SlackLogDevice

LogDevice implementation that post logs on a Slack channel.

Just add this into your Gemfile:

gem 'slack_log_device'

Then, just run a bundle install.

require 'slack_log_device'

logger = Logger.new(SlackLogDevice.new(webhook_url: 'https://hooks.slack.com/services/...', username: 'MyApp'))
logger.level = Logger::INFO
logger.warn('BAM!')

Then, the logged message will be writen to webhook's configured channel.

Note that the messages written are buffered in order to avoid consecutive request.

• auto_flush: To flush messages directly when a message is written (disabled by default).
• channel: The channel to post message on (webhook configured channel by default). It can be a channel (if starting with #) or a specific user (if starting with a @).
• flush_delay: The delay in seconds to send buffered messages (1 by default).
• max_buffer_size: The max messages count to flush them (10 messages by default).
• timeout: The timeout in seconds to send message to slack (5 by default).
• username: The username to post message as (nil by default).
• webhook_url: The URL of the webhook (mandatory).

slack_log_device provides a log formatter to have a pretty output for slack. It can be configured like this:

logger.formatter = SlackLogDevice.formatter

SlackLogDevice.formatter method also accepts block to transform logged message, example:

logger.formatter = SlackLogDevice.formatter { |message| message.reverse }

By default, formatter adds those metadata:

• PID: The current process id.
• User: The current user (ENV['USER']).
• Machine: The machine name (hostname).

To disable default metadata (User, Machine and PID), set disable_default_metadata formatter option to true.

You can also add custom metadata to message sent to slack, here is how to do it:

logger.formatter = SlackLogDevice.formatter(extra_metadata: {
  'Exception class' => -> (options) { options[:exception].class.name },
  'System' => `uname -a`,
})

As you can see, blocks (invoked with options contains request and exception) are supported.

Exception backtrace is automatically stripped to 10 lines. You can change this behavior via :max_backtrace_lines:

logger.formatter = SlackLogDevice.formatter(max_backtrace_lines: 50)

• A value of 0 will not print backtrace.
• A value of -1 will not strip backtrace.

If you use Ruby on Rails, you will get some metadata like current HTTP method, URL, remote address and User-Agent (see Rails configuration section).

If you need more, use :extra_metadata option. Note that blocks specified with :extra_metadata option are invoked with options that may contains :request option (if present).

By default, there is a different icon emoji for each logging severity level. But, it can be configured:

logger.formatter = SlackLogDevice.formatter(max_backtrace_lines: 50, icon_emojis: { fatal: ':metal:', warn: ':skull:' })

Or for all severity levels:

logger.formatter = SlackLogDevice.formatter(max_backtrace_lines: 50, icon_emoji: ':metal:')

For a rails application, it is recommanded to use following configuration into config/environments/production.rb file:

SlackLogDevice.enable_rails_logging!
config.logger = ActiveSupport::Logger.new(SlackLogDevice.new(webhook_url: 'https://hooks.slack.com/services/...', username: 'MyRailsApp'))
config.logger.formatter = SlackLogDevice.formatter
config.log_level = :warn

SlackLogDevice.enable_rails_logging! instruction put current request into thread in order to make it available by slack formatter.

This project is fully tested with Rspec 3. Just run bundle exec rake (after a bundle install).