Allow customizing the span name

lib/opencensus_tesla.ex

@@ -16,14 +16,24 @@ defmodule OpencensusTesla.Middleware do
     plug OpencensusTesla.Middleware
   end
   ```
+
+  ### Options
+
+  Following Middleware options are accepted:
+    - `span_name_override` - if provided, will be used as the
+      span name. Otherwise request path is used by default.
+      A function taking the request path as argument and
+      returning a string to use as span name is expected.
   """
 
   import Opencensus.Trace
 
-  def call(env, next, _options) do
+  def call(env, next, options) do
     uri = %URI{path: path} = URI.parse(env.url)
+    span_name_function = Keyword.get(options, :span_name_override)
+    span_name = if span_name_function, do: span_name_function.(path), else: path
 
-    with_child_span(path, http_attributes(env, uri)) do
+    with_child_span(span_name, http_attributes(env, uri)) do
       span_ctx = :ocp.current_span_ctx()
       headers = :oc_propagation_http_tracecontext.to_headers(span_ctx)
 

test/opencensus_tesla_test.exs

@@ -14,20 +14,48 @@ defmodule TestRequestClient do
   end)
 end
 
+defmodule TestRequestClientCustomized do
+  use Tesla
+
+  plug(OpencensusTesla.Middleware, span_name_override: fn path -> path <> "test" end)
+
+  adapter(fn env ->
+    {status, headers, body} =
+      case env.url do
+        _ ->
+          {200, [], ""}
+      end
+
+    {:ok, %{env | status: status, headers: headers, body: body}}
+  end)
+end
+
 defmodule OpencensusTeslaTest do
   use ExUnit.Case
 
-  test "span is reported after request is complete" do
+  setup do
     Application.load(:opencensus)
     Application.put_env(:opencensus, :send_interval_ms, 1)
     Application.put_env(:opencensus, :reporters, [{:oc_reporter_pid, self()}])
 
     {:ok, _} = Application.ensure_all_started(:opencensus)
     {:ok, _} = Application.ensure_all_started(:opencensus_elixir)
 
+    on_exit(fn -> Application.stop(:opencensus) end)
+    :ok
+  end
+
+  test "span is reported after request is complete" do
     {:ok, env} = TestRequestClient.post("/", "")
     assert 200 = env.status
 
-    assert_receive {:span, _}, 1_000
+    assert_receive {:span, {:span, "/", _, _, _, _, _, _, _, _, _, _, _, _, _, _, _}}, 1_000
+  end
+
+  test "can override span name" do
+    {:ok, env} = TestRequestClientCustomized.post("/", "")
+    assert 200 = env.status
+
+    assert_receive {:span, {:span, "/test", _, _, _, _, _, _, _, _, _, _, _, _, _, _, _}}, 1_000
   end
 end