From 7b82ec1c157b71804d8002397405f983873a44b5 Mon Sep 17 00:00:00 2001
From: George Gooden <george@gecgooden.com>
Date: Wed, 19 Aug 2020 22:08:04 +0800
Subject: [PATCH] feat: reduce root span cardinality in express plugin

Signed-off-by: George Gooden <george@gecgooden.com>
---
 .../node/opentelemetry-plugin-express/src/express.ts   | 10 ++++++++++
 .../opentelemetry-plugin-express/test/express.test.ts  |  2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/plugins/node/opentelemetry-plugin-express/src/express.ts b/plugins/node/opentelemetry-plugin-express/src/express.ts
index 3bcf44d78a..5b46821db5 100644
--- a/plugins/node/opentelemetry-plugin-express/src/express.ts
+++ b/plugins/node/opentelemetry-plugin-express/src/express.ts
@@ -187,6 +187,16 @@ export class ExpressPlugin extends BasePlugin<typeof express> {
         if (plugin._tracer.getCurrentSpan() === undefined) {
           return original.apply(this, arguments);
         }
+        // Rename the root http span once we reach the request handler
+        if (
+          metadata.attributes[AttributeNames.EXPRESS_TYPE] ===
+          ExpressLayerType.REQUEST_HANDLER
+        ) {
+          const parent = plugin._tracer.getCurrentSpan();
+          if (parent) {
+            parent.updateName(`${req.method} ${route}`);
+          }
+        }
         const span = plugin._tracer.startSpan(metadata.name, {
           attributes: Object.assign(attributes, metadata.attributes),
         });
diff --git a/plugins/node/opentelemetry-plugin-express/test/express.test.ts b/plugins/node/opentelemetry-plugin-express/test/express.test.ts
index c9cdf84276..b7ac26a35e 100644
--- a/plugins/node/opentelemetry-plugin-express/test/express.test.ts
+++ b/plugins/node/opentelemetry-plugin-express/test/express.test.ts
@@ -130,7 +130,7 @@ describe('Express Plugin', () => {
         );
         const exportedRootSpan = memoryExporter
           .getFinishedSpans()
-          .find(span => span.name === 'rootSpan');
+          .find(span => span.name === 'GET /toto/:id');
         assert.notStrictEqual(exportedRootSpan, undefined);
       });
       server.close();