build: add Fly.io deployment process

fly.toml (Dockerfile.web, scale-to-zero in syd, /api/health checks),
make deploy / deploy-status targets, a Gitea workflow deploying on v*
tags or manual dispatch via FLY_API_TOKEN, and README instructions
covering first-time setup and the server's runtime env knobs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.gitea/workflows/deploy.yml

@@ -0,0 +1,27 @@
+name: Deploy
+
+# Deploys the web server to Fly.io.
+# Triggers: pushing a version tag (v*), or manual dispatch.
+# Requires the FLY_API_TOKEN repository secret (create with
+# `flyctl tokens create deploy -x 999999h`).
+
+on:
+  push:
+    tags: ["v*"]
+  workflow_dispatch:
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install flyctl
+        run: |
+          curl -L https://fly.io/install.sh | sh
+          echo "$HOME/.fly/bin" >> "$GITHUB_PATH"
+
+      - name: Deploy
+        run: flyctl deploy --remote-only
+        env:
+          FLY_API_TOKEN: ${{ secrets.FLY_API_TOKEN }}

Makefile

@@ -4,7 +4,7 @@ BUILD_DIR=bin
 GO=go
 GOFLAGS=-v
 
-.PHONY: build build-server build-all test lint clean cover
+.PHONY: build build-server build-all test lint clean cover deploy deploy-status
 
 build:
 	$(GO) build $(GOFLAGS) -o $(BUILD_DIR)/$(BINARY_NAME) ./cmd/exploredns
@@ -27,3 +27,12 @@ lint:
 clean:
 	rm -rf $(BUILD_DIR)
 	rm -f coverage.out coverage.html
+
+# Deploy the web server to Fly.io (requires flyctl and a configured app;
+# see "Deploying to Fly.io" in README.md).
+deploy:
+	flyctl deploy --remote-only
+
+deploy-status:
+	flyctl status
+	flyctl checks list

README.md

@@ -246,6 +246,54 @@ data: {}
 
 Completed jobs are kept in memory for one hour before being purged.
 
+### Server configuration
+
+The server is safe to expose publicly by default and reads these environment
+variables at startup:
+
+| Variable | Default | Meaning |
+|---|---|---|
+| `EXPLOREDNS_JOB_TIMEOUT` | `5m` | Hard deadline per traversal (Go duration). Timed-out jobs report `error` with any partial results. |
+| `EXPLOREDNS_MAX_JOBS` | `8` | Maximum concurrent traversals; further `POST /api/traverse` requests get `429`. |
+| `EXPLOREDNS_CORS_ORIGIN` | *(unset)* | Off by default (the SPA is same-origin). Set an origin — or `*` for development — to enable cross-origin API access. |
+
+---
+
+## Deploying to Fly.io
+
+The repo ships a [fly.toml](fly.toml) that builds `Dockerfile.web` and runs
+the web server with scale-to-zero machines in `syd` (edit `app` /
+`primary_region` to taste).
+
+### First-time setup
+
+```sh
+flyctl auth login
+flyctl apps create exploredns   # match the app name in fly.toml
+make deploy                     # flyctl deploy --remote-only
+```
+
+`make deploy-status` shows machine and health-check state.  The app serves
+the SPA at `https://<app>.fly.dev/` with `/api/health` as the health check.
+
+### Continuous deployment
+
+`.gitea/workflows/deploy.yml` deploys on any `v*` tag push (or manual
+dispatch).  It needs a `FLY_API_TOKEN` repository secret:
+
+```sh
+flyctl tokens create deploy -x 999999h
+```
+
+### Notes
+
+- Traversal traffic is outbound UDP/TCP port 53, which Fly machines allow;
+  upstream root discovery uses Fly's internal resolver via `/etc/resolv.conf`
+  and falls back to the built-in IANA root hints.
+- The job timeout, job cap, and same-origin CORS defaults above are what make
+  unauthenticated public exposure reasonable; tighten `EXPLOREDNS_MAX_JOBS`
+  if the app attracts traffic.
+
 ---
 
 

fly.toml

@@ -0,0 +1,34 @@
+# Fly.io configuration for the ExploreDNS web server.
+# Deploy with `make deploy` (or `flyctl deploy --remote-only`).
+# First-time setup: see "Deploying to Fly.io" in README.md.
+
+app = "exploredns"
+primary_region = "syd"
+
+[build]
+  dockerfile = "Dockerfile.web"
+
+[env]
+  # Public-exposure guards (web/api reads these at startup).
+  EXPLOREDNS_JOB_TIMEOUT = "5m"
+  EXPLOREDNS_MAX_JOBS = "8"
+
+[http_service]
+  internal_port = 8080
+  force_https = true
+  # Scale to zero when idle; SSE streams count as active connections,
+  # so machines are not stopped mid-traversal.
+  auto_stop_machines = "stop"
+  auto_start_machines = true
+  min_machines_running = 0
+
+  [[http_service.checks]]
+    interval = "30s"
+    timeout = "5s"
+    grace_period = "10s"
+    method = "GET"
+    path = "/api/health"
+
+[[vm]]
+  size = "shared-cpu-1x"
+  memory = "256mb"