fix: emit warn when labels and values are out of sync

.tap/test-results/test/guard.js.tap

@@ -0,0 +1,83 @@
+TAP version 14
+# Subtest: Guard() - object type - should be MetricsGuard
+    ok 1 - should be equal
+    1..1
+ok 1 - Guard() - object type - should be MetricsGuard # time=1.514ms
+
+# Subtest: Guard() - "metricsThreshold" argument is not valid - should throw
+    1..1
+    ok 1 - expected to throw
+ok 2 - Guard() - "metricsThreshold" argument is not valid - should throw # time=2.47ms
+
+# Subtest: Guard() - "permutationThreshold" argument is not valid - should throw
+    1..1
+    ok 1 - expected to throw
+ok 3 - Guard() - "permutationThreshold" argument is not valid - should throw # time=0.346ms
+
+# Subtest: Guard() - "enabled" argument is not valid - should throw
+    1..1
+    ok 1 - expected to throw
+ok 4 - Guard() - "enabled" argument is not valid - should throw # time=0.418ms
+
+# Subtest: Guard() - "permutationThreshold" is at 6 - one metric exceed this - should drop the metric from the stream when exceeding the threshold
+    ok 1 - should be equal
+    ok 2 - should be equal
+    ok 3 - should be equal
+    ok 4 - should be equal
+    ok 5 - should be equal
+    ok 6 - should be equal
+    1..6
+ok 5 - Guard() - "permutationThreshold" is at 6 - one metric exceed this - should drop the metric from the stream when exceeding the threshold # time=3.59ms
+
+# Subtest: Guard() - "metricsThreshold" is at 4 - one metric exceed this - should emit warn event
+    ok 1 - should be equal
+    ok 2 - should be equal
+    1..2
+ok 6 - Guard() - "metricsThreshold" is at 4 - one metric exceed this - should emit warn event # time=0.445ms
+
+# Subtest: Guard() - "enabled" is "false" - metrics exceeds limits - should not interfere and should not store internal metrics
+    ok 1 - should be equal
+    ok 2 - should be equal
+    ok 3 - should be equal
+    1..3
+ok 7 - Guard() - "enabled" is "false" - metrics exceeds limits - should not interfere and should not store internal metrics # time=0.595ms
+
+# Subtest: .getMetrics() - set metrics - call method - should return an Array with metric names without duplicates
+    ok 1 - should be equal
+    ok 2 - should be equal
+    ok 3 - should be equal
+    1..3
+ok 8 - .getMetrics() - set metrics - call method - should return an Array with metric names without duplicates # time=0.496ms
+
+# Subtest: .getLabels() - set metrics - call method - should return an Array with metric names without duplicates
+    ok 1 - should be equal
+    ok 2 - should be equal
+    ok 3 - should be equal
+    ok 4 - should be equal
+    ok 5 - should be equal
+    ok 6 - should be equal
+    1..6
+ok 9 - .getLabels() - set metrics - call method - should return an Array with metric names without duplicates # time=1.978ms
+
+# Subtest: .reset() - set metrics - call method - should empty the guard registry
+    ok 1 - should be equal
+    ok 2 - should be equal
+    ok 3 - should be equal
+    ok 4 - should be equal
+    ok 5 - should be equal
+    1..5
+ok 10 - .reset() - set metrics - call method - should empty the guard registry # time=0.64ms
+
+# Subtest: .pipe() - exceed the default, 10, number of max event listeners - should not cause the process to emit a MaxListenersExceededWarning
+    ok 1 - should be equal
+    1..1
+ok 11 - .pipe() - exceed the default, 10, number of max event listeners - should not cause the process to emit a MaxListenersExceededWarning # time=0.924ms
+
+# Subtest: Guard() - do not add metric where label name / values are null and emit warning
+    ok 1 - should be equal
+    ok 2 - should match pattern
+    ok 3 - should be equal
+    1..3
+ok 12 - Guard() - do not add metric where label name / values are null and emit warning # time=0.402ms
+
+1..12

lib/guard.js

@@ -85,6 +85,9 @@ const MetricsGuard = class MetricsGuard extends stream.Transform {
 		if (labels) {
 			return Array.from(labels.keys()).map((label) => {
 				const [name, value] = label.split(SEPARATOR);
+				if (!name || !value) {
+					this.emit("warn", "metrics", `is null ${name} ${value}`);
+				}
 				return { name, value };
 			});
 		}
@@ -131,18 +134,35 @@ const MetricsGuard = class MetricsGuard extends stream.Transform {
 			this.registry.set(metric.name, entry);
 		}
 
+		let hasInvalidLabelValue = [];
 		// push all label permutations on the metric into the
 		// Set for the metric in the registry. the size of
 		// this Set is compared with the threshold
 		metric.labels.forEach((label) => {
-			entry.add(`${label.name}${SEPARATOR}${label.value}`);
+			if (
+				label &&
+				(label.name === null ||
+					typeof label.name === "undefined" ||
+					label.value === null ||
+					typeof label.value === "undefined")
+			) {
+				hasInvalidLabelValue.push(`${metric.name} label name="${label.name}", value=${label.value}`);
+			} else {
+				entry.add(`${label.name}${SEPARATOR}${label.value}`);
+			}
 		});
 
 		if (metric.source === this.id) {
 			this.emit("drop", metric);
 			next(null);
 			return;
 		}
+		if (hasInvalidLabelValue.length > 0) {
+			// Omit a warning when name or value is null / undefined
+			this.emit("warn", "labels", hasInvalidLabelValue.toString());
+			next(null);
+			return;
+		}
 
 		next(null, metric);
 	}

test/guard.js

@@ -425,3 +425,24 @@ tap.test(
 		});
 	},
 );
+
+tap.test("Guard() - do not add metric where label name / values are null and emit warning", (t) => {
+	const guard = new Guard();
+	const metrics = [new Metric({ name: "foo", description: "foo", labels: [{ name: undefined, value: null }] })];
+
+	const src = srcObjectStream(metrics);
+	const dest = destObjectStream((arr) => {
+		t.equal(arr.length, 0);
+		t.end();
+	});
+
+	guard.on("warn", (type, message) => {
+		t.equal(type, "labels");
+		t.match(message, /undefined/);
+	});
+	src.pipe(guard).pipe(dest);
+
+	setImmediate(() => {
+		dest.end();
+	});
+});