walkeros-using-logger

Using the walkerOS Logger

Overview

The logger is walkerOS's standard logging system, available in all sources and destinations via env.logger or logger parameter. It provides scoped, level-aware logging that replaces console.log.

Core principle: Don't log what the collector already logs. Only log meaningful operations like external API calls, transformations, and validation errors.

Logger Access

In Sources

export const sourceFetch = async (
  config: PartialConfig,
  env: Types['env'], // env.logger is available here
): Promise<FetchSource> => {
  // Logger is scoped automatically by collector: [type:sourceId]
  env.logger.info('Server listening on port 3000');
};

In Destinations

export const destinationDataManager: DestinationInterface = {
  async init({ config, env, logger }) {
    // logger parameter is scoped automatically: [datamanager]
    logger.debug('Auth client created');
  },

  async push(event, { config, data, env, logger }) {
    // logger parameter is scoped: [datamanager]
    logger.debug('API response', { status: 200 });
  },
};

Note: You don't need to create or configure the logger—it's provided automatically with proper scoping.

Logger Methods

interface Logger.Instance {
  error(message: string | Error, context?: unknown | Error): void;
  warn(message: string | Error, context?: unknown | Error): void;
  info(message: string | Error, context?: unknown | Error): void;
  debug(message: string | Error, context?: unknown | Error): void;
  throw(message: string | Error, context?: unknown): never;
  json(data: unknown): void;
  scope(name: string): Logger.Instance;
}

Log Levels

• ERROR (0): Always visible—use for fatal/critical errors only
• WARN (1): Degraded state, config issues, transient failures
• INFO (2): High-level operations (server startup, event processed)
• DEBUG (3): Low-level details (API calls, transformations)

Default: ERROR only (must configure to see WARN/INFO/DEBUG)