Logging

Simloop includes a pluggable logging system for observability during simulation runs.

Log Levels

Level	Description
`debug`	Detailed tracing (event processing, scheduling)
`info`	General information (lifecycle transitions)
`warn`	Warnings (unhandled event types)
`error`	Errors
`silent`	No output

Set the minimum level via the logLevel configuration option:


const sim = new SimulationEngine<Events>({
  logLevel: 'info', // only info, warn, error are shown
});

Built-in Lifecycle Logging

The engine automatically logs lifecycle transitions and event processing at debug level:

Simulation start/stop/pause/resume
Event processing (type, time)
Warm-up threshold crossed

User Logging via `ctx.log()`

Inside handlers, use ctx.log() for application-level logging:


sim.on('customer:arrive', (event, ctx) => {
  ctx.log('debug', `Customer ${event.payload.customerId} arrived at t=${ctx.clock}`);
  ctx.log('info', 'Processing new arrival');
});

Custom Logger

By default, Simloop uses ConsoleLogger. You can provide a custom SimLogger implementation via the logger option to redirect output (files, structured logging, etc.):


import { SimulationEngine } from 'simloop';
import type { SimLogger, LogLevel } from 'simloop';
 
const myLogger: SimLogger = {
  log(level: LogLevel, message: string): void {
    // send to file, external service, etc.
  },
};
 
const sim = new SimulationEngine<Events>({
  logger: myLogger,
  logLevel: 'debug',
});

Hooks for Tracing

Lifecycle hooks provide additional observability:


sim.beforeEach((event, ctx) => {
  console.log(`[${ctx.clock.toFixed(2)}] Processing: ${event.type}`);
});
 
sim.afterEach((event, ctx) => {
  console.log(`[${ctx.clock.toFixed(2)}] Done: ${event.type}`);
});
 
sim.onEnd((ctx) => {
  console.log(`Simulation ended at t=${ctx.clock}`);
});