Erich Blume
6636576cdc
Block recursive crawler paths caused by SPA fallback + relative links: /tags/ depth >1 returns 404, global depth ≥5 returns 404. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
105 lines
5.1 KiB
Markdown
105 lines
5.1 KiB
Markdown
---
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title: Fly.io Proxy
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modified: 2026-02-08
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tags:
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- service
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- networking
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- fly-io
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---
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# Fly.io Proxy
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Public reverse proxy on [Fly.io](https://fly.io) that exposes selected BlumeOps services to the internet via a Tailscale tunnel back to the homelab.
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## Quick Reference
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| Property | Value |
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|----------|-------|
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| **App** | `blumeops-proxy` |
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| **Region** | `sjc` (San Jose) |
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| **Fly.io URL** | `blumeops-proxy.fly.dev` |
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| **Config** | `fly/` directory in repo |
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| **IaC** | `fly/fly.toml` (app), Pulumi (DNS + auth key) |
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## Exposed Services
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| Public domain | Backend | Service |
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|---------------|---------|---------|
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| `docs.eblu.me` | `docs.tail8d86e.ts.net` | [[docs]] |
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## Architecture
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Internet traffic hits Fly.io's Anycast edge, terminates TLS with a Let's Encrypt certificate, and is proxied by nginx to the backend service over a Tailscale WireGuard tunnel. See [[expose-service-publicly]] for the full architecture diagram.
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## Key Files
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| File | Purpose |
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|------|---------|
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| `fly/fly.toml` | App configuration |
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| `fly/Dockerfile` | nginx + Tailscale + Alloy container |
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| `fly/nginx.conf` | Reverse proxy, caching, rate limiting, JSON logging |
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| `fly/alloy.river` | Alloy config: log tailing, metric extraction, remote_write |
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| `fly/start.sh` | Entrypoint: start Tailscale, Alloy, then nginx |
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| `pulumi/tailscale/__main__.py` | Auth key (`tag:flyio-proxy`) |
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| `pulumi/tailscale/policy.hujson` | ACL grants for proxy |
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| `pulumi/gandi/__main__.py` | DNS CNAMEs |
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## Networking
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Fly.io runs Firecracker microVMs which support TUN devices natively. Tailscale runs with a real TUN interface (not userspace networking), so MagicDNS and direct Tailscale IP routing work normally.
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The Tailscale auth key is `preauthorized=True` to avoid device approval hangs on container restarts.
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## Observability
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[[alloy|Alloy]] runs inside the container alongside nginx and Tailscale, providing:
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- **Logs**: nginx JSON access logs tailed and pushed to [[loki|Loki]] (`{instance="flyio-proxy", job="flyio-nginx"}`)
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- **Metrics**: Derived from access logs, pushed to [[prometheus|Prometheus]] via `remote_write`
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- `flyio_nginx_http_requests_total` — request rate by status/method/host
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- `flyio_nginx_http_request_duration_seconds` — latency histogram
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- `flyio_nginx_http_response_bytes_total` — response bandwidth
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- `flyio_nginx_cache_requests_total` — cache HIT/MISS/EXPIRED counts
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### Dashboards
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| Dashboard | Purpose |
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|-----------|---------|
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| **Docs APM** | Per-service view for `docs.eblu.me`: request rate, latency percentiles, cache hit ratio, error rate, bandwidth, access logs |
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| **Fly.io Proxy Health** | Aggregate proxy health: connections, total request rate by host, cache performance, upstream latency, Alloy health |
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Alloy listens on `127.0.0.1:12345` for self-scraping its `/metrics` endpoint. All metrics carry `instance="flyio-proxy"`.
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## Security Considerations
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The `tag:flyio-proxy` ACL grants access only to `tag:flyio-target:443`. Services must explicitly opt in by adding a `tailscale.com/tags: "tag:k8s,tag:flyio-target"` annotation to their Tailscale Ingress. This means the proxy can only reach endpoints that have been individually tagged — a compromised nginx config cannot route to arbitrary services on the tailnet.
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Currently tagged as `tag:flyio-target`: [[docs]], [[loki]], [[prometheus]]. Loki and Prometheus are tagged so that [[alloy|Alloy]] (running inside the container) can push logs and metrics directly via their Tailscale Ingress endpoints — the restricted ACL means Caddy on indri (`tag:homelab`) is not reachable from the proxy.
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To expose an additional service through the proxy, add the `tag:flyio-target` annotation to its Tailscale Ingress. See [[expose-service-publicly]] for the full workflow.
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## Spider Trap Mitigation
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The SPA fallback (`try_files ... /index.html`) serves `index.html` with a 200 for *any* URI, including non-existent paths. Quartz's relative links (`../path`) compound when resolved from phantom URLs, creating an infinite tree of unique URIs that crawlers follow indefinitely. In March 2026, Meta's crawler (`meta-externalagent/1.1`) hit ~49,000 unique URIs over 7 hours this way.
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Two nginx `location` guards in `containers/quartz/default.conf` mitigate the trap:
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1. **`/tags/` depth limit** — `/tags/<name>` is always flat; anything deeper returns 404.
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2. **Global depth-5 cutoff** — real content never exceeds depth 4; paths with 5+ segments return 404.
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These are applied in the Quartz container's nginx config, not the Fly.io proxy. The proper fix is switching Quartz to root-absolute links (planned for the fork).
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## Secrets
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| Secret | Source | Description |
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|--------|--------|-------------|
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| `TS_AUTHKEY` | Pulumi state → `fly secrets` | Tailscale auth key for joining tailnet |
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| `FLY_DEPLOY_TOKEN` | Fly.io → 1Password | Deploy token for CI |
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## Related
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- [[expose-service-publicly]] - Setup guide for adding new public services
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- [[manage-flyio-proxy]] - Operational tasks (deploy, shutoff, troubleshoot)
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- [[caddy]] - Private reverse proxy for `*.ops.eblu.me` (separate system)
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- [[tailscale]] - WireGuard mesh network
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- [[gandi]] - DNS hosting
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