Langfuse Prod Checklist

// v4+ Production Config
import { LangfuseSpanProcessor } from "@langfuse/otel";
import { NodeSDK } from "@opentelemetry/sdk-node";

const processor = new LangfuseSpanProcessor({
  exportIntervalMillis: 5000,  // Flush every 5s
  maxExportBatchSize: 50,      // Batch size
  maxQueueSize: 2048,          // Buffer limit
});

const sdk = new NodeSDK({ spanProcessors: [processor] });
sdk.start();

// Graceful shutdown on all signals
for (const signal of ["SIGTERM", "SIGINT", "SIGUSR2"]) {
  process.on(signal, async () => {
    await sdk.shutdown();
    process.exit(0);
  });
}

// v3 Legacy Production Config
import { Langfuse } from "langfuse";

const langfuse = new Langfuse({
  flushAt: 25,            // Balance between latency and efficiency
  flushInterval: 5000,    // 5 second flush interval
  requestTimeout: 15000,  // 15s timeout
  enabled: true,          // Explicitly enable
});

process.on("beforeExit", () => langfuse.shutdownAsync());
process.on("SIGTERM", () => langfuse.shutdownAsync().then(() => process.exit(0)));

import { observe, updateActiveObservation, startActiveObservation } from "@langfuse/tracing";

// Wrap all traced operations with error safety
const tracedEndpoint = observe({ name: "api-endpoint" }, async (req: Request) => {
  try {
    updateActiveObservation({
      input: { path: req.url, method: req.method },
      metadata: { userId: req.userId },
    });

    const result = await processRequest(req);

    updateActiveObservation({ output: { status: 200 } });
    return result;
  } catch (error) {
    // Log error to trace -- don't let tracing error mask app error
    try {
      updateActiveObservation({
        output: { error: String(error) },
        metadata: { level: "ERROR" },
      });
    } catch {
      // Tracing failure must never break the app
    }
    throw error;
  }
});

// scripts/verify-langfuse-prod.ts
import { LangfuseClient } from "@langfuse/client";
import { startActiveObservation, updateActiveObservation } from "@langfuse/tracing";

async function verify() {
  const checks: Array<{ name: string; pass: boolean; detail: string }> = [];

  // 1. Environment variables
  const requiredVars = ["LANGFUSE_PUBLIC_KEY", "LANGFUSE_SECRET_KEY"];
  for (const v of requiredVars) {
    checks.push({
      name: `Env: ${v}`,
      pass: !!process.env[v],
      detail: process.env[v] ? `SET (${process.env[v]!.slice(0, 10)}...)` : "MISSING",
    });
  }

  // 2. Key validation
  const pk = process.env.LANGFUSE_PUBLIC_KEY || "";
  const sk = process.env.LANGFUSE_SECRET_KEY || "";
  checks.push({
    name: "Key format",
    pass: pk.startsWith("pk-lf-") && sk.startsWith("sk-lf-"),
    detail: `Public: ${pk.startsWith("pk-lf-")}, Secret: ${sk.startsWith("sk-lf-")}`,
  });

  // 3. API connectivity
  try {
    const langfuse = new LangfuseClient();
    // Try fetching prompts as a connectivity test
    await langfuse.prompt.get("__health-check__").catch(() => {});
    checks.push({ name: "API connectivity", pass: true, detail: "Connected" });
  } catch (error) {
    checks.push({ name: "API connectivity", pass: false, detail: String(error) });
  }

  // 4. Trace creation
  try {
    await startActiveObservation("prod-verify", async () => {
      updateActiveObservation({
        input: { test: true },
        output: { verified: true },
        metadata: { verification: "pre-deploy" },
      });
    });
    checks.push({ name: "Trace creation", pass: true, detail: "Trace created" });
  } catch (error) {
    checks.push({ name: "Trace creation", pass: false, detail: String(error) });
  }

  // Report
  console.log("\n=== Langfuse Production Verification ===\n");
  let allPassed = true;
  for (const check of checks) {
    const icon = check.pass ? "PASS" : "FAIL";
    console.log(`  [${icon}] ${check.name}: ${check.detail}`);
    if (!check.pass) allPassed = false;
  }

  console.log(`\n${allPassed ? "All checks passed." : "SOME CHECKS FAILED."}\n`);
  if (!allPassed) process.exit(1);
}

verify();