Back to Repositories

Testing Metrics Plugin Implementation in Fluentd

This test suite validates the metrics plugin functionality in Fluentd, focusing on counter and gauge metric implementations. It ensures proper metric registration, configuration, and operation of various metric types through comprehensive unit testing.

Test Coverage Overview

The test suite provides extensive coverage of Fluentd’s metrics plugin functionality, examining both counter and gauge metric implementations.

Key areas tested include:

Basic and aliased counter metrics operations
Gauge metric functionality with increment/decrement operations
Plugin configuration and initialization
Error handling for unimplemented methods

Implementation Analysis

The testing approach uses multiple test classes to verify different metric implementations, including bare, basic, and aliased versions of both counter and gauge metrics.

Testing patterns include:

Inheritance-based test structure using sub_test_case blocks
Setup methods for consistent test initialization
Systematic verification of metric operations
Exception handling validation

Technical Details

Testing infrastructure includes:

Test::Unit framework for Ruby
Fluent::Plugin::Metrics base class
Custom metric implementations for testing
Configuration elements for plugin setup
Method aliasing for alternative implementations

Best Practices Demonstrated

The test suite exemplifies strong testing practices through organized, systematic validation of functionality.

Notable practices include:

Isolated test cases for each metric type
Comprehensive method coverage
Clear setup and teardown procedures
Explicit error case validation
Consistent assertion patterns

fluent/fluentd

test/plugin/test_metrics.rb

            
require_relative '../helper'
require 'fluent/plugin/metrics'
require 'fluent/plugin/base'
require 'fluent/system_config'

class BareMetrics < Fluent::Plugin::Metrics
  Fluent::Plugin.register_metrics('bare', self)

  private

  # Just override for tests.
  def has_methods_for_counter?
    false
  end
end

class BasicCounterMetrics < Fluent::Plugin::Metrics
  Fluent::Plugin.register_metrics('example', self)

  attr_reader :data

  def initialize
    super
    @data = 0
  end
  def get
    @data
  end
  def inc
    @data +=1
  end
  def add(value)
    @data += value
  end
  def set(value)
    @data = value
  end
  def close
    @data = 0
    super
  end
end

class AliasedCounterMetrics < Fluent::Plugin::Metrics
  Fluent::Plugin.register_metrics('example', self)

  attr_reader :data

  def initialize
    super
    @data = 0
  end
  def configure(conf)
    super
    class << self
      alias_method :set, :set_counter
    end
  end
  def get
    @data
  end
  def inc
    @data +=1
  end
  def add(value)
    @data += value
  end
  def set_counter(value)
    @data = value
  end
  def close
    @data = 0
    super
  end
end

class BasicGaugeMetrics < Fluent::Plugin::Metrics
  Fluent::Plugin.register_metrics('example', self)

  attr_reader :data

  def initialize
    super
    @data = 0
  end
  def get
    @data
  end
  def inc
    @data +=1
  end
  def dec
    @data -=1
  end
  def add(value)
    @data += value
  end
  def sub(value)
    @data -= value
  end
  def set(value)
    @data = value
  end
  def close
    @data = 0
    super
  end
end

class AliasedGaugeMetrics < Fluent::Plugin::Metrics
  Fluent::Plugin.register_metrics('example', self)

  attr_reader :data

  def initialize
    super
    @data = 0
  end
  def configure(conf)
    super
    class << self
      alias_method :dec, :dec_gauge
      alias_method :set, :set_gauge
      alias_method :sub, :sub_gauge
    end
  end
  def get
    @data
  end
  def inc
    @data +=1
  end
  def dec_gauge
    @data -=1
  end
  def add(value)
    @data += value
  end
  def sub_gauge(value)
    @data -= value
  end
  def set_gauge(value)
    @data = value
  end
  def close
    @data = 0
    super
  end
end

class StorageTest < Test::Unit::TestCase
  sub_test_case 'BareMetrics' do
    setup do
      @m = BareMetrics.new
      @m.configure(config_element())
    end

    test 'is configured with plugin information and system config' do
      m = BareMetrics.new
      m.configure(config_element('metrics', '', {}))

      assert_false m.use_gauge_metric
      assert_false m.has_methods_for_counter
      assert_false m.has_methods_for_gauge
    end

    test 'all bare operations are not defined yet' do
      assert_raise NotImplementedError do
        @m.get
      end
      assert_raise NotImplementedError do
        @m.inc
      end
      assert_raise NotImplementedError do
        @m.dec
      end
      assert_raise NotImplementedError do
        @m.add(10)
      end
      assert_raise NotImplementedError do
        @m.sub(11)
      end
      assert_raise NotImplementedError do
        @m.set(123)
      end
    end
  end

  sub_test_case 'BasicCounterMetric' do
    setup do
      @m = BasicCounterMetrics.new
      @m.configure(config_element('metrics', '', {'@id' => '1'}))
    end

    test 'all basic counter operations work well' do
      assert_true @m.has_methods_for_counter
      assert_false @m.has_methods_for_gauge

      assert_equal 0, @m.get
      assert_equal 1, @m.inc

      @m.add(20)
      assert_equal 21, @m.get
      assert_raise NotImplementedError do
        @m.dec
      end

      @m.set(100)
      assert_equal 100, @m.get
      assert_raise NotImplementedError do
        @m.sub(11)
      end
    end
  end

  sub_test_case 'AliasedCounterMetric' do
    setup do
      @m = AliasedCounterMetrics.new
      @m.configure(config_element('metrics', '', {}))
    end

    test 'all aliased counter operations work well' do
      assert_true @m.has_methods_for_counter
      assert_false @m.has_methods_for_gauge

      assert_equal 0, @m.get
      assert_equal 1, @m.inc

      @m.add(20)
      assert_equal 21, @m.get
      assert_raise NotImplementedError do
        @m.dec
      end

      @m.set(100)
      assert_equal 100, @m.get
      assert_raise NotImplementedError do
        @m.sub(11)
      end
    end
  end

  sub_test_case 'BasicGaugeMetric' do
    setup do
      @m = BasicGaugeMetrics.new
      @m.use_gauge_metric = true
      @m.configure(config_element('metrics', '', {}))
    end

    test 'all basic gauge operations work well' do
      assert_false @m.has_methods_for_counter
      assert_true @m.has_methods_for_gauge

      assert_equal 0, @m.get
      assert_equal 1, @m.inc

      @m.add(20)
      assert_equal 21, @m.get
      @m.dec
      assert_equal 20, @m.get

      @m.set(100)
      assert_equal 100, @m.get
      @m.sub(11)
      assert_equal 89, @m.get
    end
  end

  sub_test_case 'AliasedGaugeMetric' do
    setup do
      @m = AliasedGaugeMetrics.new
      @m.use_gauge_metric = true
      @m.configure(config_element('metrics', '', {}))
    end

    test 'all aliased gauge operations work well' do
      assert_false @m.has_methods_for_counter
      assert_true @m.has_methods_for_gauge

      assert_equal 0, @m.get
      assert_equal 1, @m.inc

      @m.add(20)
      assert_equal 21, @m.get
      @m.dec
      assert_equal 20, @m.get

      @m.set(100)
      assert_equal 100, @m.get
      @m.sub(11)
      assert_equal 89, @m.get
    end
  end
end