Improve performance of dogstatsd client and ignore non-string name/tags (#5630)

* performance improvements

* safeguard against non-string keys

* add comment to explain the need for wrapping spies

Author: rochdev

packages/dd-trace/src/dogstatsd.js

@@ -308,12 +308,16 @@ class MetricsAggregationClient {
     }
 
     for (const [tag, next] of node.nodes) {
-      this._captureNode(next, name, tags.concat(tag), fn)
+      tags.push(tag)
+      this._captureNode(next, name, tags, fn)
+      tags.pop()
     }
   }
 
-  _ensureTree (tree, name, tags, value) {
-    tags = tags ? [].concat(tags) : []
+  _ensureTree (tree, name, tags = [], value) {
+    if (!Array.isArray(tags)) {
+      tags = [tags]
+    }
 
     let node = this._ensureNode(tree, name, value)
 
@@ -331,7 +335,10 @@ class MetricsAggregationClient {
 
     if (!node) {
       node = { nodes: new Map(), touched: false, value }
-      container.set(key, node)
+
+      if (typeof key === 'string') {
+        container.set(key, node)
+      }
     }
 
     return node

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

@@ -113,8 +113,22 @@ suiteDescribe('runtimeMetrics', () => {
   let Client
 
   beforeEach(() => {
+    // This is needed because sinon spies keep references to arguments which
+    // breaks tests because the tags parameter is now mutated right after the
+    // call.
+    const wrapSpy = (client, spy) => {
+      return function (stat, value, tags) {
+        return spy.call(client, stat, value, [].concat(tags))
+      }
+    }
+
     Client = sinon.spy(function () {
-      return client
+      return {
+        gauge: wrapSpy(client, client.gauge),
+        increment: wrapSpy(client, client.increment),
+        histogram: wrapSpy(client, client.histogram),
+        flush: client.flush.bind(client)
+      }
     })
 
     Client.generateClientConfig = DogStatsDClient.generateClientConfig