Heroku logging not working

Question

I've got a rails 3.1 app deployed on Heroku Cedar. I'm having a problem with the logging. The default rails logs are working just fine, but when I do something like:

logger.info "log this message"

In my controller, Heroku doesn't log anything. When I deploy my app I see the heroku message "Injecting rails_log_stdout" so I think calling the logger should work just fine. Puts statements end up in my logs. I've also tried other log levels like logger.error. Nothing works. Has anyone else seen this?

Pacificas

@geekazoid 's answer below is the correct one now. https://mcmap.net/q/756173/-heroku-logging-not-working – Richert

Answer 1

I was just having the same issue, solved by using the technique here:

https://github.com/ryanb/cancan/issues/511

Basically, you need to specify the logger outputs to STDOUT, some gems interfere with the logger and seem to hijack the functionality (cancan in my case).

For the click lazy, just put this in environments/production.rb

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

Cocaine

Heroku support was leading me in a similar direction. Here is a list of gems they claim cause this problem: acts_as_audited, on_the_spot, restful_jsonp, authlogic, cancan, simple-navigation – Pacificas

the second line should be config.logger.level = Logger::INFO – Nero

Answer 2

MBHNYC's answer works great, but it makes it difficult to change the log level in different environments without changing the code. You can use this code in your environments/production.rb to honor an environment variable as well as have a reasonable default:

# https://github.com/ryanb/cancan/issues/511
config.logger = Logger.new(STDOUT)
config.logger.level = Logger.const_get((ENV["LOG_LEVEL"] || "INFO").upcase)

Use this command to set a different log level:

heroku config:set LOG_LEVEL=error

Hanukkah

Excellent Phil, this is a superior solution. – Cocaine

I have modified this to upcase the string before it's passed to const_get, which is case-sensitive. Otherwise you might get an error from Heroku if you set the LOG_LEVEL variable to a lowercase value: 2012-12-05T21:38:14+00:00 app[worker.1]: wrong constant name debug – Hanukkah

It seems that Heroku removed reverences to LOG_LEVEL from their docs within a month or so of this answer. Currently, it seems it would be better to do this: config.log_level = ENV['LOG_LEVEL'] ? ENV['LOG_LEVEL'].to_sym : :info – Grussing

@user664833: I've updated the answer to make it clear LOG_LEVEL doesn't get any special treatment by Heroku anymore. What's superior about setting this as a symbol as opposed to as a constant? I tend to prefer my answers to be "what I've got in production" so I know they work, but I'm curious now. – Hanukkah

@PhilCalvin, in Rails 4 the default config/environments/production.rb uses a symbol (config.log_level = :info), so I followed suit. As a matter of taste, I find the code in my previous comment to look cleaner. And the capitalization and use of upcase are also relics now. Further, in Rails 4 you will likely be using rails_12factor, which depends on rails_stdout_logging, which ensures that your logs will be sent to standard out. Note that rails_stdout_logging also supports Rails 3. – Grussing

Answer 3

As of the moment, it looks like heroku injects these two plugins when building the slug:

rails_log_stdout - https://github.com/ddollar/rails_log_stdout

rails3_server_static_assets - https://github.com/pedro/rails3_serve_static_assets

Anything sent to the pre-existing Rails logger will be discarded and will not be visible in logs. Just adding this for completeness for anyone else who ends up here.

Nero

That's wrong. What Heroku does is dump its own output to stdout. That's why you are supposed to set your rails to dump into stdout as well – Scurrilous

To clarify, what part of what I said are you thinking is wrong? Yes, heroku sends output to stdout. The plugin addresses this by replacing the logger with a logger that logs to stdout. Anything logged before the logger is replaced to the original Rails logger will never be visible. – Nero

Sorry, I'm not sure how it all really works at this point. BTW, the plugin you mentioned in your answer is not the plugin that Heroku currently injects – Scurrilous

Answer 4

The problem, as @MBHNYC correctly addressed, is that your logs are not going to STDOUT.

Instead of configuring manually all that stuff, Heroku provides a gem that does this all for you.

Just put

gem 'rails_12factor', group: :production

in your Gemfile, bundle, and that's it!

NOTE: This works both for Rails 3 and 4.

Source: Rails 4 on Heroku

Selah

OMG thank you for this. Just wasted like a day of debugging because I grouped this gem into the wrong environment so logs were not showing up. – Peursem