Add .duplicate transaction method

Implement support for the `appsignal_transaction_duplicate` method
implemented in the agent side the extension, in both the Ruby C
extension and the JRuby FFI extension.

Implement a `duplicate` method for the `Transaction` class that
calls the extension's own `duplicate` method to duplicate a
transaction.

ext/appsignal_extension.c

@@ -273,6 +273,30 @@ static VALUE finish_transaction(VALUE self, VALUE gc_duration_ms) {
   return sample == 1 ? Qtrue : Qfalse;
 }
 
+static VALUE duplicate_transaction(VALUE self, VALUE new_transaction_id) {
+  appsignal_transaction_t* transaction;
+  appsignal_transaction_t* duplicate_transaction;
+
+  Check_Type(new_transaction_id, T_STRING);
+  Data_Get_Struct(self, appsignal_transaction_t, transaction);
+
+  duplicate_transaction = appsignal_duplicate_transaction(
+      transaction,
+      make_appsignal_string(new_transaction_id)
+  );
+
+  if (duplicate_transaction) {
+      return Data_Wrap_Struct(
+          Transaction,
+          NULL,
+          appsignal_free_transaction,
+          duplicate_transaction
+      );
+  } else {
+      return Qnil;
+  }
+}
+
 static VALUE complete_transaction(VALUE self) {
   appsignal_transaction_t* transaction;
 
@@ -858,6 +882,7 @@ void Init_appsignal_extension(void) {
   rb_define_method(Transaction, "set_queue_start", set_transaction_queue_start, 1);
   rb_define_method(Transaction, "set_metadata",    set_transaction_metadata,    2);
   rb_define_method(Transaction, "finish",          finish_transaction,          1);
+  rb_define_method(Transaction, "duplicate",       duplicate_transaction,       1);
   rb_define_method(Transaction, "complete",        complete_transaction,        0);
   rb_define_method(Transaction, "to_json",         transaction_to_json,         0);
 

lib/appsignal/extension/jruby.rb

@@ -132,6 +132,9 @@ def self.lib_extension
         attach_function :appsignal_complete_transaction,
           [:pointer],
           :void
+        attach_function :appsignal_duplicate_transaction,
+          [:pointer, :appsignal_string],
+          :pointer
         attach_function :appsignal_transaction_to_json,
           [:pointer],
           :appsignal_string
@@ -432,6 +435,17 @@ def finish(gc_duration_ms)
           Extension.appsignal_finish_transaction(pointer, gc_duration_ms)
         end
 
+        def duplicate(new_transaction_id)
+          duplicate_transaction = Extension.appsignal_duplicate_transaction(
+            pointer,
+            make_appsignal_string(new_transaction_id)
+          )
+
+          return if !duplicate_transaction || duplicate_transaction.null?
+
+          Transaction.new(duplicate_transaction)
+        end
+
         def complete
           Extension.appsignal_complete_transaction(pointer)
         end

lib/appsignal/transaction.rb

@@ -88,7 +88,7 @@ def clear_current_transaction!
 
     # @api private
     attr_reader :ext, :transaction_id, :action, :namespace, :request, :paused, :tags, :options,
-      :breadcrumbs, :custom_data
+      :breadcrumbs, :custom_data, :is_duplicate
 
     # Use {.create} to create new transactions.
     #
@@ -110,6 +110,7 @@ def initialize(transaction_id, namespace)
       @session_data = nil
       @headers = nil
       @errors = []
+      @is_duplicate = false
 
       @ext = Appsignal::Extension.start_transaction(
         @transaction_id,
@@ -129,24 +130,17 @@ def complete
         return
       end
 
-      sample_data if !@duplicate && @ext.finish(0)
+      sample_data unless @is_duplicate
 
       transactions =
         @errors.each do |error|
-          # This part would be done in the extension like:
-          # transaction = @ext.duplicate_transaction
-
-          transaction = self.class.new(
-            SecureRandom.uuid,
-            namespace,
-            request,
-            options
-          )
-          transaction.ext = ext.duplicate
-          transaction.duplicate = true
-          transaction.set_error(error)
-          transaction.complete
+          transaction.duplicate do |transaction|
+            transaction.set_error(error)
+            transaction.complete
+          end
         end
+
+      @ext.finish(0)
       @ext.complete
 
       transactions.each(&:complete)
@@ -566,6 +560,10 @@ def to_h
     end
     alias_method :to_hash, :to_h
 
+    protected
+
+    attr_writer :ext, :is_duplicate
+
     private
 
     def set_sample_data(key, data)
@@ -608,6 +606,21 @@ def sample_data
       end
     end
 
+    def duplicate
+      self.class.new(
+        SecureRandom.uuid,
+        namespace,
+        request,
+        options
+      ).tap do |transaction|
+        transaction.ext = ext.duplicate(
+          transaction.transaction_id
+        )
+
+        transaction.is_duplicate = true
+      end
+    end
+
     # @api private
     def params
       return unless @params

spec/lib/appsignal/extension_spec.rb

@@ -100,6 +100,10 @@
           subject.finish(0)
         end
 
+        it "should have a duplicate method" do
+          subject.duplicate("request_id")
+        end
+
         it "should have a complete method" do
           subject.complete
         end