import winston from 'winston';
export enum LogLevel {
DEBUG = 'debug',
INFO = 'info',
WARN = 'warn',
ERROR = 'error',
}
export class Logger {
private logger: winston.Logger;
constructor(level: LogLevel = LogLevel.INFO) {
this.logger = winston.createLogger({
level,
format: winston.format.combine(
winston.format.timestamp(),
winston.format.errors({ stack: true }),
winston.format.json()
),
transports: [
// CRITICAL: Only use stderr for MCP servers (stdout is for JSON-RPC)
new winston.transports.Console({
stderrLevels: ['error', 'warn', 'info', 'debug'],
}),
],
});
}
debug(message: string, meta?: Record<string, unknown>): void {
this.logger.debug(message, meta);
}
info(message: string, meta?: Record<string, unknown>): void {
this.logger.info(message, meta);
}
warn(message: string, meta?: Record<string, unknown>): void {
this.logger.warn(message, meta);
}
error(message: string, error?: Error, meta?: Record<string, unknown>): void {
this.logger.error(message, { ...meta, error: error?.message, stack: error?.stack });
}
}
// Singleton instance
const logLevel = (process.env.LOG_LEVEL?.toLowerCase() as LogLevel) || LogLevel.INFO;
export const logger = new Logger(logLevel);
