Add initial support for Code Origin for Spans

This commit does two things:

1. It lays the groundwork for a new feature called "Code Origin for
   Spans".
2. To showcase this feature, it adds limited support for just Fastify
   entry-spans.

To enable, set `DD_CODE_ORIGIN_FOR_SPANS_ENABLED=true`.

packages/datadog-instrumentations/src/fastify.js

@@ -2,9 +2,13 @@
 
 const shimmer = require('../../datadog-shimmer')
 const { addHook, channel, AsyncResource } = require('./helpers/instrument')
+const { entryTag } = require('../../dd-trace/src/code_origin')
 
 const errorChannel = channel('apm:fastify:middleware:error')
 const handleChannel = channel('apm:fastify:request:handle')
+const codeOriginEnabledChannel = channel('datadog:code-origin-enabled')
+
+const kCodeOriginForSpansTagsSym = Symbol('kCodeOriginForSpansTagsSym')
 
 const parsingResources = new WeakMap()
 
@@ -27,6 +31,11 @@ function wrapFastify (fastify, hasParsingEvents) {
       app.addHook('preHandler', preValidation)
     }
 
+    // Hack to check if the Code Origin for Spans feature is enabled
+    if (codeOriginEnabledChannel.hasSubscribers) {
+      app.addHook('onRoute', onRoute)
+    }
+
     app.addHook = wrapAddHook(app.addHook)
 
     return app
@@ -86,8 +95,9 @@ function onRequest (request, reply, done) {
 
   const req = getReq(request)
   const res = getRes(reply)
+  const tags = getCodeOriginForSpansTags(request)
 
-  handleChannel.publish({ req, res })
+  handleChannel.publish({ req, res, tags })
 
   return done()
 }
@@ -142,6 +152,10 @@ function getRes (reply) {
   return reply && (reply.raw || reply.res || reply)
 }
 
+function getCodeOriginForSpansTags (request) {
+  return request?.routeOptions?.config?.[kCodeOriginForSpansTagsSym]
+}
+
 function publishError (error, req) {
   if (error) {
     errorChannel.publish({ error, req })
@@ -150,6 +164,11 @@ function publishError (error, req) {
   return error
 }
 
+function onRoute (routeOptions) {
+  if (!routeOptions.config) routeOptions.config = {}
+  routeOptions.config[kCodeOriginForSpansTagsSym] = entryTag(onRoute)
+}
+
 addHook({ name: 'fastify', versions: ['>=3'] }, fastify => {
   const wrapped = shimmer.wrapFunction(fastify, fastify => wrapFastify(fastify, true))
 

packages/datadog-instrumentations/src/mocha/common.js

@@ -1,6 +1,6 @@
 const { addHook, channel } = require('../helpers/instrument')
 const shimmer = require('../../../datadog-shimmer')
-const { getCallSites } = require('../../../dd-trace/src/plugins/util/test')
+const { getCallSites } = require('../../../dd-trace/src/plugins/util/stacktrace')
 const { testToStartLine } = require('./utils')
 
 const parameterizedTestCh = channel('ci:mocha:test:parameterize')

packages/datadog-plugin-fastify/src/index.js

@@ -10,9 +10,14 @@ class FastifyPlugin extends RouterPlugin {
   constructor (...args) {
     super(...args)
 
-    this.addSub('apm:fastify:request:handle', ({ req }) => {
+    this.addSub('apm:fastify:request:handle', ({ req, tags }) => {
       this.setFramework(req, 'fastify', this.config)
+      this.setSpanTags(req, tags)
     })
+
+    if (this._tracerConfig.codeOriginForSpansEnabled) {
+      this.addSub('datadog:code-origin-enabled')
+    }
   }
 }
 

packages/datadog-plugin-fastify/test/index.spec.js

@@ -16,6 +16,8 @@ describe('Plugin', () => {
 
   describe('fastify', () => {
     withVersions('fastify', 'fastify', (version, _, specificVersion) => {
+      if (NODE_MAJOR <= 18 && semver.satisfies(specificVersion, '>=5')) return
+
       beforeEach(() => {
         tracer = require('../../dd-trace')
       })
@@ -26,14 +28,12 @@ describe('Plugin', () => {
 
       withExports('fastify', version, ['default', 'fastify'], '>=3', getExport => {
         describe('without configuration', () => {
-          if (NODE_MAJOR <= 18 && semver.satisfies(specificVersion, '>=5')) return
-
           before(() => {
             return agent.load(['fastify', 'find-my-way', 'http'], [{}, {}, { client: false }])
           })
 
           after(() => {
-            return agent.close({ ritmReset: false })
+            return agent.close({ ritmReset: false, wipe: true })
           })
 
           beforeEach(() => {
@@ -542,7 +542,193 @@ describe('Plugin', () => {
             })
           }
         })
+
+        describe('with tracer config codeOriginForSpansEnabled', () => {
+          if (semver.satisfies(specificVersion, '<4')) return // TODO: Why doesn't it work on older versions?
+
+          before(() => {
+            return agent.load(
+              ['fastify', 'find-my-way', 'http'],
+              [{}, {}, { client: false }],
+              { codeOriginForSpansEnabled: true }
+            )
+          })
+
+          after(() => {
+            return agent.close({ ritmReset: false, wipe: true })
+          })
+
+          beforeEach(() => {
+            fastify = getExport()
+            app = fastify()
+
+            if (semver.intersects(version, '>=3')) {
+              return app.register(require('../../../versions/middie').get())
+            }
+          })
+
+          it('should add code_origin tag on entry spans when feature is enabled', done => {
+            let routeRegisterLine
+
+            // Wrap in a named function to have at least one frame with a function name
+            function wrapperFunction () {
+              routeRegisterLine = getNextLineNumber()
+              app.get('/user', function userHandler (request, reply) {
+                reply.send()
+              })
+            }
+
+            const callWrapperLine = getNextLineNumber()
+            wrapperFunction()
+
+            app.listen(() => {
+              const port = app.server.address().port
+
+              agent
+                .use(traces => {
+                  const spans = traces[0]
+                  const tags = spans[0].meta
+
+                  expect(tags).to.have.property('_dd.code_origin.type', 'entry')
+
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.file', __filename)
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.line', routeRegisterLine)
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.method', 'wrapperFunction')
+                  expect(tags).to.not.have.property('_dd.code_origin.frames.0.type')
+
+                  expect(tags).to.have.property('_dd.code_origin.frames.1.file', __filename)
+                  expect(tags).to.have.property('_dd.code_origin.frames.1.line', callWrapperLine)
+                  expect(tags).to.not.have.property('_dd.code_origin.frames.1.method')
+                  expect(tags).to.have.property('_dd.code_origin.frames.1.type', 'Context')
+
+                  expect(tags).to.not.have.property('_dd.code_origin.frames.2.file')
+                })
+                .then(done)
+                .catch(done)
+
+              axios
+                .get(`http://localhost:${port}/user`)
+                .catch(done)
+            })
+          })
+
+          it('should point to where actual route handler is configured, not the prefix', done => {
+            let routeRegisterLine
+
+            app.register(function v1Handler (app, opts, done) {
+              routeRegisterLine = getNextLineNumber()
+              app.get('/user', function userHandler (request, reply) {
+                reply.send()
+              })
+              done()
+            }, { prefix: '/v1' })
+
+            app.listen(() => {
+              const port = app.server.address().port
+
+              agent
+                .use(traces => {
+                  const spans = traces[0]
+                  const tags = spans[0].meta
+
+                  expect(tags).to.have.property('_dd.code_origin.type', 'entry')
+
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.file', __filename)
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.line', routeRegisterLine)
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.method', 'v1Handler')
+                  expect(tags).to.not.have.property('_dd.code_origin.frames.0.type')
+
+                  expect(tags).to.not.have.property('_dd.code_origin.frames.1.file')
+                })
+                .then(done)
+                .catch(done)
+
+              axios
+                .get(`http://localhost:${port}/v1/user`)
+                .catch(done)
+            })
+          })
+
+          it('should point to route handler even if passed through a middleware', function testCase (done) {
+            app.use(function middleware (req, res, next) {
+              next()
+            })
+
+            const routeRegisterLine = getNextLineNumber()
+            app.get('/user', function userHandler (request, reply) {
+              reply.send()
+            })
+
+            app.listen({ host, port: 0 }, () => {
+              const port = app.server.address().port
+
+              agent
+                .use(traces => {
+                  const spans = traces[0]
+                  const tags = spans[0].meta
+
+                  expect(tags).to.have.property('_dd.code_origin.type', 'entry')
+
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.file', __filename)
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.line', routeRegisterLine)
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.method', 'testCase')
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.type', 'Context')
+
+                  expect(tags).to.not.have.property('_dd.code_origin.frames.1.file')
+                })
+                .then(done)
+                .catch(done)
+
+              axios
+                .get(`http://localhost:${port}/user`)
+                .catch(done)
+            })
+          })
+
+          // TODO: In Fastify, the route is resolved before the middleware is called, so we actually can get the line
+          // number of where the route handler is defined. However, this might not be the right choice and it might be
+          // better to point to the middleware.
+          it.skip('should point to middleware if middleware responds early', function testCase (done) {
+            const middlewareRegisterLine = getNextLineNumber()
+            app.use(function middleware (req, res, next) {
+              res.end()
+            })
+
+            app.get('/user', function userHandler (request, reply) {
+              reply.send()
+            })
+
+            app.listen({ host, port: 0 }, () => {
+              const port = app.server.address().port
+
+              agent
+                .use(traces => {
+                  const spans = traces[0]
+                  const tags = spans[0].meta
+
+                  expect(tags).to.have.property('_dd.code_origin.type', 'entry')
+
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.file', __filename)
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.line', middlewareRegisterLine)
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.method', 'testCase')
+                  expect(tags).to.have.property('_dd.code_origin.frames.0.type', 'Context')
+
+                  expect(tags).to.not.have.property('_dd.code_origin.frames.1.file')
+                })
+                .then(done)
+                .catch(done)
+
+              axios
+                .get(`http://localhost:${port}/user`)
+                .catch(done)
+            })
+          })
+        })
       })
     })
   })
 })
+
+function getNextLineNumber () {
+  return String(Number(new Error().stack.split('\n')[2].match(/:(\d+):/)[1]) + 1)
+}

packages/datadog-plugin-web/src/index.js

@@ -15,6 +15,10 @@ class WebPlugin extends Plugin {
   setFramework (req, name, config) {
     web.setFramework(req, name, config)
   }
+
+  setSpanTags (req, tags) {
+    web.setSpanTags(req, tags)
+  }
 }
 
 module.exports = WebPlugin

packages/dd-trace/src/code_origin.js

@@ -0,0 +1,37 @@
+'use strict'
+
+const { getUserLandFrames } = require('./plugins/util/stacktrace')
+
+const limit = Number(process.env._DD_CODE_ORIGIN_MAX_USER_FRAMES) || 8
+
+module.exports = {
+  entryTag,
+  exitTag
+}
+
+function entryTag (topOfStackFunc) {
+  return tag('entry', topOfStackFunc)
+}
+
+function exitTag (topOfStackFunc) {
+  return tag('exit', topOfStackFunc)
+}
+
+function tag (type, topOfStackFunc) {
+  const frames = getUserLandFrames(topOfStackFunc, limit)
+  const tags = {
+    '_dd.code_origin.type': type
+  }
+  for (let i = 0; i < frames.length; i++) {
+    const frame = frames[i]
+    tags[`_dd.code_origin.frames.${i}.file`] = frame.file
+    tags[`_dd.code_origin.frames.${i}.line`] = String(frame.line)
+    if (frame.method) {
+      tags[`_dd.code_origin.frames.${i}.method`] = frame.method
+    }
+    if (frame.type) {
+      tags[`_dd.code_origin.frames.${i}.type`] = frame.type
+    }
+  }
+  return tags
+}

packages/dd-trace/src/config.js

@@ -464,6 +464,7 @@ class Config {
     this._setValue(defaults, 'appsec.wafTimeout', 5e3) // µs
     this._setValue(defaults, 'clientIpEnabled', false)
     this._setValue(defaults, 'clientIpHeader', null)
+    this._setValue(defaults, 'codeOriginForSpansEnabled', false)
     this._setValue(defaults, 'dbmPropagationMode', 'disabled')
     this._setValue(defaults, 'dogstatsd.hostname', '127.0.0.1')
     this._setValue(defaults, 'dogstatsd.port', '8125')
@@ -572,6 +573,7 @@ class Config {
       DD_APPSEC_RASP_ENABLED,
       DD_APPSEC_TRACE_RATE_LIMIT,
       DD_APPSEC_WAF_TIMEOUT,
+      DD_CODE_ORIGIN_FOR_SPANS_ENABLED,
       DD_DATA_STREAMS_ENABLED,
       DD_DBM_PROPAGATION_MODE,
       DD_DOGSTATSD_HOSTNAME,
@@ -702,6 +704,7 @@ class Config {
     this._envUnprocessed['appsec.wafTimeout'] = DD_APPSEC_WAF_TIMEOUT
     this._setBoolean(env, 'clientIpEnabled', DD_TRACE_CLIENT_IP_ENABLED)
     this._setString(env, 'clientIpHeader', DD_TRACE_CLIENT_IP_HEADER)
+    this._setBoolean(env, 'codeOriginForSpansEnabled', DD_CODE_ORIGIN_FOR_SPANS_ENABLED)
     this._setString(env, 'dbmPropagationMode', DD_DBM_PROPAGATION_MODE)
     this._setString(env, 'dogstatsd.hostname', DD_DOGSTATSD_HOSTNAME)
     this._setString(env, 'dogstatsd.port', DD_DOGSTATSD_PORT)
@@ -868,6 +871,7 @@ class Config {
     this._optsUnprocessed['appsec.wafTimeout'] = options.appsec.wafTimeout
     this._setBoolean(opts, 'clientIpEnabled', options.clientIpEnabled)
     this._setString(opts, 'clientIpHeader', options.clientIpHeader)
+    this._setBoolean(opts, 'codeOriginForSpansEnabled', options.codeOriginForSpansEnabled)
     this._setString(opts, 'dbmPropagationMode', options.dbmPropagationMode)
     if (options.dogstatsd) {
       this._setString(opts, 'dogstatsd.hostname', options.dogstatsd.hostname)