ruby: Prevent concurrent usage of Trilogy connections

contrib/ruby/lib/trilogy.rb

@@ -7,7 +7,27 @@
 require "trilogy/encoding"
 
 class Trilogy
+  Synchronization = Module.new
+
+  source = public_instance_methods(false).map do |method|
+    <<~RUBY
+      def #{method}(...)
+        raise SynchronizationError unless @mutex.try_lock
+
+        begin
+          super
+        ensure
+          @mutex.unlock
+        end
+      end
+    RUBY
+  end
+  Synchronization.class_eval(source.join(";"))
+
+  prepend(Synchronization)
+
   def initialize(options = {})
+    @mutex = Mutex.new
     options[:port] = options[:port].to_i if options[:port]
     mysql_encoding = options[:encoding] || "utf8mb4"
     encoding = Trilogy::Encoding.find(mysql_encoding)

contrib/ruby/lib/trilogy/error.rb

@@ -54,6 +54,12 @@ class BaseConnectionError < BaseError
     include ConnectionError
   end
 
+  class SynchronizationError < BaseError
+    def initialize(message = "This connection is already in use by another thread or fiber")
+      super
+    end
+  end
+
   # Trilogy::ClientError is the base error type for invalid queries or parameters
   # that shouldn't be retried.
   class ClientError < BaseError

contrib/ruby/test/client_test.rb

@@ -705,6 +705,17 @@ def test_releases_gvl
     end
   end
 
+  def test_prevent_concurrent_use
+    client = new_tcp_client
+    thread = Thread.new { client.query("SELECT SLEEP(1)") }
+    thread.join(0.2)
+    assert_raises Trilogy::SynchronizationError do
+      client.query("SELECT 1")
+    end
+    thread.join
+    client.close
+  end
+
   USR1 = Class.new(StandardError)
 
   def test_interruptible_when_releasing_gvl