Add a new option to DelayAgent: emit_interval

This specifies the interval in seconds between emitting events.

The `events_order` option is fixed so that it works without the `max_emitted_events` option.

app/models/agents/delay_agent.rb

@@ -14,6 +14,8 @@ class DelayAgent < Agent
       `expected_receive_period_in_days` is used to determine if the Agent is working. Set it to the maximum number of days
       that you anticipate passing without this Agent receiving an incoming Event.
 
+      `emit_interval` specifies the interval in seconds between emitting events.  This is zero (no interval) by default.
+
       `max_emitted_events` is used to limit the number of the maximum events which should be created. If you omit this DelayAgent will create events for every event stored in the memory.
 
       # Ordering Events
@@ -23,10 +25,11 @@ class DelayAgent < Agent
 
     def default_options
       {
-        'expected_receive_period_in_days' => '10',
-        'max_events' => '100',
+        'expected_receive_period_in_days' => 10,
+        'max_events' => 100,
         'keep' => 'newest',
         'max_emitted_events' => '',
+        'emit_interval' => 0,
         'events_order' => [],
       }
     end
@@ -35,6 +38,7 @@ def default_options
     form_configurable :max_events, type: :number, html_options: { min: 1 }
     form_configurable :keep, type: :array, values: %w[newest oldest]
     form_configurable :max_emitted_events, type: :number, html_options: { min: 0 }
+    form_configurable :emit_interval, type: :number, html_options: { min: 0, step: 0.001 }
     form_configurable :events_order, type: :json
 
     def validate_options
@@ -56,6 +60,10 @@ def validate_options
           errors.add(:base, "The 'max_emitted_events' option is optional and should be an integer greater than 0")
         end
       end
+
+      unless interpolated['emit_interval'] in nil | 0.. | /\A\d(?:\.\d+)?\z/
+        errors.add(:base, "The 'emit_interval' option should be a non-negative number if set")
+      end
     end
 
     def working?
@@ -77,22 +85,24 @@ def receive(incoming_events)
     end
 
     def check
-      if memory['event_ids'].present?
-        events = received_events.where(id: memory['event_ids']).reorder('events.id asc')
-        if interpolated['max_emitted_events'].present?
-          limit = interpolated['max_emitted_events'].to_i
-          events =
-            if options[SortableEvents::EVENTS_ORDER_KEY].present?
-              sort_events(events).first(limit)
-            else
-              events.limit(limit)
-            end
-        end
+      return if memory['event_ids'].blank?
 
-        events.each do |event|
-          create_event payload: event.payload
-          memory['event_ids'].delete(event.id)
-        end
+      events = received_events.where(id: memory['event_ids']).reorder(:id).to_a
+
+      if interpolated[SortableEvents::EVENTS_ORDER_KEY].present?
+        events = sort_events(events)
+      end
+
+      if interpolated['max_emitted_events'].present?
+        events[interpolated['max_emitted_events'].to_i..] = []
+      end
+
+      interval = (options['emit_interval'].presence&.to_f || 0).clamp(0..)
+
+      events.each_with_index do |event, i|
+        sleep interval unless i.zero?
+        create_event payload: event.payload
+        memory['event_ids'].delete(event.id)
       end
     end
   end

spec/models/agents/delay_agent_spec.rb

@@ -1,25 +1,24 @@
 require 'rails_helper'
 
 describe Agents::DelayAgent do
-  let(:agent) do
-    _agent = Agents::DelayAgent.new(name: 'My DelayAgent')
-    _agent.options = _agent.default_options.merge('max_events' => 2)
-    _agent.user = users(:bob)
-    _agent.sources << agents(:bob_website_agent)
-    _agent.save!
-    _agent
+  let(:agent) {
+    Agents::DelayAgent.create!(
+      name: 'My DelayAgent',
+      user: users(:bob),
+      options: default_options.merge('max_events' => 2),
+      sources: [agents(:bob_website_agent)]
+    )
+  }
+
+  let(:default_options) { Agents::DelayAgent.new.default_options }
+
+  def create_event(value)
+    Event.create!(payload: { value: }, agent: agents(:bob_website_agent))
   end
 
-  def create_event
-    _event = Event.new(payload: { random: rand })
-    _event.agent = agents(:bob_website_agent)
-    _event.save!
-    _event
-  end
-
-  let(:first_event) { create_event }
-  let(:second_event) { create_event }
-  let(:third_event) { create_event }
+  let(:first_event) { create_event("one") }
+  let(:second_event) { create_event("two") }
+  let(:third_event) { create_event("three") }
 
   describe "#working?" do
     it "checks if events have been received within expected receive period" do
@@ -48,6 +47,21 @@ def create_event
       expect(agent).to be_valid
     end
 
+    it "should validate emit_interval" do
+      agent.options.delete('emit_interval')
+      expect(agent).to be_valid
+      agent.options['emit_interval'] = "0"
+      expect(agent).to be_valid
+      agent.options['emit_interval'] = "0.5"
+      expect(agent).to be_valid
+      agent.options['emit_interval'] = 0.5
+      expect(agent).to be_valid
+      agent.options['emit_interval'] = ''
+      expect(agent).not_to be_valid
+      agent.options['emit_interval'] = nil
+      expect(agent).to be_valid
+    end
+
     it "should validate presence of expected_receive_period_in_days" do
       agent.options['expected_receive_period_in_days'] = ""
       expect(agent).not_to be_valid
@@ -98,30 +112,62 @@ def create_event
       agent.receive([first_event, second_event, third_event])
       expect(agent.memory['event_ids']).to eq [second_event.id, third_event.id]
 
+      expect(agent).to receive(:sleep).with(0).once
+
       expect {
         agent.check
       }.to change { agent.events.count }.by(2)
 
-      events = agent.events.reorder('events.id desc')
+      events = agent.events.reorder(id: :desc)
       expect(events.first.payload).to eq third_event.payload
       expect(events.second.payload).to eq second_event.payload
 
       expect(agent.memory['event_ids']).to eq []
     end
 
-    it "re-emits max_emitted_events and clears just them from the memory" do
-      agent.options['max_emitted_events'] = 1
-      agent.receive([first_event, second_event, third_event])
-      expect(agent.memory['event_ids']).to eq [second_event.id, third_event.id]
+    context "with events_order and emit_interval" do
+      before do
+        agent.update!(options: agent.options.merge(
+          'events_order' => ['{{ value }}'],
+          'emit_interval' => 1,
+        ))
+      end
 
-      expect {
-        agent.check
-      }.to change { agent.events.count }.by(1)
+      it "re-emits Events in that order and clears the memory with that interval" do
+        agent.receive([first_event, second_event, third_event])
+        expect(agent.memory['event_ids']).to eq [second_event.id, third_event.id]
+
+        expect(agent).to receive(:sleep).with(1).once
+
+        expect {
+          agent.check
+        }.to change { agent.events.count }.by(2)
+
+        events = agent.events.reorder(id: :desc)
+        expect(events.first.payload).to eq second_event.payload
+        expect(events.second.payload).to eq third_event.payload
+
+        expect(agent.memory['event_ids']).to eq []
+      end
+    end
+
+    context "with max_emitted_events" do
+      before do
+        agent.update!(options: agent.options.merge('max_emitted_events' => 1))
+      end
+
+      it "re-emits max_emitted_events and clears just them from the memory" do
+        agent.receive([first_event, second_event, third_event])
+        expect(agent.memory['event_ids']).to eq [second_event.id, third_event.id]
 
-      events = agent.events.reorder('events.id desc')
-      expect(agent.memory['event_ids']).to eq [third_event.id]
-      expect(events.first.payload).to eq second_event.payload
+        expect {
+          agent.check
+        }.to change { agent.events.count }.by(1)
 
+        events = agent.events.reorder(id: :desc)
+        expect(agent.memory['event_ids']).to eq [third_event.id]
+        expect(events.first.payload).to eq second_event.payload
+      end
     end
   end
 end