How to log rotate in Ruby

In Ruby, you can implement log rotation by using a combination of the Logger class and external tools or libraries. Log rotation involves managing log files to prevent them from becoming too large and unmanageable. It typically includes creating new log files when the current one reaches a certain size or at specific time intervals.

Here's a basic example of log rotation using the Logger class and a simple custom implementation:

require 'logger'
require 'fileutils'

LOG_FILE = 'application.log'

# Create a logger instance and specify the log file
logger = Logger.new(LOG_FILE, 'daily')  # Log will be rotated daily

# Customize the log message format (optional)
logger.formatter = proc do |severity, datetime, progname, msg|
  "#{datetime.strftime('%Y-%m-%d %H:%M:%S')} [#{severity}] #{msg}\n"
end

# Set the log level (e.g., INFO)
logger.level = Logger::INFO

# Log some messages
logger.info("This is an info message")
logger.warn("This is a warning message")
logger.error("This is an error message")
logger.fatal("This is a fatal message")

# Rotate the log manually (example, you can implement more sophisticated rules)
def rotate_log(file)
  return unless File.exist?(file)

  timestamp = Time.now.strftime('%Y%m%d%H%M%S')
  rotated_file = "#{file}.#{timestamp}"
  FileUtils.mv(file, rotated_file)
end

# Perform log rotation (example, you can implement your own rotation logic)
rotate_log(LOG_FILE)

In the example above, we create a logger instance with the option 'daily', which means the log file will be rotated daily. You can use other options for rotation, such as 'weekly', 'monthly', or you can implement a custom rotation logic by providing a frequency (in seconds) as the second argument to Logger.new.

For more complex log rotation strategies, you may want to consider using a dedicated log rotation library or a system-level log rotation tool (such as logrotate on Unix-like systems). These external tools typically offer more advanced features like compression, log retention policies, and log archiving. For instance, on Unix-like systems, you can use logrotate by creating a configuration file for your application's log file and configuring the rotation rules as needed.

Keep in mind that the above example is a basic illustration, and actual log rotation requirements may vary depending on the specific needs of your application and the environment in which it runs.

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