/**
* Logging module for MySQL MCP Server
* Provides structured logging with different log levels
* All logs are written to stderr to avoid interfering with stdio transport
*
* Requirements: 7.1, 7.4, 7.5
*/
/**
* Log levels in order of severity
*/
export enum LogLevel {
DEBUG = 'debug',
INFO = 'info',
WARN = 'warn',
ERROR = 'error',
}
/**
* Log level priority for filtering
*/
const LOG_LEVEL_PRIORITY: Record<LogLevel, number> = {
[LogLevel.DEBUG]: 0,
[LogLevel.INFO]: 1,
[LogLevel.WARN]: 2,
[LogLevel.ERROR]: 3,
};
/**
* Log entry context information
*/
export interface LogContext {
method?: string;
params?: any;
error?: any;
duration?: number;
[key: string]: any;
}
/**
* Structured log entry
*/
export interface LogEntry {
timestamp: string;
level: LogLevel;
message: string;
context?: LogContext;
}
/**
* Logger class for structured logging
* Outputs to stderr with configurable log levels
*
* Requirements: 7.1, 7.4, 7.5
*/
export class Logger {
private enabled: boolean;
private level: LogLevel;
/**
* Create a new Logger instance
*
* @param enabled - Whether logging is enabled
* @param level - Minimum log level to output
*/
constructor(enabled: boolean = true, level: LogLevel = LogLevel.INFO) {
this.enabled = enabled;
this.level = level;
}
/**
* Check if a log level should be output
*
* @param level - Log level to check
* @returns true if the level should be logged
*/
private shouldLog(level: LogLevel): boolean {
if (!this.enabled) {
return false;
}
return LOG_LEVEL_PRIORITY[level] >= LOG_LEVEL_PRIORITY[this.level];
}
/**
* Format a log entry as a string
*
* @param entry - Log entry to format
* @returns Formatted log string
*/
private formatLogEntry(entry: LogEntry): string {
const parts = [
`[${entry.timestamp}]`,
`[${entry.level.toUpperCase()}]`,
entry.message,
];
if (entry.context && Object.keys(entry.context).length > 0) {
// Format context as JSON for structured logging
parts.push(JSON.stringify(entry.context));
}
return parts.join(' ');
}
/**
* Write a log entry to stderr
*
* @param level - Log level
* @param message - Log message
* @param context - Optional context information
*/
private log(level: LogLevel, message: string, context?: LogContext): void {
if (!this.shouldLog(level)) {
return;
}
const entry: LogEntry = {
timestamp: new Date().toISOString(),
level,
message,
context,
};
// Write to stderr to avoid interfering with stdio transport
console.error(this.formatLogEntry(entry));
}
/**
* Log a debug message
*
* @param message - Debug message
* @param context - Optional context information
*/
debug(message: string, context?: LogContext): void {
this.log(LogLevel.DEBUG, message, context);
}
/**
* Log an info message
*
* @param message - Info message
* @param context - Optional context information
*/
info(message: string, context?: LogContext): void {
this.log(LogLevel.INFO, message, context);
}
/**
* Log a warning message
*
* @param message - Warning message
* @param context - Optional context information
*/
warn(message: string, context?: LogContext): void {
this.log(LogLevel.WARN, message, context);
}
/**
* Log an error message
*
* @param message - Error message
* @param context - Optional context information
*/
error(message: string, context?: LogContext): void {
this.log(LogLevel.ERROR, message, context);
}
/**
* Set the log level
*
* @param level - New log level
*/
setLevel(level: LogLevel): void {
this.level = level;
}
/**
* Enable or disable logging
*
* @param enabled - Whether logging should be enabled
*/
setEnabled(enabled: boolean): void {
this.enabled = enabled;
}
/**
* Get the current log level
*
* @returns Current log level
*/
getLevel(): LogLevel {
return this.level;
}
/**
* Check if logging is enabled
*
* @returns true if logging is enabled
*/
isEnabled(): boolean {
return this.enabled;
}
}
/**
* Create a logger instance from configuration
*
* @param enabled - Whether logging is enabled
* @param level - Log level string
* @returns Logger instance
*/
export function createLogger(
enabled: boolean,
level: 'debug' | 'info' | 'warn' | 'error'
): Logger {
return new Logger(enabled, level as LogLevel);
}
