Langfuse Production Checklist

// config/langfuse.prod.ts
import { Langfuse } from "langfuse";

function validateConfig(config: Record<string, any>): void {
  const required = ["publicKey", "secretKey"];
  const missing = required.filter((key) => !config[key]);

  if (missing.length > 0) {
    throw new Error(`Missing Langfuse config: ${missing.join(", ")}`);
  }

  // Verify production keys (not dev/test)
  if (config.publicKey.includes("test") || config.publicKey.includes("dev")) {
    console.warn("WARNING: Using non-production API keys!");
  }
}

export function createProductionLangfuse() {
  const config = {
    publicKey: process.env.LANGFUSE_PUBLIC_KEY!,
    secretKey: process.env.LANGFUSE_SECRET_KEY!,
    baseUrl: process.env.LANGFUSE_HOST || "https://cloud.langfuse.com",
    // Production settings
    flushAt: 25,
    flushInterval: 5000,
    requestTimeout: 15000,
    enabled: process.env.NODE_ENV === "production",
  };

  validateConfig(config);

  return new Langfuse(config);
}

// lib/langfuse-production.ts
import { Langfuse } from "langfuse";

let langfuseInstance: Langfuse | null = null;

export function getLangfuse(): Langfuse {
  if (!langfuseInstance) {
    langfuseInstance = createProductionLangfuse();

    // Register graceful shutdown
    const shutdown = async () => {
      console.log("Flushing Langfuse traces...");
      await langfuseInstance?.shutdownAsync();
      console.log("Langfuse shutdown complete");
    };

    process.on("SIGTERM", shutdown);
    process.on("SIGINT", shutdown);
    process.on("beforeExit", shutdown);
  }

  return langfuseInstance;
}

// Production-safe trace wrapper
export async function safeTrace<T>(
  name: string,
  operation: (trace: ReturnType<typeof langfuse.trace>) => Promise<T>,
  metadata?: Record<string, any>
): Promise<T> {
  const langfuse = getLangfuse();

  let trace;
  try {
    trace = langfuse.trace({
      name,
      metadata: {
        ...metadata,
        environment: "production",
      },
    });
  } catch (error) {
    console.error("Failed to create Langfuse trace:", error);
    // Continue without tracing - don't fail the operation
    return operation(null as any);
  }

  try {
    const result = await operation(trace);
    trace.update({ output: { success: true } });
    return result;
  } catch (error) {
    trace.update({
      output: { error: String(error) },
      level: "ERROR",
    });
    throw error;
  }
}

// scripts/verify-langfuse-prod.ts
import { Langfuse } from "langfuse";

async function verifyProduction() {
  console.log("=== Langfuse Production Verification ===\n");

  const checks: Array<{ name: string; check: () => Promise<boolean> }> = [
    {
      name: "Environment variables set",
      check: async () => {
        const required = [
          "LANGFUSE_PUBLIC_KEY",
          "LANGFUSE_SECRET_KEY",
        ];
        const missing = required.filter((key) => !process.env[key]);
        if (missing.length > 0) {
          console.log(`  Missing: ${missing.join(", ")}`);
          return false;
        }
        return true;
      },
    },
    {
      name: "API keys are production keys",
      check: async () => {
        const key = process.env.LANGFUSE_PUBLIC_KEY || "";
        const isProduction =
          !key.includes("test") &&
          !key.includes("dev") &&
          key.startsWith("pk-lf-");
        if (!isProduction) {
          console.log("  Key appears to be non-production");
        }
        return isProduction;
      },
    },
    {
      name: "Can create trace",
      check: async () => {
        const langfuse = new Langfuse();
        const trace = langfuse.trace({
          name: "production-verification",
          metadata: { test: true },
        });
        await langfuse.flushAsync();
        return true;
      },
    },
    {
      name: "Graceful shutdown works",
      check: async () => {
        const langfuse = new Langfuse();
        langfuse.trace({ name: "shutdown-test" });
        await langfuse.shutdownAsync();
        return true;
      },
    },
  ];

  let passed = 0;
  let failed = 0;

  for (const { name, check } of checks) {
    process.stdout.write(`[ ] ${name}...`);
    try {
      const result = await check();
      if (result) {
        console.log("\r[✓]");
        passed++;
      } else {
        console.log("\r[✗]");
        failed++;
      }
    } catch (error) {
      console.log(`\r[✗] Error: ${error}`);
      failed++;
    }
  }

  console.log(`\n=== Results: ${passed} passed, ${failed} failed ===`);

  if (failed > 0) {
    process.exit(1);
  }
}

verifyProduction();

// Monitor Langfuse health in production
interface LangfuseMetrics {
  tracesCreated: number;
  tracesFailed: number;
  flushLatencyMs: number[];
  lastFlushTime: Date | null;
}

const metrics: LangfuseMetrics = {
  tracesCreated: 0,
  tracesFailed: 0,
  flushLatencyMs: [],
  lastFlushTime: null,
};

// Expose metrics endpoint
app.get("/metrics/langfuse", (req, res) => {
  const avgFlushLatency =
    metrics.flushLatencyMs.length > 0
      ? metrics.flushLatencyMs.reduce((a, b) => a + b) /
        metrics.flushLatencyMs.length
      : 0;

  res.json({
    tracesCreated: metrics.tracesCreated,
    tracesFailed: metrics.tracesFailed,
    avgFlushLatencyMs: avgFlushLatency.toFixed(2),
    lastFlushTime: metrics.lastFlushTime?.toISOString(),
    errorRate: (
      (metrics.tracesFailed / (metrics.tracesCreated || 1)) *
      100
    ).toFixed(2),
  });
});

// Final production Langfuse configuration
export const productionLangfuseConfig = {
  // Authentication
  publicKey: process.env.LANGFUSE_PUBLIC_KEY!,
  secretKey: process.env.LANGFUSE_SECRET_KEY!,
  baseUrl: process.env.LANGFUSE_HOST || "https://cloud.langfuse.com",

  // Batching (optimized for production)
  flushAt: 25,          // Batch 25 events
  flushInterval: 5000,  // Flush every 5 seconds

  // Timeouts
  requestTimeout: 15000, // 15 second timeout

  // Enable/disable
  enabled: process.env.NODE_ENV === "production",

  // Debug (disabled in production)
  debug: false,
};