fix: throttle stalecontacts job (#11430)

- throttle stale contacts job
- process 20% accounts every day
- reduce batch size from 100 to 20
- add delay between jobs

app/jobs/internal/process_stale_contacts_job.rb

@@ -1,5 +1,5 @@
 # housekeeping
-# remove stale contacts for all accounts
+# remove stale contacts for subset of accounts each day
 # - have no identification (email, phone_number, and identifier are NULL)
 # - have no conversations
 # - are older than 30 days
@@ -7,14 +7,33 @@
 class Internal::ProcessStaleContactsJob < ApplicationJob
   queue_as :housekeeping
 
+  # Number of day-based groups to split accounts into
+  DISTRIBUTION_GROUPS = 5
+  # Max accounts to process in one batch
+  MAX_ACCOUNTS_PER_BATCH = 20
+
+  # Process only a subset of accounts per day to avoid flooding the queue
   def perform
     return unless ChatwootApp.chatwoot_cloud?
 
-    Account.find_in_batches(batch_size: 100) do |accounts|
-      accounts.each do |account|
-        Rails.logger.info "Enqueuing RemoveStaleContactsJob for account #{account.id}"
-        Internal::RemoveStaleContactsJob.perform_later(account)
-      end
+    # Use the day of the month to determine which accounts to process
+    day_of_month = Date.current.day
+    remainder = day_of_month % DISTRIBUTION_GROUPS
+
+    # Count total accounts for logging
+    total_accounts = Account.count
+    log_message = "ProcessStaleContactsJob: Processing accounts with ID % #{DISTRIBUTION_GROUPS} = "
+    log_message += "#{remainder} (out of #{total_accounts} total accounts)"
+    Rails.logger.info log_message
+
+    # Process only accounts where ID % 5 = remainder for today
+    # This ensures each account is processed approximately once every 5 days
+    Account.where("id % #{DISTRIBUTION_GROUPS} = ?", remainder).find_each(batch_size: MAX_ACCOUNTS_PER_BATCH) do |account|
+      Rails.logger.info "Enqueuing RemoveStaleContactsJob for account #{account.id}"
+
+      # Add a small delay between jobs to further reduce queue pressure
+      delay = rand(1..10).minutes
+      Internal::RemoveStaleContactsJob.set(wait: delay).perform_later(account)
     end
   end
 end