Allow customization of trace namespace during the entire trace lifetime

lib/appsignal/span.ex

@@ -135,13 +135,32 @@ defmodule Appsignal.Span do
       |> Appsignal.Span.set_namespace("http_request")
 
   """
-  def set_namespace(%Span{reference: reference} = span, namespace) when is_binary(namespace) do
-    :ok = @nif.set_span_namespace(reference, namespace)
+  def set_namespace(span, namespace) when is_binary(namespace) do
+    set_attribute(span, "appsignal.namespace", namespace)
     span
   end
 
   def set_namespace(span, _name), do: span
 
+  @spec set_namespace_if_nil(t() | nil, String.t()) :: t() | nil
+  @doc """
+  Sets an `Appsignal.Span`'s namespace.  The namespace is `"http_request"` or
+  `"background_job'` to add the span to the "web" and "background" namespaces
+  respectively. Passing another string creates a custom namespace to store the
+  `Appsignal.Span`'s samples in.
+
+  ## Example
+      Appsignal.Tracer.root_span()
+      |> Appsignal.Span.set_namespace("http_request")
+
+  """
+  def set_namespace_if_nil(span, namespace) when is_binary(namespace) do
+    set_attribute(span, "appsignal.namespace_if_nil", namespace)
+    span
+  end
+
+  def set_namespace_if_nil(span, _name), do: span
+
   @spec set_attribute(t() | nil, String.t(), String.t() | integer() | boolean() | float()) ::
           t() | nil
   @doc """

test/appsignal/span_test.exs

@@ -257,8 +257,11 @@ defmodule AppsignalSpanTest do
       assert return == span
     end
 
-    test "sets the namespace through the Nif", %{span: %Span{reference: reference}} do
-      assert [{^reference, "test"}] = Test.Nif.get!(:set_span_namespace)
+    test "sets the namespace as an attribute through the Nif", %{
+      span: %Span{reference: reference}
+    } do
+      assert [{^reference, "appsignal.namespace", "test"}] =
+               Test.Nif.get!(:set_span_attribute_string)
     end
 
     test "returns nil when passing a nil-span" do
@@ -278,7 +281,46 @@ defmodule AppsignalSpanTest do
     end
 
     test "does not set the namespace" do
-      assert :error = Test.Nif.get(:set_span_namespace)
+      assert :error = Test.Nif.get(:set_span_attribute_string)
+    end
+  end
+
+  describe ".set_namespace_if_nil/2" do
+    setup :create_root_span
+
+    setup %{span: span} do
+      %{return: Span.set_namespace_if_nil(span, "test")}
+    end
+
+    test "returns the span", %{return: return, span: span} do
+      assert return == span
+    end
+
+    test "sets the namespace as an attribute through the Nif", %{
+      span: %Span{reference: reference}
+    } do
+      assert [{^reference, "appsignal.namespace_if_nil", "test"}] =
+               Test.Nif.get!(:set_span_attribute_string)
+    end
+
+    test "returns nil when passing a nil-span" do
+      assert Span.set_namespace_if_nil(nil, "test") == nil
+    end
+  end
+
+  describe ".set_namespace_if_nil/2, when passing a non-string namespace" do
+    setup :create_root_span
+
+    setup %{span: span} do
+      %{return: Span.set_namespace_if_nil(span, :non_string)}
+    end
+
+    test "returns the span", %{return: return, span: span} do
+      assert return == span
+    end
+
+    test "does not set the namespace" do
+      assert :error = Test.Nif.get(:set_span_attribute_string)
     end
   end