From 6aecb58a34283f58f40cfb05e2245c55e0439190 Mon Sep 17 00:00:00 2001
From: Zsolt Kozaroczy <kiskoza@gmail.com>
Date: Sat, 13 Aug 2022 23:36:50 +0200
Subject: [PATCH] Thread safety (#2520)

* Make Config.locale and Config.random thread safe

* Make UniqueGenerator thread safe
---
 lib/faker.rb                                  | 17 ++++----
 lib/helpers/unique_generator.rb               | 24 ++++++------
 .../default/test_faker_unique_generator.rb    | 39 +++++++++++++++++++
 test/test_determinism.rb                      | 20 ++++++++++
 4 files changed, 82 insertions(+), 18 deletions(-)

diff --git a/lib/faker.rb b/lib/faker.rb
index eb0b30f7fe..47f6df1369 100644
--- a/lib/faker.rb
+++ b/lib/faker.rb
@@ -13,23 +13,26 @@
 
 module Faker
   module Config
-    @locale = nil
-    @random = nil
-
     class << self
-      attr_writer :locale, :random
+      def locale=(new_locale)
+        Thread.current[:faker_config_locale] = new_locale
+      end
 
       def locale
         # Because I18n.locale defaults to :en, if we don't have :en in our available_locales, errors will happen
-        @locale || (I18n.available_locales.include?(I18n.locale) ? I18n.locale : I18n.available_locales.first)
+        Thread.current[:faker_config_locale] || (I18n.available_locales.include?(I18n.locale) ? I18n.locale : I18n.available_locales.first)
       end
 
       def own_locale
-        @locale
+        Thread.current[:faker_config_locale]
+      end
+
+      def random=(new_random)
+        Thread.current[:faker_config_random] = new_random
       end
 
       def random
-        @random || Random
+        Thread.current[:faker_config_random] || Random
       end
     end
   end
diff --git a/lib/helpers/unique_generator.rb b/lib/helpers/unique_generator.rb
index 21f375d679..b6115671ff 100644
--- a/lib/helpers/unique_generator.rb
+++ b/lib/helpers/unique_generator.rb
@@ -2,16 +2,9 @@
 
 module Faker
   class UniqueGenerator
-    @marked_unique = Set.new # Holds names of generators with unique values
-
-    class << self
-      attr_reader :marked_unique
-    end
-
     def initialize(generator, max_retries)
       @generator = generator
       @max_retries = max_retries
-      @previous_results = Hash.new { |hash, key| hash[key] = Set.new }
     end
 
     def method_missing(name, *arguments)
@@ -20,9 +13,9 @@ def method_missing(name, *arguments)
       @max_retries.times do
         result = @generator.public_send(name, *arguments)
 
-        next if @previous_results[[name, arguments]].include?(result)
+        next if previous_results[[name, arguments]].include?(result)
 
-        @previous_results[[name, arguments]] << result
+        previous_results[[name, arguments]] << result
         return result
       end
 
@@ -39,8 +32,17 @@ def respond_to_missing?(method_name, include_private = false)
 
     RetryLimitExceeded = Class.new(StandardError)
 
+    def previous_results
+      Thread.current[:faker_unique_generator_previous_results] ||= {}
+      Thread.current[:faker_unique_generator_previous_results][@generator] ||= Hash.new { |hash, key| hash[key] = Set.new }
+    end
+
     def clear
-      @previous_results.clear
+      previous_results.clear
+    end
+
+    def self.marked_unique
+      Thread.current[:faker_unique_generator_marked_unique] ||= Set.new
     end
 
     def self.clear
@@ -51,7 +53,7 @@ def self.clear
     def exclude(name, arguments, values)
       values ||= []
       values.each do |value|
-        @previous_results[[name, arguments]] << value
+        previous_results[[name, arguments]] << value
       end
     end
   end
diff --git a/test/faker/default/test_faker_unique_generator.rb b/test/faker/default/test_faker_unique_generator.rb
index 4f0f7e4765..c87d1319f8 100644
--- a/test/faker/default/test_faker_unique_generator.rb
+++ b/test/faker/default/test_faker_unique_generator.rb
@@ -121,4 +121,43 @@ def stubbed_generator2.test
       assert_equal(2, generator2.test)
     end
   end
+
+  def test_thread_safety
+    stubbed_generator = Object.new
+    def stubbed_generator.test
+      1
+    end
+
+    generator = Faker::UniqueGenerator.new(stubbed_generator, 3)
+
+    Thread.new do
+      assert_equal(1, generator.test)
+
+      assert_raises Faker::UniqueGenerator::RetryLimitExceeded do
+        generator.test
+      end
+    end.join
+
+    Thread.new do
+      assert_equal(1, generator.test)
+    end.join
+
+    assert_equal(1, generator.test)
+
+    assert_raises Faker::UniqueGenerator::RetryLimitExceeded do
+      generator.test
+    end
+
+    Thread.new do
+      generator.clear
+    end.join
+
+    assert_raises Faker::UniqueGenerator::RetryLimitExceeded do
+      generator.test
+    end
+
+    generator.clear
+
+    assert_equal(1, generator.test)
+  end
 end
diff --git a/test/test_determinism.rb b/test/test_determinism.rb
index d106f33473..120140dd46 100644
--- a/test/test_determinism.rb
+++ b/test/test_determinism.rb
@@ -22,6 +22,26 @@ def test_determinism
     end
   end
 
+  def test_thread_safety
+    expected_values = 2.times.map do |index|
+      Faker::Config.random = Random.new(index)
+      Faker::Number.digit
+    end
+
+    threads = expected_values.each_with_index.map do |expected_value, index|
+      Thread.new do
+        100_000.times.each do
+          Faker::Config.random = Random.new(index)
+          output = Faker::Number.digit
+
+          assert_equal output, expected_value
+        end
+      end
+    end
+
+    threads.each(&:join)
+  end
+
   private
 
   def deterministic_random?(first, method_name)