Address misreported value on exemplars for counters.

CHANGELOG.md

@@ -12,6 +12,7 @@ project adheres to [Semantic Versioning](http://semver.org/).
 - Drop support for Node.js versions 16, 18, 20, 21 and 23
 - Metric internal storage ('hashMap') changed to a separate object, LabelMap. If you have
   subclassed the built-in metric types you may need to adjust your code.
+- Counter Exemplars now report the value rather than the delta
 
 ### Changed
 

lib/counter.js

@@ -42,7 +42,7 @@ class Counter extends Metric {
 			throw new Error('It is not possible to decrease a counter');
 		}
 
-		if (value === null || value === undefined) value = 1;
+		value = value ?? 1;
 
 		this.store.validate(labels);
 		this.store.setDelta(labels, value);
@@ -68,7 +68,7 @@ class Counter extends Metric {
 		exemplarLabels = this.defaultExemplarLabelSet,
 	} = {}) {
 		this.incWithoutExemplar(labels, value);
-		this.updateExemplar(labels, exemplarLabels, value);
+		this.updateExemplar(labels, exemplarLabels, this.store.get(labels));
 	}
 
 	updateExemplar(labels, exemplarLabels, value) {

test/exemplarsTest.js

@@ -33,8 +33,11 @@ describe('Exemplars', () => {
 					labelNames: ['method', 'code'],
 					enableExemplars: true,
 				});
+
+				counterInstance.inc({
+					labels: { method: 'get', code: '200' },
+				}); // 1
 				counterInstance.inc({
-					value: 2,
 					labels: { method: 'get', code: '200' },
 					exemplarLabels: { traceId: 'trace_id_test', spanId: 'span_id_test' },
 				});