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This example demonstrates how to build a Next.js application with OpenAI integration and OpenInference instrumentation.

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Prerequisites

  • Node.js 18+
  • OpenAI API key
  • Phoenix or another OpenTelemetry collector

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Installation

1

Create Next.js app

npx create-next-app@latest my-chat-app
cd my-chat-app
2

Install dependencies

npm install openai \
  @arizeai/openinference-instrumentation-openai \
  @opentelemetry/sdk-trace-node \
  @opentelemetry/exporter-trace-otlp-proto
3

Set environment variables

Create a .env.local file:
OPENAI_API_KEY="your-api-key"
COLLECTOR_ENDPOINT="http://localhost:6006/v1/traces"

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Instrumentation Setup

Next.js requires a specific instrumentation pattern using the instrumentation hook.

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Create Root Instrumentation File

Create instrumentation.ts in the root directory: 
export async function register() {
  if (process.env.NEXT_RUNTIME === "nodejs") {
    await import("./instrumentation-node");
  }
}

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Create Node.js Instrumentation

Create instrumentation-node.ts: 
import { SimpleSpanProcessor } from "@opentelemetry/sdk-trace-base";
import { OTLPTraceExporter } from "@opentelemetry/exporter-trace-otlp-proto";
import { OpenAIInstrumentation } from "@arizeai/openinference-instrumentation-openai";
import * as OpenAI from "openai";
import { diag, DiagConsoleLogger, DiagLogLevel } from "@opentelemetry/api";
import { registerInstrumentations } from "@opentelemetry/instrumentation";
import { NodeTracerProvider } from "@opentelemetry/sdk-trace-node";
import { Resource } from "@opentelemetry/resources";

// For troubleshooting, set the log level to DiagLogLevel.DEBUG
diag.setLogger(new DiagConsoleLogger(), DiagLogLevel.INFO);

const provider = new NodeTracerProvider({
  resource: new Resource({
    ["openinference.project.name"]: "nextjs-chat",
  }),
});

provider.addSpanProcessor(
  new SimpleSpanProcessor(
    new OTLPTraceExporter({
      url: process.env.COLLECTOR_ENDPOINT || "http://localhost:6006/v1/traces",
    }),
  ),
);

// OpenAI must be manually instrumented as it doesn't have a traditional module structure
const openAIInstrumentation = new OpenAIInstrumentation({});
openAIInstrumentation.manuallyInstrument(OpenAI);

registerInstrumentations({
  instrumentations: [openAIInstrumentation],
});

provider.register();

diag.info("👀 OpenInference initialized");

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Enable Instrumentation in Next.js Config

Update next.config.js: 
/** @type {import('next').NextConfig} */
const nextConfig = {
  // Enable experimental instrumentation
  experimental: {
    instrumentationHook: true,
  },
};

module.exports = nextConfig;

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API Route

Create app/api/chat/route.ts: 
import { NextRequest, NextResponse } from "next/server";
import OpenAI from "openai";

const openai = new OpenAI({
  apiKey: process.env.OPENAI_API_KEY,
});

export async function POST(request: NextRequest) {
  try {
    const { messages } = await request.json();

    if (!messages || !Array.isArray(messages)) {
      return NextResponse.json(
        { error: "Messages array is required" },
        { status: 400 }
      );
    }

    const response = await openai.chat.completions.create({
      model: "gpt-3.5-turbo",
      messages: messages,
      temperature: 0.7,
      max_tokens: 500,
    });

    return NextResponse.json({
      message: response.choices[0].message,
    });
  } catch (error) {
    console.error("Error in chat API:", error);
    return NextResponse.json(
      { error: "Internal server error" },
      { status: 500 }
    );
  }
}

​
Streaming API Route

For streaming responses, create app/api/chat/stream/route.ts: 
import { NextRequest } from "next/server";
import OpenAI from "openai";

const openai = new OpenAI({
  apiKey: process.env.OPENAI_API_KEY,
});

export async function POST(request: NextRequest) {
  try {
    const { messages } = await request.json();

    const stream = await openai.chat.completions.create({
      model: "gpt-3.5-turbo",
      messages: messages,
      temperature: 0.7,
      max_tokens: 500,
      stream: true,
    });

    // Create a readable stream
    const encoder = new TextEncoder();
    const readable = new ReadableStream({
      async start(controller) {
        try {
          for await (const chunk of stream) {
            const content = chunk.choices[0]?.delta?.content || "";
            controller.enqueue(encoder.encode(content));
          }
          controller.close();
        } catch (error) {
          controller.error(error);
        }
      },
    });

    return new Response(readable, {
      headers: {
        "Content-Type": "text/plain; charset=utf-8",
      },
    });
  } catch (error) {
    console.error("Error in streaming chat API:", error);
    return new Response("Internal server error", { status: 500 });
  }
}

​
Chat UI Component

Create app/components/chat.tsx: 
"use client";

import { useState } from "react";

interface Message {
  role: "user" | "assistant";
  content: string;
}

export function Chat() {
  const [messages, setMessages] = useState<Message[]>([]);
  const [input, setInput] = useState("");
  const [loading, setLoading] = useState(false);

  const sendMessage = async () => {
    if (!input.trim()) return;

    const userMessage: Message = { role: "user", content: input };
    setMessages((prev) => [...prev, userMessage]);
    setInput("");
    setLoading(true);

    try {
      const response = await fetch("/api/chat", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({
          messages: [...messages, userMessage],
        }),
      });

      const data = await response.json();
      setMessages((prev) => [...prev, data.message]);
    } catch (error) {
      console.error("Error sending message:", error);
    } finally {
      setLoading(false);
    }
  };

  return (
    <div className="flex flex-col h-screen max-w-2xl mx-auto p-4">
      <div className="flex-1 overflow-y-auto space-y-4 mb-4">
        {messages.map((message, index) => (
          <div
            key={index}
            className={`p-4 rounded-lg ${
              message.role === "user"
                ? "bg-blue-100 ml-auto max-w-[80%]"
                : "bg-gray-100 mr-auto max-w-[80%]"
            }`}
          >
            <p className="text-sm font-semibold mb-1">
              {message.role === "user" ? "You" : "Assistant"}
            </p>
            <p>{message.content}</p>
          </div>
        ))}
        {loading && (
          <div className="bg-gray-100 p-4 rounded-lg mr-auto max-w-[80%]">
            <p className="text-sm font-semibold mb-1">Assistant</p>
            <p className="text-gray-500">Thinking...</p>
          </div>
        )}
      </div>
      <div className="flex gap-2">
        <input
          type="text"
          value={input}
          onChange={(e) => setInput(e.target.value)}
          onKeyPress={(e) => e.key === "Enter" && sendMessage()}
          placeholder="Type your message..."
          className="flex-1 p-2 border rounded"
          disabled={loading}
        />
        <button
          onClick={sendMessage}
          disabled={loading}
          className="px-4 py-2 bg-blue-500 text-white rounded hover:bg-blue-600 disabled:opacity-50"
        >
          Send
        </button>
      </div>
    </div>
  );
}

​
Main Page

Update app/page.tsx: 
import { Chat } from "./components/chat";

export default function Home() {
  return (
    <main>
      <h1 className="text-2xl font-bold text-center py-4">
        Next.js Chat with OpenInference
      </h1>
      <Chat />
    </main>
  );
}

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Run the Application

npm run dev
Visit http://localhost:3000 to use the chat interface.

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Key Features

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Automatic Instrumentation

Next.js instrumentation hook automatically initializes tracing before your application code runs.

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Server-Side Only

Instrumentation only runs in the Node.js runtime (server-side), not in the browser.

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API Routes

Both standard and streaming API routes are automatically traced.

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Next Steps

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