Express Middleware

The Astralog Express middleware intercepts standard Node.js HTTP events to track latencies and statuses. It leverages the background event loop, meaning your Express routes remain blazing fast.

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Installation

npm install astralog-express astralog-node

Setup

// app.ts
import express from "express";
import { Client } from "astralog-node";
import { astralogMiddleware } from "astralog-express";

const client = new Client({ apiKey: "ast_sk_live_xxxxxxxxxxxxx" });
const app = express();

// Mount the middleware before your routes
app.use(astralogMiddleware(client));

app.get("/checkout", (req, res) => {
  // Manual logging will continue to work perfectly in parallel
  client.info("User accessed checkout", { user_id: "usr_123" });
  
  res.json({ status: "success" });
});

How it works

The middleware attaches an event listener to the native res.on('finish') event. When your route sends the response to the user, Astralog calculates the exact latency_ms, captures the HTTP status_code, and automatically generates a distributed X-Request-Id header to track the lifecycle.

Because it uses the native Node.js event architecture, it introduces 0ms of blocking latency to your HTTP response times.