feat: reduce root span cardinality in express plugin

Signed-off-by: George Gooden <george@gecgooden.com>
open-telemetry · Aug 19, 2020 · 7b82ec1 · 7b82ec1
1 parent 58cd219
commit 7b82ec1
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git 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
@@ -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();