System Health

The System Health gem can be added to your Rails application to provide a convenient way to regularly look for bad data or other system health indicators.

Add this line to your application's Gemfile:

gem 'system_health'

And then execute:

$ bundle

Or install it yourself as:

$ gem install system_health

and then...

All monitoring classes require a public instance method named description. This method should return a string describing the bad data condition that is being tested.

For example, in lib/system_health/monitors/bad_data.rb create:

module SystemHealth
  module Monitors
    class BadData < Base
      def description
        'Bad data was discovered'
      end

      private

      def bad_data?
        # return true from this method if there is bad data
      end
    end
  end
end

the private instance method bad_data? should return true when bad data exists. Note: this class inherits from Base.

For example, in lib/system_health/monitors/bad_sql_data.rb create:

module SystemHealth
  module Monitors
    class BadSqlData < Sql
      def description
        'Bad data was discovered through a SQL query'
      end

      private

      def sql
        <<-SQL
          SELECT *
          FROM some_table
          WHERE bad_data is true
        SQL
      end
    end
  end
end

the private instance method sql should include the string version of the SQL to use in the system health check. This SQL should return rows when there is bad data. I.e. no rows returned means no system health problem. Rows returned means there is a problem. Note: this class inherits from Sql.

SystemHealth.configure do |config|
  config.monitor_classes = [
    SystemHealth::Monitors::BadData,
    SystemHealth::Monitors::BadSqlData
  ]
end

The System Health gem exposes a monitoring class SystemHealth::Monitor that can be used to test for all system health issues with the following methods:

mon = SystemHealth::Monitor.new
mon.error_messages
mon.error_count

by default SystemHealth::Monitor.new uses those classes defined in your initializer but you can initialize with your own classes, if you wish:

mon =
SystemHealth::Monitor.new([SystemMonitor::Monitors::SomeSpecialClass])
mon.error_messages
mon.error_count

You are free to do as you wish with the results from error_messages and error_count. A common approach might be to create a simple controller that responds with any errors. Or, you could create rake task that sends an email to some list when errors are discovered.

1. Add concept of notifiers to make it more seamless to email or report on system health issues.
2. Add monitor classes so different classes can be run at different times and with different frequency.

1. Fork it ( https://github.com/[my-github-username]/system_health/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

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