perf(conversations): throttle agent_last_seen_at updates to reduce DB load (#13355)

High-traffic accounts generate excessive database writes due to agents frequently switching between conversations. The update_last_seen endpoint was being called every time an agent loaded a conversation, resulting in unnecessary updates to agent_last_seen_at and assignee_last_seen_at even when there were no new messages to mark as read. #### Solution Implemented throttling for the update_last_seen endpoint: **Unread messages present:** - Updates immediately without throttling to maintain accurate read/unread state - Uses assignee_unread_messages for assignees, unread_messages for other agents **No unread messages:** - Throttles updates to once per hour per conversation - Checks if agent_last_seen_at is older than 1 hour before updating - For assignees, checks both agent_last_seen_at AND assignee_last_seen_at - updates if either timestamp is old - Skips DB write if all relevant timestamps were updated within the last hour - Consolidated two separate update_column calls into a single update_columns call to reduce DB queries
2026-01-23 22:23:41 -08:00
parent 747d451387
commit ad2329c237
3 changed files with 101 additions and 3 deletions
--- a/app/controllers/api/v1/accounts/conversations_controller.rb
+++ b/app/controllers/api/v1/accounts/conversations_controller.rb
@@ -110,6 +110,15 @@ class Api::V1::Accounts::ConversationsController < Api::V1::Accounts::BaseContro
  end

  def update_last_seen
+    # High-traffic accounts generate excessive DB writes when agents frequently switch between conversations.
+    # Throttle last_seen updates to once per hour when there are no unread messages to reduce DB load.
+    # Always update immediately if there are unread messages to maintain accurate read/unread state.
+    return update_last_seen_on_conversation(DateTime.now.utc, true) if assignee? && @conversation.assignee_unread_messages.any?
+    return update_last_seen_on_conversation(DateTime.now.utc, false) if !assignee? && @conversation.unread_messages.any?
+
+    # No unread messages - apply throttling to limit DB writes
+    return unless should_update_last_seen?
+
    update_last_seen_on_conversation(DateTime.now.utc, assignee?)
  end

@@ -142,12 +151,25 @@ class Api::V1::Accounts::ConversationsController < Api::V1::Accounts::BaseContro
  end

  def update_last_seen_on_conversation(last_seen_at, update_assignee)
+    updates = { agent_last_seen_at: last_seen_at }
+    updates[:assignee_last_seen_at] = last_seen_at if update_assignee.present?
+
    # rubocop:disable Rails/SkipsModelValidations
-    @conversation.update_column(:agent_last_seen_at, last_seen_at)
-    @conversation.update_column(:assignee_last_seen_at, last_seen_at) if update_assignee.present?
+    @conversation.update_columns(updates)
    # rubocop:enable Rails/SkipsModelValidations
  end

+  def should_update_last_seen?
+    # Update if at least one relevant timestamp is older than 1 hour or not set
+    # This prevents redundant DB writes when agents repeatedly view the same conversation
+    agent_needs_update = @conversation.agent_last_seen_at.blank? || @conversation.agent_last_seen_at < 1.hour.ago
+    return agent_needs_update unless assignee?
+
+    # For assignees, check both timestamps - update if either is old
+    assignee_needs_update = @conversation.assignee_last_seen_at.blank? || @conversation.assignee_last_seen_at < 1.hour.ago
+    agent_needs_update || assignee_needs_update
+  end
+
  def set_conversation_status
    @conversation.status = params[:status]
    @conversation.snoozed_until = parse_date_time(params[:snoozed_until].to_s) if params[:snoozed_until]
--- a/app/models/conversation.rb
+++ b/app/models/conversation.rb
@@ -167,6 +167,10 @@ class Conversation < ApplicationRecord
    agent_last_seen_at.present? ? messages.created_since(agent_last_seen_at) : messages
  end

+  def assignee_unread_messages
+    assignee_last_seen_at.present? ? messages.created_since(assignee_last_seen_at) : messages
+  end
+
  def unread_incoming_messages
    unread_messages.where(account_id: account_id).incoming.last(10)
  end
--- a/spec/controllers/api/v1/accounts/conversations_controller_spec.rb
+++ b/spec/controllers/api/v1/accounts/conversations_controller_spec.rb
@@ -667,6 +667,8 @@ RSpec.describe 'Conversations API', type: :request do
      end

      it 'updates last seen' do
+        conversation.update!(agent_last_seen_at: nil)
+
        post "/api/v1/accounts/#{account.id}/conversations/#{conversation.display_id}/update_last_seen",
             headers: agent.create_new_auth_token,
             as: :json
@@ -676,7 +678,7 @@ RSpec.describe 'Conversations API', type: :request do
      end

      it 'updates assignee last seen' do
-        conversation.update!(assignee_id: agent.id)
+        conversation.update!(assignee_id: agent.id, agent_last_seen_at: nil)

        expect(conversation.reload.assignee_last_seen_at).to be_nil

@@ -687,6 +689,76 @@ RSpec.describe 'Conversations API', type: :request do
        expect(response).to have_http_status(:success)
        expect(conversation.reload.assignee_last_seen_at).not_to be_nil
      end
+
+      it 'throttles updates within an hour when there are no unread messages' do
+        conversation.update!(agent_last_seen_at: 30.minutes.ago)
+        # Ensure all messages are older than agent_last_seen_at (no unread messages)
+        # rubocop:disable Rails/SkipsModelValidations
+        conversation.messages.update_all(created_at: 1.hour.ago)
+        # rubocop:enable Rails/SkipsModelValidations
+        initial_last_seen = conversation.agent_last_seen_at
+
+        post "/api/v1/accounts/#{account.id}/conversations/#{conversation.display_id}/update_last_seen",
+             headers: agent.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(conversation.reload.agent_last_seen_at).to be_within(1.second).of(initial_last_seen)
+      end
+
+      it 'updates even within an hour when there are unread messages' do
+        conversation.update!(agent_last_seen_at: 30.minutes.ago)
+        # Create a new message after agent_last_seen_at (unread message)
+        create(:message, conversation: conversation, created_at: 5.minutes.ago)
+        initial_last_seen = conversation.agent_last_seen_at
+
+        post "/api/v1/accounts/#{account.id}/conversations/#{conversation.display_id}/update_last_seen",
+             headers: agent.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:success)
+        expect(conversation.reload.agent_last_seen_at).not_to be_within(1.second).of(initial_last_seen)
+        expect(conversation.reload.agent_last_seen_at).to be > initial_last_seen
+      end
+
+      it 'updates both if one timestamp is old even when the other is recent' do
+        conversation.update!(assignee_id: agent.id, agent_last_seen_at: 2.hours.ago, assignee_last_seen_at: 30.minutes.ago)
+        # Ensure all messages are older than assignee_last_seen_at (no unread messages)
+        # rubocop:disable Rails/SkipsModelValidations
+        conversation.messages.update_all(created_at: 1.hour.ago)
+        # rubocop:enable Rails/SkipsModelValidations
+
+        initial_agent_last_seen = conversation.agent_last_seen_at
+
+        post "/api/v1/accounts/#{account.id}/conversations/#{conversation.display_id}/update_last_seen",
+             headers: agent.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:success)
+        # Both should be updated because agent_last_seen_at is old
+        expect(conversation.reload.agent_last_seen_at).to be > initial_agent_last_seen
+        expect(conversation.reload.assignee_last_seen_at).to be > initial_agent_last_seen
+      end
+
+      it 'throttles only when both timestamps are recent and no unread messages' do
+        conversation.update!(assignee_id: agent.id, agent_last_seen_at: 30.minutes.ago, assignee_last_seen_at: 30.minutes.ago)
+        # Ensure all messages are older (no unread messages)
+        # rubocop:disable Rails/SkipsModelValidations
+        conversation.messages.update_all(created_at: 1.hour.ago)
+        # rubocop:enable Rails/SkipsModelValidations
+
+        initial_agent_last_seen = conversation.agent_last_seen_at
+        initial_assignee_last_seen = conversation.assignee_last_seen_at
+
+        post "/api/v1/accounts/#{account.id}/conversations/#{conversation.display_id}/update_last_seen",
+             headers: agent.create_new_auth_token,
+             as: :json
+
+        expect(response).to have_http_status(:success)
+        # Both should remain unchanged (throttled)
+        expect(conversation.reload.agent_last_seen_at).to be_within(1.second).of(initial_agent_last_seen)
+        expect(conversation.reload.assignee_last_seen_at).to be_within(1.second).of(initial_assignee_last_seen)
+      end
    end
  end