Unable to save backup file. Exception thrown Errno::ENOENT

[skcc321]

Describe the bug

Hi there, I face some issues when I use puma in clustered mode (following the documentation in readme)
But I would list here a bit more issues:

• If I want multiple clients (multi-process app on a single machine - puma clustered mode for instance) - all processes have the same backup_file https://github.com/Unleash/unleash-client-ruby/blob/main/lib/unleash/configuration.rb#L47, only if you name application differently I can get separated backup_file so I won’t face with no such file or dir error.
  This error comes from there on File.rename. The only mechanism you use is Mutex, but it does not work for multiple processes (only for threads inside a single process)
• second issue - https://github.com/Unleash/unleash-client-ruby/blob/c745ed4569b5e83498d22e0fbf618e8eb6ce2002/README.md#list-of-arguments
  backup_file is overwritten [always](https://github.com/Unleash/unleash-client-ruby/blob/main/lib/unleash/client.rb#L15, https://github.com/Unleash/unleash-client-ruby/blob/main/lib/unleash/configuration.rb#L32), so I cannot define it explicitly.
• another kinda issue - I need to control shutdown to avoid loss of data on my own, so the lib does not catch any termination signals.
  we have puma in clustered mode on prod and in a single-mode in dev, which means I cannot use the same config on both ENVs according to the configuration section on the readme.
• also would be great to have some prepared stubs for testing frameworks like RSpec.

Steps to reproduce the bug

system: MacOS BigSur 11.4

setup unleash according to the readme for puma (clustered mode) https://github.com/Unleash/unleash-client-ruby/blob/c745ed4569b5e83498d22e0fbf618e8eb6ce2002/README.md#with-preload_app

• initializer & puma.rb hook.
  bundle exec puma -w 3 --preload

Expected behavior

No errors should be thrown.

Logs, error output, etc.

...
[2022-06-07T12:06:38.866649+02:00          Unleash ERROR] : Unable to save backup file. Exception thrown Errno::ENOENT:'No such file or directory @ rb_file_s_rename - (/var/folders/pf/_39szp0x68v6s0vrr0jfz9l80000gn/T/unlea
sh-oh-backend-repo.json.tmp, /var/folders/pf/_39szp0x68v6s0vrr0jfz9l80000gn/T/unleash-oh-backend-repo.json)'                                                                                                                  
[2022-06-07T12:06:38.867553+02:00          Unleash ERROR] : stacktrace: ["/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/unleash-4.2.1/lib/unleash/toggle_fetcher.rb:76:in `rename'", "/Users/viktorsych/.rb
env/versions/3.0.2/lib/ruby/gems/3.0.0/gems/unleash-4.2.1/lib/unleash/toggle_fetcher.rb:76:in `block in save!'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/unleash-4.2.1/lib/unleash/toggle_fetcher.rb
:72:in `synchronize'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/unleash-4.2.1/lib/unleash/toggle_fetcher.rb:72:in `save!'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/unleash
-4.2.1/lib/unleash/toggle_fetcher.rb:63:in `fetch'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/unleash-4.2.1/lib/unleash/toggle_fetcher.rb:22:in `initialize'", "/Users/viktorsych/.rbenv/versions/3.0
.2/lib/ruby/gems/3.0.0/gems/unleash-4.2.1/lib/unleash/client.rb:21:in `new'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/unleash-4.2.1/lib/unleash/client.rb:21:in `initialize'", "/Users/viktorsych/Co
de/oh/overhaul-backend/lib/unleash.rb:19:in `new'", "/Users/viktorsych/Code/oh/overhaul-backend/lib/unleash.rb:19:in `preload'", "config/puma.rb:56:in `block in _load_from'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ru
by/gems/3.0.0/gems/puma-5.6.4/lib/puma/configuration.rb:297:in `block in run_hooks'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.4/lib/puma/configuration.rb:295:in `each'", "/Users/viktorsyc
h/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.4/lib/puma/configuration.rb:295:in `run_hooks'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.4/lib/puma/cluster/worker.rb:55:in `run'
", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.4/lib/puma/cluster.rb:204:in `worker'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.4/lib/puma/cluster.rb:97:in `
block in spawn_worker'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/activesupport-6.1.5/lib/active_support/fork_tracker.rb:10:in `block in fork'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/ge
ms/3.0.0/gems/activesupport-6.1.5/lib/active_support/fork_tracker.rb:10:in `block in fork'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/activesupport-6.1.5/lib/active_support/fork_tracker.rb:8:in `fo
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, "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.4/lib/puma/cluster.rb:79:in `block in spawn_workers'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.4/lib/puma/clus
ter.rb:72:in `times'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.4/lib/puma/cluster.rb:72:in `spawn_workers'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.4/l
ib/puma/cluster.rb:415:in `run'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.4/lib/puma/launcher.rb:182:in `run'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.
4/lib/puma/cli.rb:81:in `run'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/puma-5.6.4/bin/puma:10:in `<top (required)>'", "/Users/viktorsych/.rbenv/versions/3.0.2/bin/puma:23:in `load'", "/Users/vikt
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sych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/bundler-2.2.32/lib/bundler/vendor/thor/lib/thor/base.rb:485:in `start'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/bundler-2.2.32/lib/bundler/cli.
rb:25:in `start'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/bundler-2.2.32/exe/bundle:49:in `block in <top (required)>'", "/Users/viktorsych/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/bundler-2
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/3.0.2/bin/bundle:23:in `load'", "/Users/viktorsych/.rbenv/versions/3.0.2/bin/bundle:23:in `<main>'"]

Screenshots

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Additional context

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Unleash version

4.2.1

Subscription type

No response

Hosting type

No response

SDK information (language and version)

ruby, RoR, Sidekiq, Puma

[skcc321]

Just to make everything work for puma clustered/single modes, sidekiq, rails console & other libs I did next config like a workaround:

in lib/unleash.rb

# frozen_string_literal: true

require "unleash"
require "socket"
require "securerandom"
require "forwardable"

module UNLEASH
  FakeClient = Struct.new(:turn_on) do
    def enabled?(*)
      turn_on
    end

    def if_enabled(*)
      yield if turn_on
    end

    def shutdown; end
    def shutdown!; end
  end

  class << self
    extend Forwardable

    def_delegators :client,
      :enabled?,
      :if_enabled,
      :get_variant,
      :shutdown,
      :shutdown!

    def preload
      @client = if ENV.fetch("UNLEASH_TOKEN", nil) && ENV.fetch("UNLEASH_URL", nil)
        Unleash::Client.new(
          app_name: "#{ENV.fetch("DD_SERVICE", nil)}-#{SecureRandom.uuid}",
          environment: ENV.fetch("DD_ENV", nil),
          instance_id: Socket.gethostname,
          url: ENV.fetch("UNLEASH_URL", nil),
          custom_http_headers: { Authorization: ENV.fetch("UNLEASH_TOKEN", nil) }
        )
      else
        FakeClient.new(false)
      end
    end

    def client
      @client || preload
    end
  end
end

in puma.rb

require_relative File.expand_path("../lib/unleash.rb", __dir__) # if not --preload

# unleash
on_worker_boot do
  UNLEASH.preload
end

on_worker_shutdown do
  UNLEASH.shutdown
end

in config/initializers/unleash.rb

require_relative File.expand_path("../../lib/unleash.rb", __dir__)

Rails.application.console do
  UNLEASH.preload
end

Sidekiq.configure_server do |config|
  config.on(:startup) do
    UNLEASH.preload
  end

  config.on(:shutdown) do
    UNLEASH.shutdown
  end
end

So now I can call UNLEASH.enabled?("some feature") in any place, and it will work (Unleash::Client will be initialized in a lazy way).
In puma, sidekiq, rails c I do preload the client to avoid some delay on the initial call.
in RSpec it is disabled by default because my test env does not have credentials ENV vars. I can allow(UNLEASH).to receive(:enabled?).with("some feature").and_return(true) if I want to make sure the test works well with enabled/disabled feature.

[skcc321]

But such configuration looks awful, so would be great to find some more convenient way of unleash client configuration.

[atraastrum]

I also faced same issue with Unicorn server. Worker processes use same file for backup and throw error as posted by creator of this issue. The potential workaround is to set different backup file for each worker process:

after_worker_ready do |server, worker|
  app_name = Unleash.configuration.app_name
  Unleash.configuration.backup_file = Dir.tmpdir + "/unleash-#{app_name}-#{worker.nr}-repo.json"
  ::UNLEASH = Unleash::Client.new
end

[ganey]

I also faced same issue with Unicorn server. Worker processes use same file for backup and throw error as posted by creator of this issue. The potential workaround is to set different backup file for each worker process:

after_worker_ready do |server, worker|
  app_name = Unleash.configuration.app_name
  Unleash.configuration.backup_file = Dir.tmpdir + "/unleash-#{app_name}-#{worker.nr}-repo.json"
  ::UNLEASH = Unleash::Client.new
end

Thanks for this, I've also got it working in the worker boot block

on_worker_boot do |index|
  Unleash.configuration.backup_file = Dir.tmpdir + "/unleash-#{index}-repo.json"
  Rails.configuration.unleash = Unleash::Client.new
end