add tracer metrics for the agent exporter

LICENSE-3rdparty.csv

@@ -3,6 +3,7 @@ require,@types/node,MIT,Copyright Authors
 require,bowser,MIT,Copyright 2015 Dustin Diaz
 require,container-info,MIT,Copyright 2018 Stephen Belanger
 require,core-js,MIT,Copyright 2014-2019 Denis Pushkarev
+require,hdr-histogram-js,BSD-2-Clause,Copyright 2016 Alexandre Victoor
 require,int64-buffer,MIT,Copyright 2015-2016 Yusuke Kawasaki
 require,koalas,MIT,Copyright 2013-2017 Brian Woodward
 require,limiter,MIT,Copyright 2011 John Hurliman

benchmark/core.js

@@ -19,6 +19,8 @@ const format = require('../packages/dd-trace/src/format')
 const encode = require('../packages/dd-trace/src/encode')
 const config = new Config('benchmark', { service: 'benchmark' })
 const id = require('../packages/dd-trace/src/id')
+const Histogram = require('../packages/dd-trace/src/histogram')
+const histogram = new Histogram()
 
 const suite = benchmark('core')
 
@@ -99,5 +101,10 @@ suite
       id()
     }
   })
+  .add('Histogram', {
+    fn () {
+      histogram.record(Math.round(Math.random() * 3e12))
+    }
+  })
 
 suite.run()

package.json

@@ -52,6 +52,7 @@
     "bowser": "^2.5.3",
     "container-info": "^1.0.1",
     "core-js": "^3.3.4",
+    "hdr-histogram-js": "^1.1.4",
     "int64-buffer": "^0.1.9",
     "koalas": "^1.0.2",
     "limiter": "^1.1.4",

packages/dd-trace/src/exporters/agent/writer.js

@@ -26,6 +26,8 @@ class Writer {
 
     log.debug(() => `Adding encoded trace to buffer: ${buffer.toString('hex').match(/../g).join(' ')}`)
 
+    platform.metrics().histogram('datadog.tracer.node.exporter.agent.trace_size', buffer.length)
+
     if (buffer.length + this._size > MAX_SIZE) {
       this.flush()
     }
@@ -37,9 +39,12 @@ class Writer {
   flush () {
     if (this._queue.length > 0) {
       const data = platform.msgpack.prefix(this._queue)
+      const size = data.reduce((prev, next) => prev + next.length, 0)
 
       this._request(data, this._queue.length)
 
+      platform.metrics().histogram('datadog.tracer.node.exporter.agent.payload_size', size)
+
       this._queue = []
       this._size = 0
     }
@@ -70,7 +75,20 @@ class Writer {
 
     log.debug(() => `Request to the agent: ${JSON.stringify(options)}`)
 
-    platform.request(Object.assign({ data }, options), (err, res) => {
+    platform.metrics().increment('datadog.tracer.node.exporter.agent.requests')
+
+    platform.request(Object.assign({ data }, options), (err, res, status) => {
+      if (status) {
+        platform.metrics().increment('datadog.tracer.node.exporter.agent.responses')
+        platform.metrics().increment('datadog.tracer.node.exporter.agent.responses.by.status', `status:${status}`)
+      } else {
+        platform.metrics().increment('datadog.tracer.node.exporter.agent.errors')
+
+        if (err && err.code) {
+          platform.metrics().increment('datadog.tracer.node.exporter.agent.errors.by.code', `code:${err.code}`)
+        }
+      }
+
       if (err) return log.error(err)
 
       log.debug(`Response from the agent: ${res}`)

packages/dd-trace/src/histogram.js

@@ -0,0 +1,52 @@
+'use strict'
+
+const hdr = require('hdr-histogram-js')
+
+const highestTrackableValue = 3.6e12 // 1 hour
+
+class Histogram {
+  constructor () {
+    this._histogram = hdr.build({
+      highestTrackableValue
+    })
+
+    this.reset()
+  }
+
+  get min () { return this._min }
+  get max () { return this._max }
+  get avg () { return this._count === 0 ? 0 : this._sum / this._count }
+  get sum () { return this._sum }
+  get count () { return this._count }
+  get median () { return this.percentile(50) }
+  get p95 () { return this.percentile(95) }
+
+  percentile (percentile) {
+    return this._histogram.getValueAtPercentile(percentile)
+  }
+
+  record (value) {
+    if (this._count === 0) {
+      this._min = this._max = value
+    } else {
+      this._min = Math.min(this._min, value)
+      this._max = Math.max(this._max, value)
+    }
+
+    this._count++
+    this._sum += value
+
+    this._histogram.recordValue(value)
+  }
+
+  reset () {
+    this._min = 0
+    this._max = 0
+    this._sum = 0
+    this._count = 0
+
+    this._histogram.reset()
+  }
+}
+
+module.exports = Histogram

packages/dd-trace/src/platform/browser/metrics.js

@@ -16,6 +16,8 @@ module.exports = function () {
       }
     },
 
+    histogram () {},
+
     count () {},
 
     increment () {},