attribute difference agent (#1572)

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Lloyd Pick 2016-07-10 00:51:08 +01:00 committed by Andrew Cantino
parent d741bfdc5c
commit 8c0a10fc4b
2 changed files with 242 additions and 0 deletions

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module Agents
class AttributeDifferenceAgent < Agent
cannot_be_scheduled!
description <<-MD
The Attribute Difference Agent receives events and emits a new event with
the difference or change of a specific attribute in comparison to the previous
event received.
`path` specifies the JSON path of the attribute to be used from the event.
`output` specifies the new attribute name that will be created on the original payload
and it will contain the difference or change.
`method` specifies if it should be...
* `percentage_change` eg. Previous value was `160`, new value is `116`. Percentage change is `-27.5`
* `decimal_difference` eg. Previous value was `5.5`, new value is `15.2`. Difference is `9.7`
* `integer_difference` eg. Previous value was `50`, new value is `40`. Difference is `-10`
`decimal_precision` defaults to `3`, but you can override this if you want.
`expected_update_period_in_days` is used to determine if the Agent is working.
The resulting event will be a copy of the received event with the difference
or change added as an extra attribute. If you use the `percentage_change` the
attribute will be formatted as such `{{attribute}}_change`, otherwise it will
be `{{attribute}}_diff`.
All configuration options will be liquid interpolated based on the incoming event.
MD
event_description <<-MD
This will change based on the source event.
MD
def default_options
{
'path' => '.data.rate',
'output' => 'rate_diff',
'method' => 'integer_difference',
'expected_update_period_in_days' => 1
}
end
def validate_options
unless options['path'].present? && options['method'].present? && options['output'].present? && options['expected_update_period_in_days'].present?
errors.add(:base, 'The attribute, method and expected_update_period_in_days fields are all required.')
end
end
def working?
event_created_within?(interpolated['expected_update_period_in_days']) && !recent_error_logs?
end
def receive(incoming_events)
incoming_events.each do |event|
handle(interpolated(event), event)
end
end
private
def handle(opts, event)
opts['decimal_precision'] ||= 3
attribute_value = Utils.value_at(event.payload, opts['path'])
attribute_value = attribute_value.nil? ? 0 : attribute_value
payload = event.payload.deep_dup
if opts['method'] == 'percentage_change'
change = calculate_percentage_change(attribute_value, opts['decimal_precision'])
payload[opts['output']] = change
elsif opts['method'] == 'decimal_difference'
difference = calculate_decimal_difference(attribute_value, opts['decimal_precision'])
payload[opts['output']] = difference
elsif opts['method'] == 'integer_difference'
difference = calculate_integer_difference(attribute_value)
payload[opts['output']] = difference
end
created_event = create_event(payload: payload)
log('Propagating new event', outbound_event: created_event, inbound_event: event)
update_memory(attribute_value)
end
def calculate_integer_difference(new_value)
return 0 if last_value.nil?
(new_value.to_i - last_value.to_i)
end
def calculate_decimal_difference(new_value, dec_pre)
return 0.0 if last_value.nil?
(new_value.to_f - last_value.to_f).round(dec_pre.to_i)
end
def calculate_percentage_change(new_value, dec_pre)
return 0.0 if last_value.nil?
(((new_value.to_f / last_value.to_f) * 100) - 100).round(dec_pre.to_i)
end
def last_value
memory['last_value']
end
def update_memory(new_value)
memory['last_value'] = new_value
end
end
end

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require 'rails_helper'
describe Agents::AttributeDifferenceAgent do
def create_event(value=nil)
event = Event.new
event.agent = agents(:jane_weather_agent)
event.payload = {
rate: value
}
event.save!
event
end
before do
@valid_params = {
path: 'rate',
output: 'rate_diff',
method: 'integer_difference',
expected_update_period_in_days: '1'
}
@checker = Agents::AttributeDifferenceAgent.new(name: 'somename', options: @valid_params)
@checker.user = users(:jane)
@checker.save!
end
describe 'validation' do
before do
expect(@checker).to be_valid
end
it 'should validate presence of output' do
@checker.options[:output] = nil
expect(@checker).not_to be_valid
end
it 'should validate presence of path' do
@checker.options[:path] = nil
expect(@checker).not_to be_valid
end
it 'should validate presence of method' do
@checker.options[:method] = nil
expect(@checker).not_to be_valid
end
it 'should validate presence of expected_update_period_in_days' do
@checker.options[:expected_update_period_in_days] = nil
expect(@checker).not_to be_valid
end
end
describe '#working?' do
before :each do
# Need to create an event otherwise event_created_within? returns nil
event = create_event
@checker.receive([event])
end
it 'is when event created within :expected_update_period_in_days' do
@checker.options[:expected_update_period_in_days] = 2
expect(@checker).to be_working
end
it 'isnt when event created outside :expected_update_period_in_days' do
@checker.options[:expected_update_period_in_days] = 2
time_travel_to 2.days.from_now do
expect(@checker).not_to be_working
end
end
end
describe '#receive' do
before :each do
@event = create_event('5.5')
end
it 'creates events when memory is empty' do
expect {
@checker.receive([@event])
}.to change(Event, :count).by(1)
expect(Event.last.payload[:rate_diff]).to eq(0)
end
it 'creates event with extra attribute for integer_difference' do
@checker.receive([@event])
event = create_event('6.5')
expect {
@checker.receive([event])
}.to change(Event, :count).by(1)
expect(Event.last.payload[:rate_diff]).to eq(1)
end
it 'creates event with extra attribute for decimal_difference' do
@checker.options[:method] = 'decimal_difference'
@checker.receive([@event])
event = create_event('6.4')
expect {
@checker.receive([event])
}.to change(Event, :count).by(1)
expect(Event.last.payload[:rate_diff]).to eq(0.9)
end
it 'creates event with extra attribute for percentage_change' do
@checker.options[:method] = 'percentage_change'
@checker.receive([@event])
event = create_event('9')
expect {
@checker.receive([event])
}.to change(Event, :count).by(1)
expect(Event.last.payload[:rate_diff]).to eq(63.636)
end
it 'creates event with extra attribute for percentage_change with the correct rounding' do
@checker.options[:method] = 'percentage_change'
@checker.options[:decimal_precision] = 5
@checker.receive([@event])
event = create_event('9')
expect {
@checker.receive([event])
}.to change(Event, :count).by(1)
expect(Event.last.payload[:rate_diff]).to eq(63.63636)
end
end
end