ConditionChecker !! WIP !!

ConditionChecker is a gem that provides a way to compose and run conditionals and inspect failures.

Say you have a simple page that checks your web app's health by checking a few metrics. Some checks are more complex and require checking a few things, but when they fail you want to know exactly what part failed. Some checks are less important, so you want to show them in a different way, even if they might contain some conditions of a more critical check. Or you want to show these checks in a human-readable way, labelling them or integrating with I18n.

Installation

Add this line to your application's Gemfile:

gem 'condition_checker'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install condition_checker

Structure

• ConditionChecker::Mixin is the main module that provides the DSL's condition and check methods. (see below for usage).

• A check is a named collection of conditions with a single success/fail status. It can have one more more conditions

• A condition is a named rule that evaluates to either success or failure when run against an object. Each condition holds callable code (a proc/lambda/class with call method) that runs its condition check and returns a result.

You can get the results of all checks by calling your instance's checks method. successes and fails return a subset of checks. If you are not interested in specific checks, you can use success? and fail? to get the overall status.

Usage

Basic Setup

class WebsiteHealth
  extend ConditionChecker::Mixin

  # Define individual conditions
  condition "database.connected", ->(website) { website.database_connected? }
  condition "api.healthy", ->(website) { website.api_healthy? }
  condition "memory.optimal", MemoryChecker  # calls MemoryChecker.call(website)
  condition "response_time.acceptable", ResponseTimeChecker

  # Conditions can also just be a method
  def everything_ok
    context.everything_ok?
  end

  # Group conditions into meaningful checks
  check :critical_services, conditions: ["database.connected", "api.healthy"]
  check "performance.ok", conditions: ["memory.optimal", "response_time.acceptable"]
  check :all_systems_go, conditions: ["database.connected", "api.healthy", "memory.optimal", "response_time.acceptable", "everything_ok"]
end

Running Checks

# Create a checker instance for your object
checker = WebsiteHealth.for(website) 

checker.context # passed in object can be accessed as `context` in methods

# Check if everything passed
if checker.fails.empty?
  puts "All systems operational!"
else
  puts "Found #{checker.fails.size} failing checks"
end

# Get specific check results
critical_services = checker["critical_services"] # or checker.check("critical_services")
if critical_check.success?
  puts "Critical services are up!"
else
  puts "Critical service issues: #{critical_check.fails.map(&:name).join(', ')}"
end

# Get all failing conditions
checker.fails.map do |check|
  check.conditions.map do |condition|
    [condition.name, condition.value, condition.result.value] # ["database.connected", true, true]
  end
end

# Example
class SystemMonitor
  def self.generate_health_report(website)
    checker = WebsiteHealth.for(website)
    
    {
      status: checker.fail? ? :unhealthy : :healthy,
      total_checks: checker.checks.size,
      failing_checks: checker.fails.size,
      critical_services: checker.checks.find("critical_services").success?,
      failures: checker.fails.map { |check|
        {
          check: check.name,
          failed_conditions: check.fails.map(&:name)
        }
      }
    }
  end
end

Development

After checking out the repo, run bundle install to install dependencies. Then, run rspec to run the tests.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/modsognir/condition_checker.