Next.js client-side instrumentation example

Author: petyosi

examples/nextjs-client-side-instrumentation/.gitignore

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+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.*
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/versions
+
+# testing
+/coverage
+
+# next.js
+/.next/
+/out/
+
+# production
+/build
+
+# misc
+.DS_Store
+*.pem
+
+# debug
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+.pnpm-debug.log*
+
+# env files (can opt-in for committing if needed)
+.env*
+
+# vercel
+.vercel
+
+# typescript
+*.tsbuildinfo
+next-env.d.ts

examples/nextjs-client-side-instrumentation/README.md

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+# Example for a Next.js client/server distributed OTel instrumentation with Logfire
+
+
+The example showcases how a fetch request initiated from the browser can propagate to the server and then to a third-party service, all while being instrumented with OpenTelemetry. The example uses the Logfire OTel SDK for both the client and server sides.
+
+## Highlights
+
+- The `ClientInstrumentationProvider` is a client-only component that instruments the browser fetch.
+- To avoid exposing the write token, the middleware.ts proxies the logfire `/v1/traces` request.
+- The instrumentation.ts file is the standard `@vercel/otel` setup. 
+- The `.env` should look like this: 
+
+```sh
+OTEL_EXPORTER_OTLP_TRACES_ENDPOINT=https://logfire-api.pydantic.dev/v1/traces
+OTEL_EXPORTER_OTLP_METRICS_ENDPOINT=https://logfire-api.pydantic.dev/v1/metrics
+OTEL_EXPORTER_OTLP_HEADERS='Authorization=your-token'
+LOGFIRE_TOKEN='your-token'
+```
+
+NOTE: alternatively, if you're not sure about the connection between the client and the server, you can host the proxy at a different location (e.g. Cloudflare).

examples/nextjs-client-side-instrumentation/app/api/hello/route.ts

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+import * as logfire from "@pydantic/logfire-api";
+
+export async function GET() {
+  logfire.info("server span");
+  return Response.json({ message: "Hello World!" });
+}
+

examples/nextjs-client-side-instrumentation/app/components/ClientInstrumentationProvider.tsx

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+import { ZoneContextManager } from "@opentelemetry/context-zone";
+import { OTLPTraceExporter } from "@opentelemetry/exporter-trace-otlp-http";
+import { registerInstrumentations } from "@opentelemetry/instrumentation";
+import { FetchInstrumentation } from "@opentelemetry/instrumentation-fetch";
+import { Resource } from "@opentelemetry/resources";
+import {
+  RandomIdGenerator,
+  SimpleSpanProcessor,
+  WebTracerProvider,
+} from "@opentelemetry/sdk-trace-web";
+import {
+  ATTR_SERVICE_NAME,
+  ATTR_SERVICE_VERSION,
+} from "@opentelemetry/semantic-conventions";
+import { ReactNode, useEffect } from "react";
+
+// JS port of https://github.com/pydantic/logfire/blob/main/logfire/_internal/ulid.py without the parameters
+function ulid(): bigint {
+  // Timestamp: first 6 bytes of the ULID (48 bits)
+  // Note that it's not important that this timestamp is super precise or unique.
+  // It just needs to be roughly monotonically increasing so that the ULID is sortable, at least for our purposes.
+  let result = BigInt(Date.now());
+
+  // Randomness: next 10 bytes of the ULID (80 bits)
+  const randomness = crypto.getRandomValues(new Uint8Array(10));
+  for (const segment of randomness) {
+    result <<= BigInt(8);
+    result |= BigInt(segment);
+  }
+
+  return result;
+}
+
+class ULIDGenerator extends RandomIdGenerator {
+  override generateTraceId = () => {
+    return ulid().toString(16).padStart(32, "0");
+  };
+}
+
+export default function ClientInstrumentationProvider(
+  { children }: { children: ReactNode },
+) {
+  useEffect(() => {
+    const url = new URL(window.location.href);
+    url.pathname = "/client-traces";
+    const resource = new Resource({
+      [ATTR_SERVICE_NAME]: "logfire-frontend",
+      [ATTR_SERVICE_VERSION]: "0.0.1",
+    });
+
+    const provider = new WebTracerProvider({
+      resource,
+      idGenerator: new ULIDGenerator(),
+      spanProcessors: [
+        new SimpleSpanProcessor(
+          new OTLPTraceExporter({ url: url.toString() }),
+        ),
+      ],
+    });
+
+    provider.register({
+      contextManager: new ZoneContextManager(),
+    });
+
+    registerInstrumentations({
+      instrumentations: [new FetchInstrumentation()],
+    });
+  }, []);
+  return children;
+}

examples/nextjs-client-side-instrumentation/app/components/HelloButton.tsx

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+"use client";
+import { useState } from "react";
+
+export default function HelloButton() {
+  const [message, setMessage] = useState("");
+  const [loading, setLoading] = useState(false);
+
+  const fetchHello = async () => {
+    setLoading(true);
+    try {
+      const response = await fetch("/api/hello");
+      const data = await response.json();
+      setMessage(data.message);
+    } catch {
+      setMessage("Error fetching data");
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  return (
+    <div>
+      <button
+        onClick={fetchHello}
+        disabled={loading}
+      >
+        {loading ? "Loading..." : "Fetch Hello World"}
+      </button>
+      {message && <p>{message}</p>}
+    </div>
+  );
+}
+

examples/nextjs-client-side-instrumentation/app/favicon.ico

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+:root {
+  --background: #ffffff;
+  --foreground: #171717;
+}
+
+@media (prefers-color-scheme: dark) {
+  :root {
+    --background: #0a0a0a;
+    --foreground: #ededed;
+  }
+}
+
+html,
+body {
+  max-width: 100vw;
+  overflow-x: hidden;
+}
+
+body {
+  color: var(--foreground);
+  background: var(--background);
+  font-family: Arial, Helvetica, sans-serif;
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+}
+
+* {
+  box-sizing: border-box;
+  padding: 0;
+  margin: 0;
+}
+
+a {
+  color: inherit;
+  text-decoration: none;
+}
+
+@media (prefers-color-scheme: dark) {
+  html {
+    color-scheme: dark;
+  }
+}

examples/nextjs-client-side-instrumentation/app/globals.css

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+import type { Metadata } from "next";
+import { Geist, Geist_Mono } from "next/font/google";
+import "./globals.css";
+
+const geistSans = Geist({
+  variable: "--font-geist-sans",
+  subsets: ["latin"],
+});
+
+const geistMono = Geist_Mono({
+  variable: "--font-geist-mono",
+  subsets: ["latin"],
+});
+
+export const metadata: Metadata = {
+  title: "Create Next App",
+  description: "Generated by create next app",
+};
+
+export default function RootLayout({
+  children,
+}: Readonly<{
+  children: React.ReactNode;
+}>) {
+  return (
+    <html lang="en">
+      <body className={`${geistSans.variable} ${geistMono.variable}`}>
+        {children}
+      </body>
+    </html>
+  );
+}