Logs not printing to STDOUT

[sudhirj]

Apps with the rails_12factor gem / apps running on Heroku need to print logs to STDOUT - but falcon seems to be blocking this. On Heroku it dumps the logs only on exit. Can we have logging behaviour respected / flushed when the app is trying to log to STDOUT?

[ioquatix]

Thanks for the report.

I'm not completely sure I understand the problem.

I'm running a demo app in Heroku and the logs come out just fine:

So, I don't believe logging goes to STDOUT but goes to STDERR:

https://github.com/socketry/async/blob/master/lib/async/logger.rb#L42

Do you mind showing me how you are starting falcon (do you include --verbose) and do you mind showing me the log output window on Heroku after running some requests?

[sudhirj]

Here's what I mean - only the Heroku router logs are shown when the requests are made, but when I restart and SIGTERM is sent, all the logs are dumped.

This is the Rails 5.2.1 with the RAILS_LOG_TO_STDOUT=enabled, with the default production.rb settings.

if ENV["RAILS_LOG_TO_STDOUT"].present?
    logger           = ActiveSupport::Logger.new(STDOUT)
    logger.formatter = config.log_formatter
    config.logger    = ActiveSupport::TaggedLogging.new(logger)
end

[sudhirj]

Not using verbose mode, start command is web: bundle exec falcon serve --port $PORT --bind http://0.0.0.0

[ioquatix]

I just deployed the latest version of falcon and https://github.com/socketry/utopia-falcon-heroku to Heroku and the logging is certainly happening in real time as I make individual requests.

I took a look at rails_12factor and see that it pulls in the following code:

https://github.com/heroku/rails_stdout_logging/blob/master/lib/rails_stdout_logging/rails.rb#L2-L4

It seems to me that it's likely to stop ::Logger from working correctly. I'd say the issue here is not with Falcon (which uses ::Logger) and with rails_stdout_logging which is breaking ::Logger.