Perf improvements when adding metrics

CHANGES.md

@@ -4,6 +4,7 @@ CHANGELOG
 ## Unreleased
 
 * @bdeitte Fill in some missing areas for automated tests
+* @bdeitte CPU performance improvements: pre-join global tags, eliminate Buffer round-trip for TCP/stream, cache byteLength, use hrtime.bigint, optimize overrideTags
 
 ## 14.0.0 (2026-2-15)
 

lib/helpers.js

@@ -96,38 +96,75 @@ function overrideTags (parent, child, telegraf) {
     return parent;
   }
 
-  const childCopy = {};
+  const formattedChild = formatTags(child, telegraf);
+
+  // Fast path: if no child tag key appears in the parent, just concatenate.
+  // This is the common case when per-metric tags don't overlap with global tags.
+  const parentKeys = new Set();
+  for (const tag of parent) {
+    const idx = typeof tag === 'string' ? tag.indexOf(':') : -1;
+    if (idx > 0) {
+      parentKeys.add(tag.substring(0, idx));
+    }
+  }
+
+  let hasOverlap = false;
+  const kvTags = [];
+  const valueTags = [];
+  for (const tag of formattedChild) {
+    const idx = typeof tag === 'string' ? tag.indexOf(':') : -1;
+    if (idx < 1) {
+      valueTags.push(tag);
+    } else {
+      kvTags.push(tag);
+      if (parentKeys.has(tag.substring(0, idx))) {
+        hasOverlap = true;
+        break;
+      }
+    }
+  }
+
+  if (!hasOverlap) {
+    // Fast path: key:value child tags first, then value-only child tags (matching slow-path ordering)
+    const result = parent.concat(kvTags);
+    result.push(...valueTags);
+    return result;
+  }
+
+  // Slow path: rebuild parent, replacing tags whose keys appear in child.
+  const childCopy = new Map();
   const toAppend = [];
 
-  formatTags(child, telegraf).forEach(tag => {
+  formattedChild.forEach(tag => {
     const idx = typeof tag === 'string' ? tag.indexOf(':') : -1;
-    if (idx < 1) { // Not found or first character
+    if (idx < 1) {
       toAppend.push(tag);
     } else {
       const key = tag.substring(0, idx);
       const value = tag.substring(idx + 1);
-      childCopy[key] = childCopy[key] || [];
-      childCopy[key].push(value);
+      if (!childCopy.has(key)) {
+        childCopy.set(key, []);
+      }
+      childCopy.get(key).push(value);
     }
   });
 
   const result = parent.filter(tag => {
     const idx = typeof tag === 'string' ? tag.indexOf(':') : -1;
-    if (idx < 1) { // Not found or first character
+    if (idx < 1) {
       return true;
     }
-
     const key = tag.substring(0, idx);
-
-    return !childCopy.hasOwnProperty(key);
+    return !childCopy.has(key);
   });
 
-  Object.keys(childCopy).forEach(key => {
-    for (const value of childCopy[key]) {
+  for (const [key, values] of childCopy) {
+    for (const value of values) {
       result.push(`${key}:${value}`);
     }
-  });
-  return result.concat(toAppend);
+  }
+  result.push(...toAppend);
+  return result;
 }
 
 /**

lib/statsFunctions.js

@@ -36,15 +36,11 @@ function applyStatsFns (Client) {
 
     return (...args) => {
       const ctx = createTimerContext();
-      const start = process.hrtime();
+      const start = process.hrtime.bigint();
       try {
         return func(...args, ctx);
       } finally {
-        // get duration in milliseconds
-        const durationComponents = process.hrtime(start);
-        const seconds = durationComponents[0];
-        const nanoseconds = durationComponents[1];
-        const duration = (seconds * 1000) + (nanoseconds / 1E6);
+        const duration = Number(process.hrtime.bigint() - start) / 1e6;
 
         const finalTags = mergeTags(tags, ctx.getTags(), _this.telegraf);
         _this.timing(
@@ -118,14 +114,10 @@ function applyStatsFns (Client) {
    * High-resolution timer
    */
   function hrtimer() {
-    const start = process.hrtime();
+    const start = process.hrtime.bigint();
 
     return () => {
-      const durationComponents = process.hrtime(start);
-      const seconds = durationComponents[0];
-      const nanoseconds = durationComponents[1];
-      const duration = (seconds * 1000) + (nanoseconds / 1E6);
-      return duration;
+      return Number(process.hrtime.bigint() - start) / 1e6;
     };
   }
 

lib/statsd.js

@@ -82,6 +82,8 @@ const Client = function (host, port, prefix, suffix, globalize, cacheDns, mock,
         concat(availableDDEnvs.map(env => `${DD_ENV_GLOBAL_TAGS_MAPPING[env]}:${helpers.sanitizeTags(process.env[env])}`));
     }
   }
+  this._globalTagStr = this.globalTags.length > 0 ?
+      `|${this.tagPrefix}${this.globalTags.join(this.tagSeparator)}` : '';
   this.telegraf = options.telegraf || false;
   if (options.maxBufferSize !== undefined) {
     this.maxBufferSize = options.maxBufferSize;
@@ -359,7 +361,11 @@ Client.prototype.send = function (message, tags, callback) {
         return tag.substring(0, idx) + '=' + tag.substring(idx + 1);
       }).join(',');
       message = `${message[0]},${tagStr}:${message.slice(1).join(':')}`;
+    } else if (mergedTags === this.globalTags) {
+      // Fast path: no per-metric tags, use pre-joined string
+      message += this._globalTagStr;
     } else {
+      // Slow path: per-metric tags were merged, must rejoin
       message += `|${this.tagPrefix}${mergedTags.join(this.tagSeparator)}`;
     }
   }
@@ -505,7 +511,7 @@ Client.prototype.sendMessage = function (message, callback, isTelemetry) {
         protocolErrorHandler(this, this.protocol, err);
       }
     } else {
-      debug('hot-shots sendMessage: successfully sent %d bytes', Buffer.byteLength(message));
+      debug('hot-shots sendMessage: successfully sent %d bytes', messageBytes);
       // Track bytes sent successfully (only for non-telemetry messages)
       if (this.telemetry && !isTelemetry) {
         this.telemetry.recordBytesSent(messageBytes);
@@ -528,7 +534,10 @@ Client.prototype.sendMessage = function (message, callback, isTelemetry) {
     this.messagesInFlight++;
     debug('hot-shots sendMessage: sending %d bytes via %s transport (messagesInFlight=%d)',
       Buffer.byteLength(message), this.protocol, this.messagesInFlight);
-    this.socket.send(Buffer.from(message), handleCallback);
+    const payload = (this.protocol === PROTOCOL.TCP || this.protocol === PROTOCOL.STREAM) ?
+      message :
+      Buffer.from(message);
+    this.socket.send(payload, handleCallback);
   } catch (err) {
     debug('hot-shots sendMessage: exception during send - %s', err.message);
     handleCallback(err);
@@ -671,6 +680,8 @@ const ChildClient = function (parent, options) {
     // Child inherits telemetry from parent (for metric tracking)
     telemetry   : parent.telemetry
   });
+  this._globalTagStr = this.globalTags.length > 0 ?
+      `|${this.tagPrefix}${this.globalTags.join(this.tagSeparator)}` : '';
 };
 util.inherits(ChildClient, Client);
 

lib/transport.js

@@ -14,14 +14,14 @@ let unixDgram;
 const UDS_PATH_DEFAULT = '/var/run/datadog/dsd.socket';
 
 /**
- * Ensures a buffer ends with a newline character for line-based protocols.
- * @param {Buffer} buf - The buffer to check and modify
- * @returns {string} The buffer content as a string with newline appended if needed
+ * Ensures a message ends with a newline character for line-based protocols.
+ * @param {Buffer|string} buf - The buffer or string to check and modify
+ * @returns {string} The message as a string with newline appended if needed
  */
 const addEol = (buf) => {
-  let msg = buf.toString();
+  const msg = typeof buf === 'string' ? buf : buf.toString();
   if (msg.length > 0 && msg[msg.length - 1] !== '\n') {
-    msg += '\n';
+    return msg + '\n';
   }
   return msg;
 };