♻️ Add abstractions for tracking server-side events (#1143)

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

apps/web/package.json

@@ -36,6 +36,7 @@
     "@trpc/client": "^10.13.0",
     "@trpc/next": "^10.13.0",
     "@trpc/react-query": "^10.13.0",
+    "@vercel/functions": "^1.0.2",
     "accept-language-parser": "^1.5.0",
     "autoprefixer": "^10.4.13",
     "class-variance-authority": "^0.7.0",

apps/web/src/app/posthog.ts

@@ -1,6 +1,7 @@
+import { waitUntil } from "@vercel/functions";
 import { PostHog } from "posthog-node";
 
-export function PostHogClient() {
+function PostHogClient() {
   if (!process.env.NEXT_PUBLIC_POSTHOG_API_KEY) return null;
 
   const posthogClient = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_API_KEY, {
@@ -10,3 +11,13 @@ export function PostHogClient() {
   });
   return posthogClient;
 }
+
+export const posthog = PostHogClient();
+
+export function posthogApiHandler() {
+  try {
+    waitUntil(Promise.all([posthog?.shutdownAsync()]));
+  } catch (error) {
+    console.error("Failed to flush PostHog events:", error);
+  }
+}

apps/web/src/pages/api/auth/[...nextauth].ts

@@ -1,11 +1,14 @@
 import type { NextApiRequest, NextApiResponse } from "next";
 
+import { posthogApiHandler } from "@/app/posthog";
 import { AuthApiRoute } from "@/utils/auth";
+import { composeApiHandlers } from "@/utils/next";
 
 export default async function auth(req: NextApiRequest, res: NextApiResponse) {
   if (req.method === "HEAD") {
-    return res.status(200).end();
+    res.status(200).end();
+    res.setHeader('Content-Length', '0');
+  } else {
+    return composeApiHandlers(AuthApiRoute, posthogApiHandler)(req, res);
   }
-
-  return AuthApiRoute(req, res);
 }

apps/web/src/pages/api/trpc/[trpc].ts

@@ -3,10 +3,12 @@ import { AppRouter, appRouter } from "@rallly/backend/trpc/routers";
 import * as Sentry from "@sentry/nextjs";
 import { createNextApiHandler } from "@trpc/server/adapters/next";
 
+import { posthog, posthogApiHandler } from "@/app/posthog";
 import { absoluteUrl, shortUrl } from "@/utils/absolute-url";
 import { getServerSession, isEmailBlocked } from "@/utils/auth";
 import { isSelfHosted } from "@/utils/constants";
 import { emailClient } from "@/utils/emails";
+import { composeApiHandlers } from "@/utils/next";
 
 export const config = {
   api: {
@@ -14,10 +16,10 @@ export const config = {
   },
 };
 
-export default createNextApiHandler<AppRouter>({
+const trpcApiHandler = createNextApiHandler<AppRouter>({
   router: appRouter,
   createContext: async (opts) => {
-    return createTRPCContext(opts, {
+    const res = createTRPCContext(opts, {
       async getUser({ req, res }) {
         const session = await getServerSession(req, res);
 
@@ -30,12 +32,15 @@ export default createNextApiHandler<AppRouter>({
           isGuest: session.user.email === null,
         };
       },
+      posthogClient: posthog || undefined,
       emailClient,
       isSelfHosted,
       isEmailBlocked,
       absoluteUrl,
       shortUrl,
     });
+
+    return res;
   },
   onError({ error }) {
     if (error.code === "INTERNAL_SERVER_ERROR") {
@@ -43,3 +48,5 @@ export default createNextApiHandler<AppRouter>({
     }
   },
 });
+
+export default composeApiHandlers(trpcApiHandler, posthogApiHandler);

apps/web/src/utils/auth.ts

@@ -17,7 +17,7 @@ import EmailProvider from "next-auth/providers/email";
 import GoogleProvider from "next-auth/providers/google";
 import { Provider } from "next-auth/providers/index";
 
-import { PostHogClient } from "@/app/posthog";
+import { posthog } from "@/app/posthog";
 import { absoluteUrl } from "@/utils/absolute-url";
 import { CustomPrismaAdapter } from "@/utils/auth/custom-prisma-adapter";
 import { mergeGuestsIntoUser } from "@/utils/auth/merge-user";
@@ -176,7 +176,6 @@ const getAuthOptions = (...args: GetServerSessionParams) =>
     },
     callbacks: {
       async signIn({ user, email, account, profile }) {
-        const posthog = PostHogClient();
         const distinctId = user.email ?? user.id;
         // prevent sign in if email is not verified
         if (
@@ -191,7 +190,6 @@ const getAuthOptions = (...args: GetServerSessionParams) =>
               reason: "email not verified",
             },
           });
-          await posthog?.shutdownAsync();
           return false;
         }
         // Make sure email is allowed
@@ -224,6 +222,14 @@ const getAuthOptions = (...args: GetServerSessionParams) =>
             await mergeGuestsIntoUser(user.id, [session.user.id]);
           }
 
+          posthog?.identify({
+            distinctId,
+            properties: {
+              name: user.name,
+              email: user.email,
+            },
+          });
+
           posthog?.capture({
             distinctId,
             event: "login",
@@ -231,7 +237,6 @@ const getAuthOptions = (...args: GetServerSessionParams) =>
               method: account?.provider,
             },
           });
-          await posthog?.shutdownAsync();
         }
 
         return true;

apps/web/src/utils/next.ts

@@ -0,0 +1,12 @@
+import { NextApiHandler } from "next";
+
+export function composeApiHandlers(...fns: NextApiHandler[]): NextApiHandler {
+  return async (req, res) => {
+    for (const fn of fns) {
+      await fn(req, res);
+      if (res.writableEnded) {
+        return;
+      }
+    }
+  };
+}

packages/backend/package.json

@@ -12,7 +12,6 @@
     "@rallly/database": "*",
     "@rallly/emails": "*",
     "@rallly/utils": "*",
-    "@vercel/functions": "^1.0.2",
     "@trpc/server": "^10.13.0",
     "iron-session": "^6.3.1",
     "spacetime": "^7.4.7",

packages/backend/trpc/context.ts

@@ -1,6 +1,7 @@
 import { EmailClient } from "@rallly/emails";
 import { inferAsyncReturnType, TRPCError } from "@trpc/server";
 import { CreateNextContextOptions } from "@trpc/server/adapters/next";
+import type { PostHog } from "posthog-node";
 
 export type GetUserFn = (opts: CreateNextContextOptions) => Promise<{
   id: string;
@@ -12,6 +13,7 @@ export interface TRPCContextParams {
   emailClient: EmailClient;
   isSelfHosted: boolean;
   isEmailBlocked?: (email: string) => boolean;
+  posthogClient?: PostHog;
   /**
    * Takes a relative path and returns an absolute URL to the app
    * @param path

packages/backend/trpc/routers/polls.ts

@@ -626,6 +626,7 @@ export const polls = router({
         },
         select: {
           id: true,
+          createdAt: true,
           timeZone: true,
           title: true,
           location: true,
@@ -859,7 +860,23 @@ export const polls = router({
           });
         });
 
-        waitUntil(Promise.all([emailToHost, ...emailsToParticipants]));
+        ctx.posthogClient?.capture({
+          distinctId: ctx.user.id,
+          event: "finalize poll",
+          properties: {
+            number_of_participants: poll.participants.length,
+            number_of_attendees: attendees.length,
+            dayjs_since_created: dayjs().diff(poll.createdAt, "day"),
+          },
+        });
+
+        waitUntil(
+          Promise.all([
+            emailToHost,
+            ...emailsToParticipants,
+            ctx.posthogClient?.flushAsync(),
+          ]),
+        );
       }
     }),
   reopen: possiblyPublicProcedure