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| 1 | +import { type ActionFunctionArgs, type LoaderFunctionArgs } from "@remix-run/server-runtime"; |
| 2 | +import { env } from "~/env.server"; |
| 3 | +import { getRequestAbortSignal } from "~/services/httpAsyncStorage.server"; |
| 4 | +import { logger } from "~/services/logger.server"; |
| 5 | + |
| 6 | +// Same-origin reverse proxy for PostHog. posthog-js sets `api_host: "/ph"`, so |
| 7 | +// analytics is served first-party and forwarded to PostHog Cloud server-side. |
| 8 | +// Asset requests (recorder script, array bundles) go to the assets host and |
| 9 | +// everything else (ingest, feature flags, session recording) to the ingest |
| 10 | +// host, as PostHog's reverse-proxy docs require. Streaming and header handling |
| 11 | +// mirror the Electric proxy in longPollingFetch.ts. |
| 12 | + |
| 13 | +const PH_PREFIX = "/ph"; |
| 14 | + |
| 15 | +function isAssetPath(upstreamPath: string): boolean { |
| 16 | + return upstreamPath.startsWith("/static/") || upstreamPath.startsWith("/array/"); |
| 17 | +} |
| 18 | + |
| 19 | +async function proxyToPostHog(request: Request): Promise<Response> { |
| 20 | + const url = new URL(request.url); |
| 21 | + |
| 22 | + const upstreamPath = url.pathname.slice(PH_PREFIX.length) || "/"; |
| 23 | + const hostname = isAssetPath(upstreamPath) ? env.POSTHOG_ASSETS_HOST : env.POSTHOG_INGEST_HOST; |
| 24 | + const upstreamUrl = `https://${hostname}${upstreamPath}${url.search}`; |
| 25 | + |
| 26 | + const headers = new Headers(request.headers); |
| 27 | + // PostHog routes on Host, so point it at the upstream. accept-encoding is |
| 28 | + // dropped so we don't get a compressed body we'd have to re-describe. |
| 29 | + headers.set("host", hostname); |
| 30 | + headers.delete("accept-encoding"); |
| 31 | + |
| 32 | + // /ph is same-origin, so the browser sends every first-party cookie. Forward |
| 33 | + // only PostHog's own so we never leak the app session cookie to a third party. |
| 34 | + const cookie = headers.get("cookie"); |
| 35 | + if (cookie) { |
| 36 | + const forwarded = cookie |
| 37 | + .split(";") |
| 38 | + .filter((c) => { |
| 39 | + const name = c.trimStart().split("=", 1)[0]; |
| 40 | + return name.startsWith("ph_") || name.startsWith("__ph"); |
| 41 | + }) |
| 42 | + .join(";"); |
| 43 | + |
| 44 | + if (forwarded) { |
| 45 | + headers.set("cookie", forwarded); |
| 46 | + } else { |
| 47 | + headers.delete("cookie"); |
| 48 | + } |
| 49 | + } |
| 50 | + |
| 51 | + const hasBody = request.method !== "GET" && request.method !== "HEAD"; |
| 52 | + |
| 53 | + // `duplex` isn't in the DOM RequestInit lib types but undici needs it to |
| 54 | + // stream a request body; widen the type rather than suppress. |
| 55 | + const init: RequestInit & { duplex?: "half" } = { |
| 56 | + method: request.method, |
| 57 | + headers, |
| 58 | + body: hasBody ? request.body : undefined, |
| 59 | + signal: getRequestAbortSignal(), |
| 60 | + duplex: hasBody ? "half" : undefined, |
| 61 | + }; |
| 62 | + |
| 63 | + let upstream: Response | undefined; |
| 64 | + try { |
| 65 | + upstream = await fetch(upstreamUrl, init); |
| 66 | + |
| 67 | + // Strip encoding headers that can misdescribe the proxied body (see longPollingFetch). |
| 68 | + const responseHeaders = new Headers(upstream.headers); |
| 69 | + responseHeaders.delete("content-encoding"); |
| 70 | + responseHeaders.delete("content-length"); |
| 71 | + |
| 72 | + return new Response(upstream.body, { |
| 73 | + status: upstream.status, |
| 74 | + statusText: upstream.statusText, |
| 75 | + headers: responseHeaders, |
| 76 | + }); |
| 77 | + } catch (error) { |
| 78 | + try { |
| 79 | + await upstream?.body?.cancel(); |
| 80 | + } catch {} |
| 81 | + |
| 82 | + if (error instanceof Error && error.name === "AbortError") { |
| 83 | + throw new Response(null, { status: 499 }); |
| 84 | + } |
| 85 | + |
| 86 | + logger.error("[posthog-proxy] fetch error", { |
| 87 | + error: error instanceof Error ? error.message : String(error), |
| 88 | + }); |
| 89 | + throw new Response("PostHog proxy error", { status: 502 }); |
| 90 | + } |
| 91 | +} |
| 92 | + |
| 93 | +export async function loader({ request }: LoaderFunctionArgs) { |
| 94 | + return proxyToPostHog(request); |
| 95 | +} |
| 96 | + |
| 97 | +export async function action({ request }: ActionFunctionArgs) { |
| 98 | + return proxyToPostHog(request); |
| 99 | +} |
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