feat: set "destination" context for "mongodb" instrumentation (elasti…

…c#1893)

Fixes elastic#1892

CHANGELOG.asciidoc

@@ -14,7 +14,13 @@ endif::[]
 
 [float]
 ===== Features
-* feat: transactionIgnoreUrl wildcard matching {pull}1870[#1870]
+
+* feat: Set "destination" context on spans for "mongodb". {pull}1893[#1893] +
+  This allows Kibana APM Service Maps to show a "mongodb" node for services using
+  the https://www.npmjs.com/package/mongodb[mongodb] package (which includes
+  mongoose and mongojs).
+
+* feat: transactionIgnoreUrl wildcard matching {pull}1870[#1870] +
   Allows users to ignore URLs using simple wildcard matching patterns that behave
   the same across language agents. See https://github.com/elastic/apm/issues/144
 

docs/supported-technologies.asciidoc

@@ -82,7 +82,7 @@ The Node.js agent will automatically instrument the following modules to give yo
 |https://www.npmjs.com/package/memcached[memcached] |>=2.2.0  |Will instrument all commands.
 |https://www.npmjs.com/package/mongodb-core[mongodb-core] |>=1.2.19 <4 |Will instrument all queries.
 A lot of higher level MongoDB modules use mongodb-core,
-so those should be supported as well
+so those should be supported as well.
 |https://www.npmjs.com/package/mongodb[mongodb] |>=2.0.0 <3.3.0 |Supported via mongodb-core
 |https://www.npmjs.com/package/mongodb[mongodb] |^3.3.0 |Will instrument all queries
 |https://www.npmjs.com/package/mongojs[mongojs] |>=1.0.0 <2.7.0 |Supported via mongodb-core

lib/instrumentation/modules/mongodb.js

@@ -1,11 +1,15 @@
 'use strict'
 
 const semver = require('semver')
+const { getDBDestination } = require('../context')
+
+// Match expected `<hostname>:<port>`.
+const HOSTNAME_PORT_RE = /^([^:]+):(\d+)$/
 
 module.exports = (mongodb, agent, { version, enabled }) => {
   if (!enabled) return mongodb
   if (!semver.satisfies(version, '>=3.3')) {
-    agent.logger.debug('mongodb version %s not supported - aborting...', version)
+    agent.logger.debug('mongodb version %s not instrumented (mongodb <3.3 is instrumented via mongodb-core)', version)
     return mongodb
   }
 
@@ -19,6 +23,18 @@ module.exports = (mongodb, agent, { version, enabled }) => {
   return mongodb
 
   function onStart (event) {
+    // `event` is a `CommandStartedEvent`
+    // https://github.com/mongodb/specifications/blob/master/source/command-monitoring/command-monitoring.rst#api
+    // E.g. with [email protected]:
+    //   CommandStartedEvent {
+    //     address: '127.0.0.1:27017',
+    //     connectionId: 1,
+    //     requestId: 1,
+    //     databaseName: 'test',
+    //     commandName: 'insert',
+    //     command:
+    //     { ... } }
+
     const name = [
       event.databaseName,
       collectionFor(event),
@@ -28,6 +44,19 @@ module.exports = (mongodb, agent, { version, enabled }) => {
     const span = agent.startSpan(name, 'db', 'mongodb', 'query')
     if (span) {
       activeSpans.set(event.requestId, span)
+
+      // Per the following code it looks like "<hostname>:<port>" should be
+      // available via the `address` or `connectionId` field.
+      // https://github.com/mongodb/node-mongodb-native/blob/dd356f0ede/lib/core/connection/apm.js#L155-L169
+      const address = event.address || event.connectionId
+      let match
+      if (address && typeof (address) === 'string' &&
+          (match = HOSTNAME_PORT_RE.exec(address))) {
+        span.setDestinationContext(
+          getDBDestination(span, match[1], match[2]))
+      } else {
+        agent.logger.trace('could not set destination context on mongodb span from address=%j', address)
+      }
     }
   }
 

test/instrumentation/modules/mongodb.js

@@ -13,6 +13,9 @@ const test = require('tape')
 
 const mockClient = require('../../_mock_http_client_states')
 
+const host = process.env.MONGODB_HOST || 'localhost'
+const url = `mongodb://${host}:27017`
+
 test('instrument simple command', function (t) {
   resetAgent([
     makeSpanTest(t, 'elasticapm.test.insert'),
@@ -24,9 +27,6 @@ test('instrument simple command', function (t) {
     t.end()
   })
 
-  const host = process.env.MONGODB_HOST || 'localhost'
-  const url = `mongodb://${host}:27017`
-
   const server = new MongoClient(url, {
     useUnifiedTopology: true,
     useNewUrlParser: true
@@ -105,6 +105,21 @@ function makeSpanTest (t, name) {
       t.strictEqual(span.type, 'db', 'span type is "db"')
       t.strictEqual(span.subtype, 'mongodb', 'span subtype is "mongodb"')
       t.strictEqual(span.action, 'query', 'span action is "query"')
+
+      // We can't easily assert destination.address because mongodb >3.5.0
+      // returns a resolved IP for the given connection hostname. In our CI
+      // setup, the host is set to "mongodb" which is a Docker container with
+      // some IP. We could `dns.resolve4()` here, but that's overkill I think.
+      t.ok(span.context.destination.address, 'context.destination.address is defined')
+      t.deepEqual(span.context.destination, {
+        service: {
+          name: 'mongodb',
+          resource: 'mongodb',
+          type: 'db'
+        },
+        address: span.context.destination.address,
+        port: 27017
+      }, 'span.context.destination')
     }
   }
 }