fix(otel): Use `req.routePath` when tagging spans (#1113)

* use routePath

Replace indexing into the matchedRoutes with a direct reference to routePath

* Update package.json

Bump version

* set span name and attributes after the request is handled

* revert version bump

* changeset

* add test to ensure subapps set the correct span name

---------

Co-authored-by: Milo Hansen <milo.hansen@avanade.com>

.changeset/ripe-parents-sing.md

@@ -0,0 +1,5 @@
+---
+'@hono/otel': patch
+---
+
+Use `req.routePath` to augment spans with the path that handled the request.

packages/otel/src/index.test.ts

@@ -26,6 +26,13 @@ describe('OpenTelemetry middleware', () => {
     throw new Error('error message')
   })
 
+  const subapp = new Hono()
+  subapp.get('/hello', (c) => c.text('Hello from subapp!'))
+  subapp.get('*', (c) => c.text('Fallthrough'))
+
+  // mount subapp
+  app.route('/subapp', subapp)
+
   it('Should make a span', async () => {
     memoryExporter.reset()
     const response = await app.request('http://localhost/foo')
@@ -71,4 +78,13 @@ describe('OpenTelemetry middleware', () => {
     expect(span.name).toBe('GET /foo')
     expect(span.attributes[ATTR_HTTP_ROUTE]).toBe('/foo')
   })
+
+  // Issue #1112
+  it('Should set the correct span name for subapp', async () => {
+    memoryExporter.reset()
+    await app.request('http://localhost/subapp/hello')
+    const spans = memoryExporter.getFinishedSpans()
+    const [span] = spans
+    expect(span.name).toBe('GET /subapp/hello')
+  })
 })

packages/otel/src/index.ts

@@ -1,5 +1,5 @@
 import type { TracerProvider } from '@opentelemetry/api'
-import { SpanKind, SpanStatusCode,  trace } from '@opentelemetry/api'
+import { SpanKind, SpanStatusCode, trace } from '@opentelemetry/api'
 import {
   ATTR_HTTP_REQUEST_HEADER,
   ATTR_HTTP_REQUEST_METHOD,
@@ -10,17 +10,19 @@ import {
 } from '@opentelemetry/semantic-conventions'
 import type { Env, Input } from 'hono'
 import { createMiddleware } from 'hono/factory'
-import metadata from '../package.json' with { type: 'json'}
+import metadata from '../package.json' with { type: 'json' }
 
 const PACKAGE_NAME = metadata.name
 const PACKAGE_VERSION = metadata.version
 
-export type OtelOptions = {
-  augmentSpan?: false;
-  tracerProvider?: TracerProvider
-} | {
-  augmentSpan: true;
-}
+export type OtelOptions =
+  | {
+      augmentSpan?: false
+      tracerProvider?: TracerProvider
+    }
+  | {
+      augmentSpan: true
+    }
 
 export const otel = <E extends Env = any, P extends string = any, I extends Input = {}>(
   options: OtelOptions = {}
@@ -30,9 +32,9 @@ export const otel = <E extends Env = any, P extends string = any, I extends Inpu
       const result = await next()
       const span = trace.getActiveSpan()
       if (span != null) {
-        const route = c.req.matchedRoutes[c.req.matchedRoutes.length - 1]
-        span.setAttribute(ATTR_HTTP_ROUTE, route.path)
-        span.updateName(`${c.req.method} ${route.path}`)
+        const routePath = c.req.routePath
+        span.setAttribute(ATTR_HTTP_ROUTE, routePath)
+        span.updateName(`${c.req.method} ${routePath}`)
       }
       return result
     })
@@ -40,15 +42,15 @@ export const otel = <E extends Env = any, P extends string = any, I extends Inpu
   const tracerProvider = options.tracerProvider ?? trace.getTracerProvider()
   const tracer = tracerProvider.getTracer(PACKAGE_NAME, PACKAGE_VERSION)
   return createMiddleware<E, P, I>(async (c, next) => {
-    const route = c.req.matchedRoutes[c.req.matchedRoutes.length - 1]
+    const routePath = c.req.routePath
     await tracer.startActiveSpan(
-      `${c.req.method} ${route.path}`,
+      `${c.req.method} ${c.req.routePath}`,
       {
         kind: SpanKind.SERVER,
         attributes: {
           [ATTR_HTTP_REQUEST_METHOD]: c.req.method,
           [ATTR_URL_FULL]: c.req.url,
-          [ATTR_HTTP_ROUTE]: route.path,
+          [ATTR_HTTP_ROUTE]: routePath,
         },
       },
       async (span) => {
@@ -57,6 +59,10 @@ export const otel = <E extends Env = any, P extends string = any, I extends Inpu
         }
         try {
           await next()
+          // Update the span name and route path now that we have the response
+          // because the route path may have changed
+          span.updateName(`${c.req.method} ${c.req.routePath}`)
+          span.setAttribute(ATTR_HTTP_ROUTE, c.req.routePath)
           span.setAttribute(ATTR_HTTP_RESPONSE_STATUS_CODE, c.res.status)
           for (const [name, value] of c.res.headers.entries()) {
             span.setAttribute(ATTR_HTTP_RESPONSE_HEADER(name), value)