Ruby on Rails

Monitoring & Logging

Rails.logger, log levels, Sentry, New Relic, ActiveSupport::Notifications, tracing, correlation IDs, observability

20 câu hỏi phỏng vấn·
Senior
1

What is the default logger used in a Rails application?

Câu trả lời

Rails uses Rails.logger as the main access point to the logging system. By default, it is an instance of ActiveSupport::Logger that writes to files like log/development.log, log/production.log, etc., depending on the environment. This logger is automatically configured at application startup and is accessible from anywhere in the Rails code.

2

What are the five log levels available in Rails, from least to most critical?

Câu trả lời

Rails uses five standard log levels: debug (detailed information for development), info (general operational information), warn (non-blocking warnings), error (recoverable errors), and fatal (critical errors causing shutdown). Each level filters out lower-level messages, allowing verbosity adjustment based on environment.

3

How to configure the log level in production in Rails?

Câu trả lời

The production log level is configured in config/environments/production.rb via config.log_level. The default value is :info to avoid generating too much data in production. It is also possible to set the level dynamically via an environment variable like ENV.fetch('RAILS_LOG_LEVEL', 'info').to_sym for maximum flexibility without redeployment.

4

How to log a message with structured data in Rails to facilitate analysis?

5

What is the difference between Rails.logger.debug and Rails.logger.debug { } with a block?

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