fix: prevent putDimensions from storing duplicate dimensions

This is a Java-equivalent bug-fix for the Node issue:
awslabs/aws-embedded-metrics-node#20

New conditions check for any matching dimension set before
skipping put dimensions-- to prevent duplicates from being stored.

[TESTING]

Unit test updated to address edge case;
multiple dimension sets added and checked for no duplicates.

Ran integration tests using Docker and compared results in CloudWatch.

Author: Aaron Michael Lamb

src/main/java/software/amazon/cloudwatchlogs/emf/model/MetricDirective.java

@@ -52,6 +52,11 @@ class MetricDirective {
     }
 
     void putDimensionSet(DimensionSet dimensionSet) {
+        if (dimensions.stream()
+                .anyMatch(dim -> dim.getDimensionKeys().equals(dimensionSet.getDimensionKeys()))) {
+            return;
+        }
+
         dimensions.add(dimensionSet);
     }
 

src/test/java/software/amazon/cloudwatchlogs/emf/model/MetricDirectiveTest.java

@@ -114,6 +114,37 @@ public void testPutMultipleDimensionSets() throws JsonProcessingException {
                 "{\"Dimensions\":[[\"Region\"],[\"Instance\"]],\"Metrics\":[],\"Namespace\":\"aws-embedded-metrics\"}");
     }
 
+    @Test
+    public void testPutMultipleDuplicateDimensionSets() throws JsonProcessingException {
+        MetricDirective metricDirective = new MetricDirective();
+        metricDirective.putDimensionSet(DimensionSet.of("Region", "us-east-1"));
+        metricDirective.putDimensionSet(DimensionSet.of("Region", "us-west-2"));
+
+        String serializedMetricDirective = objectMapper.writeValueAsString(metricDirective);
+
+        assertEquals(
+                serializedMetricDirective,
+                "{\"Dimensions\":[[\"Region\"]],\"Metrics\":[],\"Namespace\":\"aws-embedded-metrics\"}");
+    }
+
+    @Test
+    public void testPutMultipleDuplicateDimensionSetsOfDifferentLengths()
+            throws JsonProcessingException {
+        MetricDirective metricDirective = new MetricDirective();
+        metricDirective.putDimensionSet(DimensionSet.of("Region", "us-west-2"));
+        metricDirective.putDimensionSet(
+                DimensionSet.of("Region", "us-east-1", "Instance", "inst-1"));
+        metricDirective.putDimensionSet(DimensionSet.of("Region", "us-west-2"));
+        metricDirective.putDimensionSet(
+                DimensionSet.of("Region", "us-east-1", "Instance", "inst-1"));
+
+        String serializedMetricDirective = objectMapper.writeValueAsString(metricDirective);
+
+        assertEquals(
+                serializedMetricDirective,
+                "{\"Dimensions\":[[\"Region\"],[\"Region\",\"Instance\"]],\"Metrics\":[],\"Namespace\":\"aws-embedded-metrics\"}");
+    }
+
     @Test
     public void testGetDimensionAfterSetDimensions() {
         MetricDirective metricDirective = new MetricDirective();