[serverless] add support for datadog extension (#1265)

* [serverless] add support for datadog extension

* [serverless] pr feedback

Author: DarcyRaynerDD

packages/dd-trace/src/config.js

@@ -114,6 +114,9 @@ class Config {
       rateLimit: coalesce(ingestion.rateLimit, sampler.rateLimit, process.env.DD_TRACE_RATE_LIMIT)
     })
 
+    const inAWSLambda = process.env.AWS_LAMBDA_FUNCTION_NAME !== undefined
+    const defaultFlushInterval = inAWSLambda ? 0 : 2000
+
     this.enabled = isTrue(DD_TRACE_ENABLED)
     this.debug = isTrue(DD_TRACE_DEBUG)
     this.logInjection = isTrue(DD_LOGS_INJECTION)
@@ -122,7 +125,7 @@ class Config {
     this.site = coalesce(options.site, process.env.DD_SITE, 'datadoghq.com')
     this.hostname = DD_AGENT_HOST || (this.url && this.url.hostname)
     this.port = String(DD_TRACE_AGENT_PORT || (this.url && this.url.port))
-    this.flushInterval = coalesce(parseInt(options.flushInterval, 10), 2000)
+    this.flushInterval = coalesce(parseInt(options.flushInterval, 10), defaultFlushInterval)
     this.sampleRate = coalesce(Math.min(Math.max(options.sampleRate, 0), 1), 1)
     this.logger = options.logger
     this.plugins = !!coalesce(options.plugins, true)

packages/dd-trace/src/constants.js

@@ -9,5 +9,6 @@ module.exports = {
   REFERENCE_NOOP: 'noop',
   SAMPLING_RULE_DECISION: '_dd.rule_psr',
   SAMPLING_LIMIT_DECISION: '_dd.limit_psr',
-  SAMPLING_AGENT_DECISION: '_dd.agent_psr'
+  SAMPLING_AGENT_DECISION: '_dd.agent_psr',
+  DATADOG_LAMBDA_EXTENSION_PATH: '/opt/extensions/datadog-agent'
 }

packages/dd-trace/src/exporter.js

@@ -3,16 +3,19 @@
 const AgentExporter = require('./exporters/agent')
 const LogExporter = require('./exporters/log')
 const exporters = require('../../../ext/exporters')
+const fs = require('fs')
+const constants = require('./constants')
 
 module.exports = name => {
   const inAWSLambda = process.env.AWS_LAMBDA_FUNCTION_NAME !== undefined
+  const usingLambdaExtension = inAWSLambda && fs.existsSync(constants.DATADOG_LAMBDA_EXTENSION_PATH)
 
   switch (name) {
     case exporters.LOG:
       return LogExporter
     case exporters.AGENT:
       return AgentExporter
     default:
-      return inAWSLambda ? LogExporter : AgentExporter
+      return inAWSLambda && !usingLambdaExtension ? LogExporter : AgentExporter
   }
 }

packages/dd-trace/test/exporter.spec.js

@@ -1,4 +1,5 @@
 'use strict'
+const fs = require('fs')
 
 const AgentExporter = require('../src/exporters/agent')
 const LogExporter = require('../src/exporters/log')
@@ -29,6 +30,17 @@ describe('exporter', () => {
     expect(Exporter).to.be.equal(LogExporter)
   })
 
+  it('should create an AgentExporter when in Lambda environment with an extension', () => {
+    process.env.AWS_LAMBDA_FUNCTION_NAME = 'my-func'
+    const stub = sinon.stub(fs, 'existsSync')
+    stub.withArgs('/opt/extensions/datadog-agent').returns(true)
+
+    const Exporter = require('../src/exporter')()
+
+    expect(Exporter).to.be.equal(AgentExporter)
+    stub.restore()
+  })
+
   it('should allow configuring the exporter', () => {
     const Exporter = require('../src/exporter')('log')