ActionMailbox uses lots of RAM although not in use - how to remove?

dogweather · February 5, 2021, 6:46am

Is there a way to remove ActionMailbox from my Rails app? I’m getting out of memory errors with Rails 6, and derailer shows action_mailbox as the lead memory hog — even though my app doesn’t use it:

TOP: 116.9336 MiB
  rails/all: 62.0156 MiB
    action_mailbox/engine: 35.7305 MiB

sdubois · February 5, 2021, 7:32am

When using rails new --skip-action-mailbox it comments out the line require "action_mailbox/engine" in config/application.rb:

github.com

rails/rails/blob/291a3d2ef29a3842d1156ada7526f4ee60dd2b59/railties/lib/rails/generators/rails/app/templates/config/application.rb.tt#L14


require "rails/all"
<% else -%>
require "rails"
# Pick the frameworks you want:
require "active_model/railtie"
<%= comment_if :skip_active_job %>require "active_job/railtie"
<%= comment_if :skip_active_record %>require "active_record/railtie"
<%= comment_if :skip_active_storage %>require "active_storage/engine"
require "action_controller/railtie"
<%= comment_if :skip_action_mailer %>require "action_mailer/railtie"
<%= comment_if :skip_action_mailbox %>require "action_mailbox/engine"
<%= comment_if :skip_action_text %>require "action_text/engine"
require "action_view/railtie"
<%= comment_if :skip_action_cable %>require "action_cable/engine"
<%= comment_if :skip_sprockets %>require "sprockets/railtie"
<%= comment_if :skip_test %>require "rails/test_unit/railtie"
<% end -%>
# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(*Rails.groups)

So I’d try replacing require "rails/all" with this:

require "active_record/railtie"
require "active_storage/engine"
require "action_controller/railtie"
require "action_view/railtie"
require "action_mailer/railtie"
require "active_job/railtie"
require "action_cable/engine"
# require "action_mailbox/engine"
require "action_text/engine"
require "rails/test_unit/railtie"
require "sprockets/railtie"

dogweather · February 5, 2021, 8:06am

Excellent - great idea.

coorasse · March 17, 2021, 7:12am

I think this is an issue. I love how Rails gives you everything out-of-the-box, but the price to pay to have actionmailbox already included is too high. 30MB loaded in memory is not an irrelevant amount.

strzibny · April 25, 2021, 2:22pm

Yep, this is a solution for skipping it, but does anybody know why Action Mailbox, in particular, takes so much memory?

bensheldon · April 29, 2021, 7:21pm

This knowledge may be out-of-date, but at one point in time, the reason why ActionMailbox uses so much memory is:

ActionMailbox relies upon the Mail gem to parse emails. The Mail gem parses emails by creating several state machines with Ragel, which works by creating big arrays of integers which is the source of the memory usage.

You can dig into this write-up for more info: https://www.schneems.com/2014/11/07/i-ram-what-i-ram.html

And here is some of the work that looks like it wasn’t completed to reduce the memory usage of mail parsing: address_lists_parser.rb requires a lot of memory (~30 mb) · Issue #1342 · mikel/mail · GitHub

nicholaslaws12 · May 8, 2021, 3:41am

We can quickly verify that it does use a lot of memory when there are a lot of Person records being created!

dogweather · September 12, 2021, 4:33am

Update: So far, I’ve found no way to prevent it from being loaded. If anyone has a verified solution — not just a theoretical one — I’d love to hear it.

In the meantime, I’ve gotten my app’s RAM use to easily fit on a 1MB instance by limiting calls to asset helpers.