Migrating bmf-tech.com from gobel to gohan

Background

bmf-tech.com has gone through four infrastructure generations.

1. WordPress — Abandoned after maintenance overhead and security patches became unsustainable.
2. Rubel — A headless CMS built with Laravel. Ran a React frontend with MySQL on a ConoHa VPS.
3. gobel — A full rewrite of Rubel in Go. Ran for several years and accumulated over 700 articles. The backend used nginx, MySQL, and Redis via Docker Compose; the frontend used Vue.js. A monitoring stack with Prometheus, Grafana, Loki, and Pyroscope was also in place.
4. gohan — A Go-based SSG. Builds from Markdown files in content/en/ and content/ja/, with GitHub Actions running the build and Cloudflare Pages serving the output. Serverless with zero running cost.

The goal was to bring server cost and operational load down to zero. I wanted a setup where pushing to GitHub triggers an automatic build and deploy, with the entire site built from Markdown files.

Migration Phases

I planned the migration in 12 phases.

Phase 3: English Slug Generation

The original gobel database had no slug column. URLs used URL-encoded Japanese titles — for example /posts/Go%E3%81%A7HTTP%E3%82%B5%E3%83%BC%E3%83%90%E3%83%BC%E3%82%92%E6%9B%B8%E3%81%8F. After the migration, I wanted clean English slugs like /posts/go-http-server/.

Writing slugs for 700+ articles by hand was impractical, so I fed batches of (id, title) pairs to Claude to generate English slug candidates at scale. I exported the output to slug_map.csv for manual review, checking for duplicates and confirming meaning.

Phase 4: Migration Script

The Go migration tool took two inputs — a MySQL dump and slug_map.csv — and produced two outputs.

• content/ja/posts/*.md — One Markdown file per article, with frontmatter generated from the posts, categories, and tag_post tables.
• _redirects — A 301 redirect rule file in Cloudflare Pages format, mapping old URLs to new ones.

One issue came up during _redirects generation. Cloudflare Pages receives request paths in percent-encoded form, so the script had to apply url.PathEscape() to the old URLs. Writing raw Japanese strings in the rules caused redirects to stop working.

Phase 6: Image Asset Migration

All images on the original site lived on external CDNs, primarily Qiita Image Store. A download tool scanned each article's Markdown, saved images under assets/images/posts/{slug}/, and rewrote ![alt](url) references to local paths.

Phase 9.5: Preflight Checker

Before the DNS switch, a Go preflight tool sent HTTP requests to every article URL against the Cloudflare Pages preview URL and verified HTTP 200 responses. It also confirmed every rule in _redirects returned a 301. This gave confidence that no articles would 404 after the DNS cutover.

Phase 11: DNS Migration

I moved the nameservers from ConoHa to Cloudflare. Cloudflare Pages now serves gohan's static output directly from its CDN. www.bmf-tech.com runs zero server-side code.

Phase 12: ConoHa VPS Shutdown

After confirming index coverage trends in Google Search Console, I shut down the ConoHa VPS that had been running the gobel API and MySQL. Monthly VPS cost dropped to zero.

Post-Migration Setup

gohan now generates the site from Markdown files in content/en/ and content/ja/. Pushing to GitHub triggers GitHub Actions to build and deploy to Cloudflare Pages. A full build of 584+ EN and 584+ JA articles, including OGP image generation, completes in under 60 seconds.

Defining 301 redirects from old URLs to new ones in _redirects kept the SEO impact low. Index coverage remained stable in Google Search Console after the DNS migration.

What Changed

• Writing environment — Switched from a custom web admin panel to local editing in VS Code. Articles are now version-controlled in Git.
• Quality control — textlint runs in CI via GitHub Actions, catching inconsistent phrasing and style rule violations on every push.
• Metadata management — Front Matter now explicitly sets title, description, categories, tags, and OGP fields for every article. gobel saw none of this.
• Self-hosted images — Images depended on external CDNs such as Qiita Image Store. They are now managed as static assets under assets/images/posts/{slug}/, eliminating the risk of losing images if an external service shuts down.
• Slug-based URLs — Article URLs changed from percent-encoded Japanese titles to English slug format (e.g., /posts/go-http-server/), improving readability and shareability.
• i18n — The site now has a two-language structure with content/ja/ and content/en/, with articles linked via translation_key.
• Hosting — Moved from a self-managed ConoHa VPS to Cloudflare Pages. Static content comes from a CDN with a generous free tier, so there are no ongoing server costs.
• Custom pages — Added a bookshelf page for tracking books read and an Amazon Associate link generator page.

Summary

Since the migration, the site has been running stably and comfortably. Writing and pushing an article is all it takes to deploy — no server maintenance required. Looking back, I wish I had made the switch to an SSG sooner.

I made heavy use of AI throughout the development. The project had been sitting idle for a long time despite having a rough design in place, but with AI help I was able to move through both the blog system development and the migration at a pace I would not have managed otherwise. The small scale of the system helped, but without AI the effort would have been far greater. I almost feel glad I waited until AI was available before starting.

Both the source code and the articles are fully public.

• bmf-tech source: bmf-san/bmf-tech
• gohan: bmf-san/gohan