Scout logs internal activity via a configured logging function with the signature (msg: string, level: LogLevel) => void.

Express middleware logging

To enable agent logging with the express middleware, your middleware should be set up like the following:

const scout = require("@scout_apm/scout-apm");
const express = require("express");

// The "main" function of your application
async function start() {
  // Create your express application
  const app = express();

  // Install scout
  await scout.install(
    // Configuration for the scout agent
      allowShutdown: true, // allow shutting down spawned scout-agent processes from this program
      monitor: true, // enable monitoring
      name: "<application name>",
      key: "<scout key>",
    // Additional scout options
      logFn: scout.consoleLogFn,

  // Enable the app-wide scout middleware

  // ... Add other middleware/handlers ...


If you are using winston you may build a logFn by passing a winston.Logger to the exported scout.buildWinstonLogger helper function:

  logFn: scout.buildWinstonLogger(yourLogger),

If a winston.Logger instance is provided, Scout’s logging defaults to the same log level as the instance, otherwise it defaults to ERROR. You may set the logging to a stricter level to quiet the agent’s logging via the logLevel in the config sub-object (or SCOUT_LOG_LEVEL via ENV). The underlying LoggerInterface’s level will take precedence if it is tighter than the logLevel configuration.

Log Levels

The possible log levels are as follows: