Improve performance of hashObject (#594)

* perf: hashObject: use pre-calculated `sortedLabelNames`

Since label names are predefined ahead-of-time and constant during
runtime, we can sort them before-hand and use them when running `hashObject.

node v18.18.2

```

http fetch GET 200 https://registry.npmjs.org/prom-client 83ms
http fetch GET 200 https://registry.npmjs.org/prom-client/-/prom-client-15.0.0.tgz 42ms
+ prom-client@15.0.0
added 4 packages from 4 contributors and audited 4 packages in 0.382s
found 0 vulnerabilities

- histogram ➭ observe#1 with 64 ➭ current x 104,381 ops/sec ±0.42% (99 runs sampled)
- histogram ➭ observe#1 with 64 ➭ prom-client@latest x 103,709 ops/sec ±0.72% (96 runs sampled)
- histogram ➭ observe#2 with 8 ➭ current x 68,178 ops/sec ±0.20% (98 runs sampled)
- histogram ➭ observe#2 with 8 ➭ prom-client@latest x 53,510 ops/sec ±0.18% (97 runs sampled)
- histogram ➭ observe#2 with 4 and 2 with 2 ➭ current x 34,169 ops/sec ±0.22% (97 runs sampled)
- histogram ➭ observe#2 with 4 and 2 with 2 ➭ prom-client@latest x 28,170 ops/sec ±0.32% (97 runs sampled)
- histogram ➭ observe#2 with 2 and 2 with 4 ➭ current x 36,057 ops/sec ±0.36% (97 runs sampled)
- histogram ➭ observe#2 with 2 and 2 with 4 ➭ prom-client@latest x 28,804 ops/sec ±0.20% (98 runs sampled)
- histogram ➭ observe#6 with 2 ➭ current x 23,360 ops/sec ±0.14% (97 runs sampled)
- histogram ➭ observe#6 with 2 ➭ prom-client@latest x 19,420 ops/sec ±0.36% (96 runs sampled)
- counter ➭ inc ➭ current x 59,643,643 ops/sec ±0.13% (101 runs sampled)
- counter ➭ inc ➭ prom-client@latest x 37,023,723 ops/sec ±0.46% (95 runs sampled)
- counter ➭ inc with labels ➭ current x 84,762 ops/sec ±0.25% (97 runs sampled)
- counter ➭ inc with labels ➭ prom-client@latest x 67,225 ops/sec ±0.62% (95 runs sampled)
- gauge ➭ inc ➭ current x 61,652,788 ops/sec ±0.41% (96 runs sampled)
- gauge ➭ inc ➭ prom-client@latest x 31,247,588 ops/sec ±0.28% (98 runs sampled)
- gauge ➭ inc with labels ➭ current x 86,552 ops/sec ±0.54% (97 runs sampled)
- gauge ➭ inc with labels ➭ prom-client@latest x 64,590 ops/sec ±0.47% (95 runs sampled)
- summary ➭ observe#1 with 64 ➭ current x 87,909 ops/sec ±0.18% (98 runs sampled)
- summary ➭ observe#1 with 64 ➭ prom-client@latest x 94,806 ops/sec ±0.87% (89 runs sampled)
- summary ➭ observe#2 with 8 ➭ current x 61,909 ops/sec ±0.15% (99 runs sampled)
- summary ➭ observe#2 with 8 ➭ prom-client@latest x 49,337 ops/sec ±0.35% (100 runs sampled)
- summary ➭ observe#2 with 4 and 2 with 2 ➭ current x 32,320 ops/sec ±0.20% (100 runs sampled)
- summary ➭ observe#2 with 4 and 2 with 2 ➭ prom-client@latest x 27,597 ops/sec ±0.79% (95 runs sampled)
- summary ➭ observe#2 with 2 and 2 with 4 ➭ current x 32,187 ops/sec ±0.21% (100 runs sampled)
- summary ➭ observe#2 with 2 and 2 with 4 ➭ prom-client@latest x 27,513 ops/sec ±0.37% (93 runs sampled)
- summary ➭ observe#6 with 2 ➭ current x 22,375 ops/sec ±0.47% (94 runs sampled)
- summary ➭ observe#6 with 2 ➭ prom-client@latest x 19,161 ops/sec ±0.14% (100 runs sampled)

┌───────────────────────────────┬────────────────────┬────────────────────┐
│ histogram                     │ current            │ prom-client@latest │
├───────────────────────────────┼────────────────────┼────────────────────┤
│ observe#1 with 64             │ 104381.0327549696  │ 103709.41386205897 │
├───────────────────────────────┼────────────────────┼────────────────────┤
│ observe#2 with 8              │ 68178.1543735591   │ 53509.94862568404  │
├───────────────────────────────┼────────────────────┼────────────────────┤
│ observe#2 with 4 and 2 with 2 │ 34169.376174278514 │ 28170.10920967872  │
├───────────────────────────────┼────────────────────┼────────────────────┤
│ observe#2 with 2 and 2 with 4 │ 36056.509189653516 │ 28804.04102513799  │
├───────────────────────────────┼────────────────────┼────────────────────┤
│ observe#6 with 2              │ 23359.579524196415 │ 19419.640968121184 │
└───────────────────────────────┴────────────────────┴────────────────────┘

┌─────────────────┬───────────────────┬────────────────────┐
│ counter         │ current           │ prom-client@latest │
├─────────────────┼───────────────────┼────────────────────┤
│ inc             │ 59643642.79575977 │ 37023723.28415886  │
├─────────────────┼───────────────────┼────────────────────┤
│ inc with labels │ 84761.87024308582 │ 67224.57758629428  │
└─────────────────┴───────────────────┴────────────────────┘

┌─────────────────┬───────────────────┬────────────────────┐
│ gauge           │ current           │ prom-client@latest │
├─────────────────┼───────────────────┼────────────────────┤
│ inc             │ 61652788.35302279 │ 31247587.722701166 │
├─────────────────┼───────────────────┼────────────────────┤
│ inc with labels │ 86551.57212390135 │ 64589.60038388497  │
└─────────────────┴───────────────────┴────────────────────┘

┌───────────────────────────────┬────────────────────┬────────────────────┐
│ summary                       │ current            │ prom-client@latest │
├───────────────────────────────┼────────────────────┼────────────────────┤
│ observe#1 with 64             │ 87908.71972414361  │ 94806.18075509806  │
├───────────────────────────────┼────────────────────┼────────────────────┤
│ observe#2 with 8              │ 61909.18982275139  │ 49336.623224028765 │
├───────────────────────────────┼────────────────────┼────────────────────┤
│ observe#2 with 4 and 2 with 2 │ 32319.8211562837   │ 27596.72566017053  │
├───────────────────────────────┼────────────────────┼────────────────────┤
│ observe#2 with 2 and 2 with 4 │ 32187.468085238048 │ 27513.002743185254 │
├───────────────────────────────┼────────────────────┼────────────────────┤
│ observe#6 with 2              │ 22375.38970678346  │ 19160.867264237862 │
└───────────────────────────────┴────────────────────┴────────────────────┘

✓ histogram ➭ observe#1 with 64 is 0.6476% faster.
✓ histogram ➭ observe#2 with 8 is 27.41% faster.
✓ histogram ➭ observe#2 with 4 and 2 with 2 is 21.30% faster.
✓ histogram ➭ observe#2 with 2 and 2 with 4 is 25.18% faster.
✓ histogram ➭ observe#6 with 2 is 20.29% faster.
✓ counter ➭ inc is 61.10% faster.
✓ counter ➭ inc with labels is 26.09% faster.
✓ gauge ➭ inc is 97.30% faster.
✓ gauge ➭ inc with labels is 34.00% faster.
⚠ summary ➭ observe#1 with 64 is 7.846% acceptably slower.
✓ summary ➭ observe#2 with 8 is 25.48% faster.
✓ summary ➭ observe#2 with 4 and 2 with 2 is 17.11% faster.
✓ summary ➭ observe#2 with 2 and 2 with 4 is 16.99% faster.
✓ summary ➭ observe#6 with 2 is 16.78% faster.
```

* Add CHANGELOG entry

* hashObject: remove useless `keys` assignment

* fastHashObject: change undefined check

CHANGELOG.md

@@ -12,6 +12,7 @@ project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 
 - remove unnecessary loop from `osMemoryHeapLinux`
+- Improve performance of `hashObject` by using pre-sorted array of label names
 
 ### Added
 

lib/counter.js

@@ -40,7 +40,7 @@ class Counter extends Metric {
 	incWithoutExemplar(labels, value) {
 		let hash = '';
 		if (isObject(labels)) {
-			hash = hashObject(labels);
+			hash = hashObject(labels, this.sortedLabelNames);
 			validateLabel(this.labelNames, labels);
 		} else {
 			value = labels;
@@ -130,7 +130,7 @@ class Counter extends Metric {
 	remove(...args) {
 		const labels = getLabels(this.labelNames, args) || {};
 		validateLabel(this.labelNames, labels);
-		return removeLabels.call(this, this.hashMap, labels);
+		return removeLabels.call(this, this.hashMap, labels, this.sortedLabelNames);
 	}
 }
 

lib/gauge.js

@@ -120,7 +120,7 @@ class Gauge extends Metric {
 	}
 
 	_getValue(labels) {
-		const hash = hashObject(labels || {});
+		const hash = hashObject(labels || {}, this.sortedLabelNames);
 		return this.hashMap[hash] ? this.hashMap[hash].value : 0;
 	}
 
@@ -139,7 +139,7 @@ class Gauge extends Metric {
 	remove(...args) {
 		const labels = getLabels(this.labelNames, args);
 		validateLabel(this.labelNames, labels);
-		removeLabels.call(this, this.hashMap, labels);
+		removeLabels.call(this, this.hashMap, labels, this.sortedLabelNames);
 	}
 }
 
@@ -158,7 +158,7 @@ function setDelta(gauge, labels, delta) {
 	}
 
 	validateLabel(gauge.labelNames, labels);
-	const hash = hashObject(labels);
+	const hash = hashObject(labels, gauge.sortedLabelNames);
 	setValueDelta(gauge.hashMap, delta, labels, hash);
 }
 

lib/histogram.js

@@ -83,7 +83,7 @@ class Histogram extends Metric {
 	}
 
 	updateExemplar(labels, value, exemplarLabels) {
-		const hash = hashObject(labels);
+		const hash = hashObject(labels, this.sortedLabelNames);
 		const bound = findBound(this.upperBounds, value);
 		const { bucketExemplars } = this.hashMap[hash];
 		let exemplar = bucketExemplars[bound];
@@ -132,7 +132,7 @@ class Histogram extends Metric {
 	 * @returns {void}
 	 */
 	zero(labels) {
-		const hash = hashObject(labels);
+		const hash = hashObject(labels, this.sortedLabelNames);
 		this.hashMap[hash] = createBaseValues(
 			labels,
 			this.bucketValues,
@@ -167,7 +167,7 @@ class Histogram extends Metric {
 	remove(...args) {
 		const labels = getLabels(this.labelNames, args);
 		validateLabel(this.labelNames, labels);
-		removeLabels.call(this, this.hashMap, labels);
+		removeLabels.call(this, this.hashMap, labels, this.sortedLabelNames);
 	}
 }
 
@@ -214,7 +214,7 @@ function observe(labels) {
 			);
 		}
 
-		const hash = hashObject(labelValuePair.labels);
+		const hash = hashObject(labelValuePair.labels, this.sortedLabelNames);
 		let valueFromMap = this.hashMap[hash];
 		if (!valueFromMap) {
 			valueFromMap = createBaseValues(

lib/metric.js

@@ -39,10 +39,17 @@ class Metric {
 		if (!validateLabelName(this.labelNames)) {
 			throw new Error('Invalid label name');
 		}
+
 		if (this.collect && typeof this.collect !== 'function') {
 			throw new Error('Optional "collect" parameter must be a function');
 		}
 
+		if (this.labelNames) {
+			this.sortedLabelNames = [...this.labelNames].sort();
+		} else {
+			this.sortedLabelNames = [];
+		}
+
 		this.reset();
 
 		for (const register of this.registers) {

lib/summary.js

@@ -115,7 +115,7 @@ class Summary extends Metric {
 	remove(...args) {
 		const labels = getLabels(this.labelNames, args);
 		validateLabel(this.labelNames, labels);
-		removeLabels.call(this, this.hashMap, labels);
+		removeLabels.call(this, this.hashMap, labels, this.sortedLabelNames);
 	}
 }
 
@@ -170,7 +170,7 @@ function observe(labels) {
 			);
 		}
 
-		const hash = hashObject(labelValuePair.labels);
+		const hash = hashObject(labelValuePair.labels, this.sortedLabelNames);
 		let summaryOfLabel = this.hashMap[hash];
 		if (!summaryOfLabel) {
 			summaryOfLabel = {

lib/util.js

@@ -14,8 +14,12 @@ exports.getValueAsString = function getValueString(value) {
 	}
 };
 
-exports.removeLabels = function removeLabels(hashMap, labels) {
-	const hash = hashObject(labels);
+exports.removeLabels = function removeLabels(
+	hashMap,
+	labels,
+	sortedLabelNames,
+) {
+	const hash = hashObject(labels, sortedLabelNames);
 	delete hashMap[hash];
 };
 
@@ -59,32 +63,44 @@ exports.getLabels = function (labelNames, args) {
 	return acc;
 };
 
-function hashObject(labels) {
-	// We don't actually need a hash here. We just need a string that
-	// is unique for each possible labels object and consistent across
-	// calls with equivalent labels objects.
-	let keys = Object.keys(labels);
+function fastHashObject(keys, labels) {
 	if (keys.length === 0) {
 		return '';
 	}
-	// else
-	if (keys.length > 1) {
-		keys = keys.sort(); // need consistency across calls
-	}
 
 	let hash = '';
-	let i = 0;
-	const size = keys.length;
-	for (; i < size - 1; i++) {
-		hash += `${keys[i]}:${labels[keys[i]]},`;
+
+	for (let i = 0; i < keys.length; i++) {
+		const key = keys[i];
+		const value = labels[key];
+		if (value === undefined) continue;
+
+		hash += `${key}:${value},`;
 	}
-	hash += `${keys[i]}:${labels[keys[i]]}`;
+
 	return hash;
 }
+
+function hashObject(labels, labelNames) {
+	// We don't actually need a hash here. We just need a string that
+	// is unique for each possible labels object and consistent across
+	// calls with equivalent labels objects.
+
+	if (labelNames) {
+		return fastHashObject(labelNames, labels);
+	}
+
+	const keys = Object.keys(labels);
+	if (keys.length > 1) {
+		keys.sort(); // need consistency across calls
+	}
+
+	return fastHashObject(keys, labels);
+}
 exports.hashObject = hashObject;
 
 exports.isObject = function isObject(obj) {
-	return obj === Object(obj);
+	return obj !== null && typeof obj === 'object';
 };
 
 exports.nowTimestamp = function nowTimestamp() {