cloud-gov-instructions logging.instructions.md

Cloud.gov Logging Instructions

This document provides guidance for implementing logging and monitoring in cloud.gov applications.

Overview

Cloud.gov automatically captures logs written to stdout and stderr. Applications should:

• Write all logs to stdout/stderr (not files)
• Use structured logging (JSON format recommended)
• Include contextual information for debugging
• Never log sensitive data (PII, credentials, tokens)

Viewing Logs

Recent Logs

# View recent logs (last ~100 lines)
cf logs my-app --recent

Stream Live Logs

# Stream logs in real-time
cf logs my-app

# Press Ctrl+C to stop streaming

Log Types

Cloud.gov provides several log types:

Type	Source	Description
APP	Application	Your application's stdout/stderr
RTR	Router	HTTP request logs
STG	Staging	Build/staging process logs
CELL	Cell	Container lifecycle events
API	Cloud Controller	CF CLI operations

Filter Logs

# View only application logs (grep for APP)
cf logs my-app --recent | grep "\[APP"

# View only router logs
cf logs my-app --recent | grep "\[RTR"

Application Logging

Basic Logging Configuration

Python

import logging
import sys

# Configure logging to stdout
logging.basicConfig(
    level=logging.INFO,
    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
    handlers=[logging.StreamHandler(sys.stdout)]
)

logger = logging.getLogger(__name__)

# Log messages
logger.info("Application started")
logger.warning("Something might be wrong")
logger.error("An error occurred")

Node.js

const winston = require('winston');

const logger = winston.createLogger({
  level: 'info',
  format: winston.format.combine(
    winston.format.timestamp(),
    winston.format.json()
  ),
  transports: [
    new winston.transports.Console()
  ]
});

// Log messages
logger.info('Application started');
logger.warn('Something might be wrong');
logger.error('An error occurred');