Express Adapter Configuration

The lens function accepts a single configuration object that controls how Lens integrates with your Express application. This guide provides a clear reference and practical examples to help you set it up quickly.

Example: Prisma Query Watcher

Here’s how to enable query watching specifically for Prisma in your Express application:

import { lens } from "@lensjs/express";
import { createPrismaHandler } from "@lensjs/watchers";
import { PrismaClient } from "@prisma/client";
import express from "express";

const app = express();
const prisma = new PrismaClient({ log: ["query"] });

await lens({
  app,
  path: "/lens", // The Lens dashboard will be available at http://localhost:3000/lens
  appName: "My Express App",
  queryWatcher: {
    enabled: true, // Enable query watching
    handler: createPrismaHandler({
      prisma,
      provider: "mysql"
    }),
  },
});

Complete Example: Full Configuration Options

This snippet illustrates all available configuration options for the Express adapter, along with inline comments for clarity:

import express, { Request } from "express";
import { lens } from "@lensjs/express";
import { createPrismaHandler } from "@lensjs/watchers";
import { PrismaClient } from "@prisma/client";

const app = express();
const prisma = new PrismaClient({ log: ["query"] });

await lens({
  // Required: Your Express application instance.
  app,

  // Optional: Configuration for the query watcher.
  queryWatcher: {
    enabled: true, // Set to true to enable query watching.
    handler: createPrismaHandler({
      prisma,
      provider: "mysql", // Specify your database provider (e.g., "mysql", "postgresql").
    }),
  },

  // Optional: Enable or disable the request watcher. Defaults to `true`.
  requestWatcherEnabled: true,

  // Optional: Enable or disable the exception watcher. defaults to `true`.
  exceptionWatcherEnabled: true,

  // Optional: Enable or disable the cache watcher. Defaults to `false`.
  cacheWatcherEnabled: true,

  // Optional: The URL path where the Lens dashboard will be accessible. Defaults to "/lens".
  path: "/lens",

  // Optional: The display name for your application in the Lens dashboard. Defaults to "Lens".
  appName: "My Express App",

  // Optional: An array of regex patterns for routes that Lens should ignore.
  ignoredPaths: [/^\/health/, /^\/metrics/],

  // Optional: An array of regex patterns to exclusively watch. If provided, only routes matching these patterns will be monitored.
  onlyPaths: [/^\/api/],

  // Optional: An asynchronous function to determine if current request is authenticated.
  isAuthenticated: async (req: Request) => {
    const jwtToken = req.headers["authorization"]?.split(" ")[1];
    const jwtSecret = "secret";
    // Replace with your actual JWT validation logic
    return jwtToken === getValidJwtToken(jwtToken, jwtSecret);
  },

  // Optional: An asynchronous function to resolve and attach user information to Lens events/logs.
  getUser: async (req: Request) => {
    // Replace with your actual user retrieval logic
    return {
      id: "123",
      name: "Jane Doe",
      email: "jane@example.com",
    };
  },

  /**
   * Optional: Configuration to hide sensitive request parameters or headers from being displayed in Lens.
   * This is useful for security and privacy, preventing sensitive data like passwords or authorization tokens
   * from appearing in the monitoring dashboard.
   */
  hiddenParams: {
    headers: [
      'Authorization',
      'Basic',
    ],
    bodyParams: [
      'password',
      'passwordConfirmation',
      'secret',
      'password_confirmation'
    ],
  },

  /**
   * Optional: Configuration for the queued store, which buffers data before writing to the database.
   * This helps optimize performance by reducing the frequency of direct database write operations.
   */
  storeQueueConfig: {
    batchSize: 100, // The number of entries to process in a single batch.
    processIntervalMs: 2_000, // The interval (in milliseconds) at which the queue is processed.
    warnThreshold: 100_000, // A warning will be logged if the queue size exceeds this threshold.
  },
});