| 1 | /** |
| 2 | * The dispatcher for g1t.page: every app deployed by g1t is served here. |
| 3 | * |
| 4 | * The hostname's first label is the app's script name in the Workers for |
| 5 | * Platforms namespace (`web-git-fix-login-acme.g1t.page` is the fix-login |
| 6 | * branch's preview of acme's web project), so the app is fetched by name |
| 7 | * and runs only for as long as it answers. An app no one visits runs |
| 8 | * nothing and costs nothing. Each request it serves is held to |
| 9 | * `APP_LIMITS`, so one app cannot spend without bound. The one lookup is for an address an app |
| 10 | * had before its project moved: `DOMAINS` holds a redirect under the old |
| 11 | * hostname for as long as the old name is held, and it is followed before |
| 12 | * anything the old script would answer (such as a paused notice). |
| 13 | * |
| 14 | * Any other hostname is a project's custom domain, reaching here through |
| 15 | * Cloudflare for SaaS: the `DOMAINS` KV namespace, written by the |
| 16 | * deployments service, names its app, or the hostname it redirects to. |
| 17 | * |
| 18 | * Kept apart from g1t.sh, so apps share no cookies or origin with the site |
| 19 | * people sign in to. |
| 20 | */ |
| 21 | |
| 22 | import { |
| 23 | APP_LIMITS, |
| 24 | DOMAIN, |
| 25 | FALLBACK, |
| 26 | REQUEST_ID_HEADER, |
| 27 | REQUEST_MARK, |
| 28 | overLimits, |
| 29 | parseEntry, |
| 30 | redirectTo, |
| 31 | route, |
| 32 | traceFor, |
| 33 | type AppTelemetry, |
| 34 | type DomainEntry, |
| 35 | } from "./route.ts"; |
| 36 | |
| 37 | type Env = { |
| 38 | APPS: DispatchNamespace; |
| 39 | /** Custom hostname, or an app's old g1t.page hostname, to `{ script, redirect }`. */ |
| 40 | DOMAINS?: KVNamespace; |
| 41 | }; |
| 42 | |
| 43 | /** How long a custom hostname's entry is kept in this isolate and at the edge. */ |
| 44 | const ENTRY_TTL_MS = 60 * 1000; |
| 45 | const entries = new Map<string, { at: number; entry: DomainEntry | null }>(); |
| 46 | |
| 47 | function page(status: number, title: string, body: string, site = DOMAIN): Response { |
| 48 | const html = `<!doctype html> |
| 49 | <html lang="en"> |
| 50 | <head> |
| 51 | <meta charset="utf-8"> |
| 52 | <meta name="viewport" content="width=device-width, initial-scale=1"> |
| 53 | <meta name="robots" content="noindex"> |
| 54 | <title>${escape(title)} · ${escape(site)}</title> |
| 55 | <style> |
| 56 | :root { color-scheme: dark; --bg: #121214; --fg: #ececf1; --muted: #9a9aa6; --accent: #b4a7f5; } |
| 57 | body { margin: 0; min-height: 100vh; display: grid; place-items: center; background: var(--bg); color: var(--fg); |
| 58 | font: 16px/1.6 ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif; padding: 0 16px; } |
| 59 | main { max-width: 32rem; } |
| 60 | h1 { font-size: 1.5rem; margin: 0 0 .5rem; letter-spacing: -.01em; } |
| 61 | p { color: var(--muted); margin: .5rem 0; } |
| 62 | a { color: var(--accent); } |
| 63 | code { font: .9em ui-monospace, SFMono-Regular, Menlo, monospace; color: var(--fg); } |
| 64 | </style> |
| 65 | </head> |
| 66 | <body><main><h1>${escape(title)}</h1>${body}</main></body> |
| 67 | </html>`; |
| 68 | return new Response(html, { |
| 69 | status, |
| 70 | headers: { "content-type": "text/html; charset=utf-8", "x-robots-tag": "noindex", "cache-control": "no-store" }, |
| 71 | }); |
| 72 | } |
| 73 | |
| 74 | function escape(text: string): string { |
| 75 | return text.replace(/[&<>"']/g, (c) => `&#${c.charCodeAt(0)};`); |
| 76 | } |
| 77 | |
| 78 | /** A custom hostname's entry: from this isolate, else KV (cached at the edge too). */ |
| 79 | async function lookup(env: Env, hostname: string): Promise<DomainEntry | null> { |
| 80 | const cached = entries.get(hostname); |
| 81 | if (cached && Date.now() - cached.at < ENTRY_TTL_MS) return cached.entry; |
| 82 | const value = env.DOMAINS ? await env.DOMAINS.get(hostname, { type: "json", cacheTtl: ENTRY_TTL_MS / 1000 }) : null; |
| 83 | const entry = parseEntry(value); |
| 84 | entries.set(hostname, { at: Date.now(), entry }); |
| 85 | if (entries.size > 5000) entries.delete(entries.keys().next().value!); |
| 86 | return entry; |
| 87 | } |
| 88 | |
| 89 | /** |
| 90 | * Runs the app `script` for the request; `shown` is the address named in |
| 91 | * its error pages. Each request gets an id and a trace, handed to the app |
| 92 | * (`x-g1t-request-id`, `traceparent`), and one line naming them, the app |
| 93 | * and its project (`telemetry`), which observability reads from this |
| 94 | * Worker's tail events and files with what the app's own tell it. |
| 95 | */ |
| 96 | async function dispatch(env: Env, request: Request, script: string, shown: string, missing: () => Response, telemetry: AppTelemetry | null): Promise<Response> { |
| 97 | const { id, trace, traceparent } = traceFor(request.headers.get("traceparent")); |
| 98 | console.log(REQUEST_MARK, { id, script, trace_id: trace, app: telemetry }); |
| 99 | const headers = new Headers(request.headers); |
| 100 | headers.set(REQUEST_ID_HEADER, id); |
| 101 | headers.set("traceparent", traceparent); |
| 102 | request = new Request(request, { headers }); |
| 103 | let app: Fetcher; |
| 104 | try { |
| 105 | app = env.APPS.get(script, {}, { limits: APP_LIMITS }); |
| 106 | } catch { |
| 107 | return missing(); |
| 108 | } |
| 109 | try { |
| 110 | return await app.fetch(request); |
| 111 | } catch (error) { |
| 112 | if (/worker not found|script not found|does not exist/i.test(String(error))) return missing(); |
| 113 | if (overLimits(error)) { |
| 114 | return page( |
| 115 | 503, |
| 116 | "The app went over its limits", |
| 117 | `<p>The app at <code>${escape(shown)}</code> used more than ${APP_LIMITS.cpuMs} ms of CPU time, or made more than ${APP_LIMITS.subRequests} requests of its own, answering this request.</p>`, |
| 118 | shown, |
| 119 | ); |
| 120 | } |
| 121 | return page(502, "The app failed", `<p>The app at <code>${escape(shown)}</code> threw an error before it could answer.</p>`, shown); |
| 122 | } |
| 123 | } |
| 124 | |
| 125 | export default { |
| 126 | async fetch(request: Request, env: Env): Promise<Response> { |
| 127 | const host = new URL(request.url).hostname; |
| 128 | const where = route(host); |
| 129 | switch (where.kind) { |
| 130 | case "home": |
| 131 | return page( |
| 132 | 200, |
| 133 | "g1t.page", |
| 134 | `<p>Apps deployed by <a href="https://g1t.sh">g1t</a>: every pull request's preview, and each repository's production.</p> |
| 135 | <p><a href="https://docs.g1t.sh/guides/deployments/">How deployments work</a></p>`, |
| 136 | ); |
| 137 | case "fallback": |
| 138 | return page( |
| 139 | 200, |
| 140 | "Custom domains on g1t", |
| 141 | `<p>Point a custom domain here, with a CNAME to <code>${FALLBACK}</code>, to serve a project's production on it. Add the domain first, under the project's Settings, Deployments, on g1t.</p> |
| 142 | <p><a href="https://docs.g1t.sh/guides/deployments/#custom-domains">How custom domains work</a></p>`, |
| 143 | ); |
| 144 | case "invalid": |
| 145 | return page(404, "Nothing here", "<p>This is not the address of an app on g1t.page.</p>"); |
| 146 | case "custom": |
| 147 | return custom(request, env, where.hostname); |
| 148 | case "app": { |
| 149 | const label = where.label; |
| 150 | // An address the app had before its project moved (its workspace or |
| 151 | // repository was renamed or transferred) redirects to where it is |
| 152 | // now, whatever the app it named answers, paused or not. |
| 153 | const { moved, telemetry } = await appRedirect(request, env, label); |
| 154 | if (moved) return moved; |
| 155 | let response = await dispatch(env, request, label, `${label}.${DOMAIN}`, () => missing(label), telemetry); |
| 156 | // Previews are for the people reviewing a change, not search engines. |
| 157 | if (isPreview(label)) { |
| 158 | response = new Response(response.body, response); |
| 159 | response.headers.set("x-robots-tag", "noindex"); |
| 160 | } |
| 161 | return response; |
| 162 | } |
| 163 | } |
| 164 | }, |
| 165 | } satisfies ExportedHandler<Env>; |
| 166 | |
| 167 | /** |
| 168 | * The redirect for an app's old address, if the deployments service left |
| 169 | * one (in `DOMAINS`, under the old hostname, as `{ script, redirect }`), |
| 170 | * else null. A lookup that fails serves the app as it is rather than an |
| 171 | * error. |
| 172 | */ |
| 173 | async function appRedirect(request: Request, env: Env, label: string): Promise<{ moved: Response | null; telemetry: AppTelemetry | null }> { |
| 174 | const hostname = `${label}.${DOMAIN}`; |
| 175 | let entry: DomainEntry | null; |
| 176 | try { |
| 177 | entry = await lookup(env, hostname); |
| 178 | } catch (error) { |
| 179 | console.error("could not read redirect", label, error); |
| 180 | return { moved: null, telemetry: null }; |
| 181 | } |
| 182 | // Otherwise the entry is the app's own: what its requests are filed under. |
| 183 | if (!entry?.redirect || entry.redirect === hostname) return { moved: null, telemetry: entry?.telemetry ?? null }; |
| 184 | const moved = new Response(null, { |
| 185 | status: 301, |
| 186 | headers: { |
| 187 | location: redirectTo(request.url, entry.redirect), |
| 188 | "x-robots-tag": "noindex", |
| 189 | "cache-control": "public, max-age=3600", |
| 190 | }, |
| 191 | }); |
| 192 | return { moved, telemetry: null }; |
| 193 | } |
| 194 | |
| 195 | /** A custom domain: its app, or a 308 to the hostname it is paired with. */ |
| 196 | async function custom(request: Request, env: Env, hostname: string): Promise<Response> { |
| 197 | let entry: DomainEntry | null; |
| 198 | try { |
| 199 | entry = await lookup(env, hostname); |
| 200 | } catch (error) { |
| 201 | console.error("could not read domain", hostname, error); |
| 202 | return page(503, "Try again in a moment", `<p><code>${escape(hostname)}</code> could not be looked up just now.</p>`, hostname); |
| 203 | } |
| 204 | if (!entry) { |
| 205 | return page( |
| 206 | 404, |
| 207 | "This domain is not set up", |
| 208 | `<p><code>${escape(hostname)}</code> points at g1t, but no project serves it. Its owner adds it under the project's Settings, Deployments, on <a href="https://g1t.sh">g1t</a>.</p>`, |
| 209 | hostname, |
| 210 | ); |
| 211 | } |
| 212 | if (entry.redirect && entry.redirect !== hostname) { |
| 213 | return new Response(null, { |
| 214 | status: 308, |
| 215 | headers: { location: redirectTo(request.url, entry.redirect), "cache-control": "public, max-age=300" }, |
| 216 | }); |
| 217 | } |
| 218 | // The app's own entry names its project, for observability. |
| 219 | const own = await lookup(env, `${entry.script}.${DOMAIN}`).catch(() => null); |
| 220 | return dispatch( |
| 221 | env, |
| 222 | request, |
| 223 | entry.script, |
| 224 | hostname, |
| 225 | () => |
| 226 | page( |
| 227 | 404, |
| 228 | "Nothing deployed here yet", |
| 229 | `<p><code>${escape(hostname)}</code> serves a project's production, and it is not up. Deploying the project brings it here.</p>`, |
| 230 | hostname, |
| 231 | ), |
| 232 | own?.redirect ? null : (own?.telemetry ?? null), |
| 233 | ); |
| 234 | } |
| 235 | |
| 236 | /** A branch's preview: `<project>-git-<branch>-<workspace>`. */ |
| 237 | function isPreview(label: string): boolean { |
| 238 | return label.includes("-git-"); |
| 239 | } |
| 240 | |
| 241 | function missing(label: string): Response { |
| 242 | const preview = isPreview(label); |
| 243 | return page( |
| 244 | 404, |
| 245 | preview ? "This preview is not up" : "Nothing deployed here", |
| 246 | preview |
| 247 | ? `<p>A preview comes down when its pull request is closed or merged, or after its project's idle days without a visit. Pushing to the branch, or redeploying it from the project's Deployments page, brings it back.</p>` |
| 248 | : `<p>No app is deployed at <code>${escape(label)}.${DOMAIN}</code>. Deployments are turned on per project, from its Settings on g1t.</p>`, |
| 249 | ); |
| 250 | } |