Monitoring and Logging Best Practices for Node.js Applications

{
  "title": "Monitoring and Logging Best Practices for Node.js Applications",
  "description": "Implementing effective monitoring and logging strategies in Node.js applications to track performance and diagnose issues.",
  "category": "Node.js Cursor Rules",
  "rules": [
    {
      "id": "nodejs-logging-library",
      "description": "Use a robust logging library such as Winston, Bunyan, or Pino instead of console.log for enhanced functionality and flexibility.",
      "severity": "warning",
      "pattern": "console\\.log\\(.*\\);",
      "replacement": "logger.info($1);",
      "example": {
        "bad": "console.log('User logged in');",
        "good": "logger.info('User logged in');"
      }
    },
    {
      "id": "nodejs-structured-logging",
      "description": "Implement structured logging using JSON format to facilitate easier parsing and analysis of log data.",
      "severity": "warning",
      "pattern": "logger\\.(info|warn|error)\\((?!\\{).*\\);",
      "replacement": "logger.$1({ message: $1 });",
      "example": {
        "bad": "logger.info('User logged in');",
        "good": "logger.info({ message: 'User logged in' });"
      }
    },
    {
      "id": "nodejs-log-levels",
      "description": "Utilize appropriate log levels (e.g., info, warn, error) to categorize log messages based on their severity.",
      "severity": "warning",
      "pattern": "logger\\.log\\(.*\\);",
      "replacement": "logger.info($1);",
      "example": {
        "bad": "logger.log('User logged in');",
        "good": "logger.info('User logged in');"
      }
    },
    {
      "id": "nodejs-log-timestamps",
      "description": "Include timestamps in log entries to provide context about when events occurred.",
      "severity": "warning",
      "pattern": "logger\\.(info|warn|error)\\(\\{.*\\}\\);",
      "replacement": "logger.$1({ timestamp: new Date().toISOString(), ...$1 });",
      "example": {
        "bad": "logger.info({ message: 'User logged in' });",
        "good": "logger.info({ timestamp: new Date().toISOString(), message: 'User logged in' });"
      }
    },
    {
      "id": "nodejs-log-sensitive-data",
      "description": "Avoid logging sensitive information such as passwords, credit card numbers, or personal data.",
      "severity": "error",
      "pattern": "logger\\.(info|warn|error)\\(.*(password|creditCard|ssn).*\\);",
      "replacement": "",
      "example": {
        "bad": "logger.info('User password: ' + user.password);",
        "good": "logger.info('User logged in', { userId: user.id });"
      }
    },
    {
      "id": "nodejs-log-rotation",
      "description": "Implement log rotation to prevent log files from consuming excessive disk space.",
      "severity": "warning",
      "pattern": "new winston\\.transports\\.File\\(\\{ filename: '.*\\.log' \\}\\)",
      "replacement": "new winston.transports.File({ filename: 'application.log', maxsize: 10485760, maxFiles: 5 })",
      "example": {
        "bad": "new winston.transports.File({ filename: 'application.log' })",
        "good": "new winston.transports.File({ filename: 'application.log', maxsize: 10485760, maxFiles: 5 })"
      }
    },
    {
      "id": "nodejs-centralized-logging",
      "description": "Configure centralized logging to aggregate logs from multiple sources for unified analysis.",
      "severity": "info",
      "pattern": "",
      "replacement": "",
      "example": {
        "bad": "",
        "good": "const { createLogger, transports } = require('winston');\nconst { LogstashTransport } = require('winston-logstash-transport');\n\nconst logger = createLogger({\n  transports: [\n    new transports.Console(),\n    new LogstashTransport({\n      host: 'logstash.example.com',\n      port: 5000\n    })\n  ]\n});"
      }
    },
    {
      "id": "nodejs-monitoring-tools",
      "description": "Integrate monitoring tools like Prometheus and Grafana to track application performance metrics.",
      "severity": "info",
      "pattern": "",
      "replacement": "",
      "example": {
        "bad": "",
        "good": "const client = require('prom-client');\nconst express = require('express');\nconst app = express();\n\nconst collectDefaultMetrics = client.collectDefaultMetrics;\ncollectDefaultMetrics({ timeout: 5000 });\n\napp.get('/metrics', (req, res) => {\n  res.set('Content-Type', client.register.contentType);\n  res.end(client.register.metrics());\n});"
      }
    }
  ]
}