Problem changing locale with multiple threads

[michelboaventura]

Hi,

I'm having a problem with I18n and multiple threads on a pure ruby app, which can be reproduced with this small script:

require 'i18n'

I18n.available_locales = [:pt, :en]
I18n.enforce_available_locales = true

t1 = Thread.new do
  1.upto(4) do
    puts I18n.t(:foo)
    sleep 1
  end
end

sleep 1 #<<<THIS

I18n.default_locale = :pt
I18n.locale = :pt

t1.join

The problem is: If I run this, I got as output four translation missing: en.foo, but if I remove the sleep marked on the code, I got four translation missing: pt.foo.

I'm aware that the four messages for the pt make sense, since the locale change happens before the thread runs, but I think that on the first case it should print some messages on en and some on pt (the amount of each would be not deterministic).

This is a expected behavior?

[carlosantoniodasilva]

I'll try to verify your script and the issue tomorrow. Thanks for reporting.

[michelboaventura]

Thank you Carlos,

I forgot to mention, this happens on master too and my ruby is:

ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-linux]

[arthurnn]

As far as I can tell , default_locale is not thread safe https://github.com/tjgfernandes/i18n/blob/master/lib/i18n/config.rb#L35 so changing it in one thread, would affect the others. I guess this is done by design.

[michelboaventura]

On this same file, the comment on lines 5 and 6 says that :locale is the only config scoped to a specific thread, so I assumed that default_locale is a global, and all threads should respect it.

If this is by design, we should think a way to change locale to every single thread. This is useful on a GUI software which has several threads running and a user changes the default locale.

[boazsegev]

The issue is still unresolved.

The source of the issue, as it seems from my testing, is that I18n stores the settings in the thread's variable using: Thread.current[:i18n_config].

As you can see in the source code, the settings are persistent. The default_locale isn't reviewed again after it had been reviewed for the first time.

The solution would probably be to change the I18n::Config class's #locale method to keep accessing the default_locale (replacing the ||= with ||), like so:

@locale || default_locale

An easy workaround is to manually reset the locale to the default locale each time.

Here is the code I used for testing:

require 'i18n'

I18n.available_locales = [:pt, :en]
I18n.enforce_available_locales = true
I18n.default_locale = :en

# t1 = Thread.new do
#   1.upto(4) do
#     Thread.current[:i18n_config] = nil
#     puts I18n.t(:foo)
#     puts Thread.current.keys
#     sleep 1
#   end
# end

t1 = Thread.new do
  1.upto(4) do
    I18n.locale = I18n.default_locale
    puts I18n.t(:foo)
    sleep 1
  end
end

sleep 0.1 #<<<THIS

I18n.default_locale = :pt

t1.join

[radar]

I've added the fix from #320 to master now, which should fix this issue. Thanks everyone!