Rails STDOUT 日志没有出现在 kubectl 日志和 datadog 日志中

Question

We have set logger as STDOUT in the rails configuration.

  config.log_level = :info
  config.logger = Logger.new(STDOUT)

We are expecting these logs in kubectl logs as well as datadog logs but STDOUT is not showing up there. We tried below code to test it.

def method_name
  system('echo testing logging') - this shows up in kubectl/datadog logs
  Rails.logger.info('STDOUT - testing logging') - this does not show up in kubectl/datadog log
end

Answer 1

We have changed the logger setting to output the logs to container file descriptor.

Reference: https://blog.eq8.eu/til/ruby-logs-and-puts-not-shown-in-docker-container-logs.html

Answer 2

Try to use the default config and make sure to set the environment variable RAILS_LOG_TO_STDOUT=true , for your deployment/replica set, and in production mode ( RAILS_ENV=production ). (In dev mode it always logs to console per default).

Actually, the official rails docker images used to have that set, but the newer recommended ruby docker images - of course - do not have Rails specific environment variables set.

(more: search for RAILS_LOG_TO_STDOUT in the release notes here , and see PR here )