed with exit code 143, meaning the process received SIGTERM and terminated itself.
🔍 The root cause was in the findObProcesses function which builds a grep pattern using foldr to join with pipes, but produced a trailing empty alternative that matched every process.
💥 With the pattern obsidian-headless followed by a pipe and an empty string, the regular expression matched all user processes including the scheduler itself.
🔧 The fix replaced the foldr join with a proper intercalation function that produces no trailing pipe.
🛡️ Additionally, the self-process PID is now filtered from the kill list using getProcessID from System.Posix.Process, matching the TypeScript protection.
🔌 A third fix corrected runObCommand which accepted environment variables and working directory parameters but silently ignored them, now using readCreateProcessWithExitCode with proper proc configuration.
🧪 Verification
✅ All 67 Haskell tests pass across 10 test suites.
✅ All 1298 TypeScript tests pass, confirming no regressions.
🏗️ Both executables compile cleanly with zero warnings on GHC 9.14.1.
🧠 Design Decisions
🏛️ The repo root is resolved from the REPO_ROOT environment variable, then GITHUB_WORKSPACE, then falls back to the parent directory since the executable runs from the haskell subdirectory.
🔄 The Gemini caller function bridges the library module callbacks with the actual HTTP client, combining system and user prompts into a single text payload.
📊 The task runner collects success and failure results in a list, printing a summary table at the end with success counts and error messages.
📚 Book Recommendations
🔍 Similar
- 📖 Production Haskell by Matt Parsons
- 📖 Haskell in Depth by Vitaly Bragilevsky
🔄 Contrasting
- 📖 Continuous Delivery by Jez Humble and David Farley
- 📖 Infrastructure as Code by Kief Morris
🎨 Creatively Related
- 📖 The Art of Unix Programming by Eric S Raymond
- 📖 Designing Data-Intensive Applications by Martin Kleppmann