Make Your Logs Work for You

The days of logging in to servers and manually viewing log files are over. SolarWinds® Papertrail™ aggregates logs from applications, devices, and platforms to a central location.

View Technology Info

FEATURED TECHNOLOGY

Troubleshoot Fast and Enjoy It

SolarWinds® Papertrail™ provides cloud-based log management that seamlessly aggregates logs from applications, servers, network devices, services, platforms, and much more.

View Capabilities Info

FEATURED CAPABILITIES

Aggregate and Search Any Log

SolarWinds® Papertrail™ provides lightning-fast search, live tail, flexible system groups, team-wide access, and integration with popular communications platforms like PagerDuty and Slack to help you quickly track down customer problems, debug app requests, or troubleshoot slow database queries.

View Languages Info

FEATURED LANGUAGES

TBD - APM Integration Title

TBD - APM Integration Description

TBD Link

APM Integration Feature List

TBD - Built for Collaboration Title

TBD - Built for Collaboration Description

TBD Link

Built for Collaboration Feature List

Join SolarWinds Day October 19 to see the next evolution in observability. Register now.

Collect Logs: Apps & Services > Unicorn

Unicorn

Unicorn is a high-performance forking Web server that is often used for serving Ruby on Rails applications.

Many times, its logging configuration leads implementors to re-instantiate Rails’ logger object, and in the process, to unintentionally log at DEBUG log level (with SQL statements, cache hits, and other events that are often not necessary).

Here’s how to change the log level of a Rails app served by Unicorn.

Problem

Unicorn doesn’t load Rails::Rack::LogTailer, which is what outputs most Rails logs to STDOUT. This isn’t an inherent problem, it’s simply a different approach to logging.

Often this leads someone to instantiate a new Logger in the environment-specific Rails initializer which in the process sets the log level to DEBUG verbosity.

Solution

Here’s how to replicate similar behavior as exists with most other Rails Web servers.

To output logs to STDOUT and define the log level, edit config/environments/<environment>.rb, such as production.rb. In the MyApp::Configuration.configure .. end block, add these 3 lines:

config.logger = Logger.new(STDOUT)
config.logger.level = Logger.const_get('INFO')
config.log_level = :info

These create a new Logger class that outputs to STDOUT, then changes the logging level in that newly-instantiated logger (to an integer, as returned by const_get).

Finally, it sets Rails’ log_level to the equivalent symbol so that any other callers, such as Heroku’s rails_12factor gem, also see the updated level (example: rails_stdout_logging).

Comment out any existing assignments of config.logger or config.log_level in the file.

Advanced options

Use existing logger

The example above creates a new logger (to STDOUT) and sets its log level. If you want to leave the log destination as-is and only change its log level, use this instead of the lines above:

config.logger.level = Logger.const_get('INFO')
config.log_level = :info

Instead of redefining config.logger and setting its level, this simply sets level on the existing config.logger.

Read log level from env variable

To set the log level as an environment variable (like when using Heroku config variables), use this instead of the lines above:

config.logger = Logger.new(STDOUT)
config.logger.level = Logger.const_get(ENV['LOG_LEVEL'] ? ENV['LOG_LEVEL'].upcase : 'INFO')
config.log_level = (ENV['LOG_LEVEL'] ? ENV['LOG_LEVEL'].downcase : 'info').to_sym

This will use the LOG_LEVEL environmental variable when it is set and INFO when it is not set.

Unicorn on Heroku

As of this writing, A Rails 3.1.3 app using Unicorn 4.1.1 on Heroku (cedar) outputs few or no app logs in its initial configuration. Read more here or here.

When a Rails app is deployed, Heroku injects rails_log_stdout, which redefines Rails’ Logger so all output goes to STDOUT. This doesn’t work as expected with Unicorn, so only rack output is logged.

To re-enable logging to STDOUT like Heroku expects, use the example in Read log level from env variable above.

Use heroku config:add to set the desired log level of the Heroku app. For example:

$ heroku config:add LOG_LEVEL="warn"

The app will restart immediately at the new log level.

Disable rails_log_stdout (optional)

Optionally, you can tell Heroku not to inject rails_log_stdout since it’s no longer relevant with Unicorn.

To do so, create an empty vendor/plugins/rails_log_stdout/ directory containing a placeholder file and commit it to your git repo:

$ mkdir -p vendor/plugins/rails_log_stdout
$ touch vendor/plugins/rails_log_stdout/keep_me
$ git add vendor/plugins/rails_log_stdout/keep_me
$ git commit -m "Placeholder file to disable rails_log_stdout" vendor/plugins/rails_log_stdout/keep_me
The scripts are not supported under any SolarWinds support program or service. The scripts are provided AS IS without warranty of any kind. SolarWinds further disclaims all warranties including, without limitation, any implied warranties of merchantability or of fitness for a particular purpose. The risk arising out of the use or performance of the scripts and documentation stays with you. In no event shall SolarWinds or anyone else involved in the creation, production, or delivery of the scripts be liable for any damages whatsoever (including, without limitation, damages for loss of business profits, business interruption, loss of business information, or other pecuniary loss) arising out of the use of or inability to use the scripts or documentation.