fix: exponential backoff before prompting reauthorization

app/jobs/inboxes/fetch_imap_emails_job.rb

@@ -6,26 +6,30 @@ class Inboxes::FetchImapEmailsJob < MutexApplicationJob
   def perform(channel, interval = 1)
     return unless should_fetch_email?(channel)
 
-    key = format(::Redis::Alfred::EMAIL_MESSAGE_MUTEX, inbox_id: channel.inbox.id)
-
-    with_lock(key, 5.minutes) do
-      process_email_for_channel(channel, interval)
-    end
-  rescue *ExceptionList::IMAP_EXCEPTIONS => e
-    Rails.logger.error "Authorization error for email channel - #{channel.inbox.id} : #{e.message}"
-  rescue EOFError, OpenSSL::SSL::SSLError, Net::IMAP::NoResponseError, Net::IMAP::BadResponseError, Net::IMAP::InvalidResponseError,
-         Net::IMAP::ResponseParseError, Net::IMAP::ResponseReadError, Net::IMAP::ResponseTooLargeError => e
-    Rails.logger.error "Error for email channel - #{channel.inbox.id} : #{e.message}"
-  rescue LockAcquisitionError
-    Rails.logger.error "Lock failed for #{channel.inbox.id}"
+    fetch_emails_with_backoff(channel, interval)
   rescue StandardError => e
     ChatwootExceptionTracker.new(e, account: channel.account).capture_exception
   end
 
   private
 
+  def fetch_emails_with_backoff(channel, interval)
+    key = format(::Redis::Alfred::EMAIL_MESSAGE_MUTEX, inbox_id: channel.inbox.id)
+    with_lock(key, 5.minutes) { process_email_for_channel(channel, interval) }
+    channel.clear_imap_backoff!
+  rescue *ExceptionList::IMAP_EXCEPTIONS => e
+    Rails.logger.error "Authorization error for email channel - #{channel.inbox.id} : #{e.message}"
+    channel.apply_imap_backoff!
+  rescue EOFError, OpenSSL::SSL::SSLError, Net::IMAP::NoResponseError, Net::IMAP::BadResponseError, Net::IMAP::InvalidResponseError,
+         Net::IMAP::ResponseParseError, Net::IMAP::ResponseReadError, Net::IMAP::ResponseTooLargeError => e
+    Rails.logger.error "Error for email channel - #{channel.inbox.id} : #{e.message}"
+    channel.apply_imap_backoff!
+  rescue LockAcquisitionError
+    Rails.logger.error "Lock failed for #{channel.inbox.id}"
+  end
+
   def should_fetch_email?(channel)
-    channel.imap_enabled? && !channel.reauthorization_required?
+    channel.imap_enabled? && !channel.reauthorization_required? && !channel.in_backoff?
   end
 
   def process_email_for_channel(channel, interval)

app/models/channel/email.rb

@@ -39,6 +39,8 @@ class Channel::Email < ApplicationRecord
   include Reauthorizable
 
   AUTHORIZATION_ERROR_THRESHOLD = 10
+  MAX_IMAP_RETRIES = 5
+  IMAP_BACKOFF_BASE_SECONDS = 60
 
   # TODO: Remove guard once encryption keys become mandatory (target 3-4 releases out).
   if Chatwoot.encryption_configured?
@@ -72,6 +74,27 @@ class Channel::Email < ApplicationRecord
     imap_enabled && imap_address == 'imap.gmail.com'
   end
 
+  def in_backoff?
+    imap_retry_after.present? && imap_retry_after > Time.current
+  end
+
+  def apply_imap_backoff!
+    new_count = imap_retry_count + 1
+    if new_count >= MAX_IMAP_RETRIES
+      update!(imap_retry_count: 0, imap_retry_after: nil)
+      prompt_reauthorization!
+    else
+      backoff_seconds = IMAP_BACKOFF_BASE_SECONDS * (2**new_count)
+      update!(imap_retry_count: new_count, imap_retry_after: backoff_seconds.seconds.from_now)
+    end
+  end
+
+  def clear_imap_backoff!
+    return unless imap_retry_count.positive? || imap_retry_after.present?
+
+    update!(imap_retry_count: 0, imap_retry_after: nil)
+  end
+
   private
 
   def ensure_forward_to_email

db/migrate/20260223100000_add_imap_backoff_to_channel_email.rb

@@ -0,0 +1,6 @@
+class AddImapBackoffToChannelEmail < ActiveRecord::Migration[7.2]
+  def change
+    add_column :channel_email, :imap_retry_count, :integer, default: 0, null: false
+    add_column :channel_email, :imap_retry_after, :datetime
+  end
+end