From 4058a9143e5f45611fc4cc852b378f9f6fb6d34f Mon Sep 17 00:00:00 2001
From: TienTT <tien.tt@holistics.io>
Date: Thu, 14 Nov 2024 16:42:35 +0700
Subject: [PATCH] fix(context): do not modify stack array directly when attach
 and detach

---
 api/lib/opentelemetry/context.rb       |  7 ++--
 api/test/opentelemetry/context_test.rb | 55 ++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 3 deletions(-)

diff --git a/api/lib/opentelemetry/context.rb b/api/lib/opentelemetry/context.rb
index 05e96ed6b..f6f9d3d95 100644
--- a/api/lib/opentelemetry/context.rb
+++ b/api/lib/opentelemetry/context.rb
@@ -41,8 +41,9 @@ def current
       # @return [Object] A token to be used when detaching
       def attach(context)
         s = stack
-        s.push(context)
-        s.size
+        new_stack = s + [context]
+        Thread.current[STACK_KEY] = new_stack
+        new_stack.size
       end
 
       # Restores the previous Context associated with the current Fiber.
@@ -57,7 +58,7 @@ def detach(token)
         calls_matched = (token == s.size)
         OpenTelemetry.handle_error(exception: DetachError.new('calls to detach should match corresponding calls to attach.')) unless calls_matched
 
-        s.pop
+        Thread.current[STACK_KEY] = s[...-1] || []
         calls_matched
       end
 
diff --git a/api/test/opentelemetry/context_test.rb b/api/test/opentelemetry/context_test.rb
index eb91a907b..a85a85787 100644
--- a/api/test/opentelemetry/context_test.rb
+++ b/api/test/opentelemetry/context_test.rb
@@ -331,5 +331,60 @@
         _(Context.current[bar_key]).must_be_nil
       end
     end
+
+    describe 'when current thread local variable get copied to new thread' do
+      # NOTE: this is the similar behavior of ActionController::Live as identified in open-telemetry/opentelemetry-ruby-contrib#772
+      it 'attach and detach in child thread will not affect parent thread' do
+        OpenTelemetry::TestHelpers.with_test_logger do |log_stream|
+          ctx = new_context
+
+          t1 = Thread.current
+          locals = t1.keys.map { |key| [key, t1[key]] }
+
+          done_attach_new_context = false
+
+          token1 = Context.attach(ctx)
+          Thread.new do
+            t2 = Thread.current
+            locals.each { |k, v| t2[k] = v }
+
+            Context.attach(ctx)
+            done_attach_new_context = true
+          end
+
+          until done_attach_new_context; end
+
+          Context.detach(token1)
+
+          _(log_stream.string).wont_match(/OpenTelemetry error: calls to detach should match corresponding calls to attach/)
+        end
+      end
+
+      it 'clear in child thread will not affect parent thread' do
+        OpenTelemetry::TestHelpers.with_test_logger do |log_stream|
+          ctx = new_context
+
+          t1 = Thread.current
+          locals = t1.keys.map { |key| [key, t1[key]] }
+
+          done_clear_context = false
+
+          token1 = Context.attach(ctx)
+          Thread.new do
+            t2 = Thread.current
+            locals.each { |k, v| t2[k] = v }
+
+            Context.clear
+            done_clear_context = true
+          end
+
+          until done_clear_context; end
+
+          Context.detach(token1)
+
+          _(log_stream.string).wont_match(/OpenTelemetry error: calls to detach should match corresponding calls to attach/)
+        end
+      end
+    end
   end
 end