leshan-mcp-server/src/utils/loggerConfig.js

A standards-compliant MCP server for Leshan LwM2M, exposing Leshan as Model Context Protocol tools.

import { createWriteStream } from "fs";
import { mkdir } from "fs/promises";
import { join, dirname } from "path";
import { fileURLToPath } from "url";
import { env } from "../config/env.js";

const __dirname = dirname(fileURLToPath(import.meta.url));
const LOG_DIR = join(__dirname, "../../logs");

class Logger {
  constructor() {
    this.logLevel = env.LOG_LEVEL;
    this.enableFileLogging = env.ENABLE_FILE_LOGGING;
    this.logStream = null;
    this.levels = { debug: 0, info: 1, warn: 2, error: 3 };
    this.initialized = false;
  }

  async init() {
    if (this.initialized) return;
    
    if (this.enableFileLogging) {
      try {
        await mkdir(LOG_DIR, { recursive: true });
        this.logStream = createWriteStream(
          join(LOG_DIR, `mcp-server-${new Date().toISOString().split('T')[0]}.log`),
          { flags: 'a' }
        );
      } catch (error) {
        console.error("Failed to initialize file logging:", error.message);
      }
    }
    this.initialized = true;
  }

  shouldLog(level) {
    return this.levels[level] >= this.levels[this.logLevel];
  }

  formatMessage(level, message, meta = {}) {
    const timestamp = new Date().toISOString();
    const logEntry = {
      timestamp,
      level: level.toUpperCase(),
      message,
      pid: process.pid,
      ...meta
    };
    return JSON.stringify(logEntry);
  }

  log(level, message, meta = {}) {
    if (!this.shouldLog(level)) return;

    const formattedMessage = this.formatMessage(level, message, meta);
    
    // Always log to stderr (MCP protocol uses stdout)
    console.error(formattedMessage);
    
    // Log to file if enabled
    if (this.logStream) {
      this.logStream.write(formattedMessage + '\n');
    }
  }

  debug(message, meta) { this.log('debug', message, meta); }
  info(message, meta) { this.log('info', message, meta); }
  warn(message, meta) { this.log('warn', message, meta); }
  error(message, meta) { this.log('error', message, meta); }

  // Graceful shutdown
  async close() {
    if (this.logStream) {
      return new Promise((resolve) => {
        this.logStream.end(resolve);
      });
    }
  }
}

const logger = new Logger();

export function configureLogger() {
  return logger.init();
}

export default logger;