Adds an option to allow removal of low & high cardinality key values (#3529)

(cherry picked from commit 8a7c662)

Author: marcingrzejszczak

micrometer-observation/src/main/java/io/micrometer/observation/Observation.java

@@ -20,6 +20,7 @@
 import io.micrometer.common.lang.NonNull;
 import io.micrometer.common.lang.Nullable;
 
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.Map;
@@ -941,6 +942,30 @@ public Context addHighCardinalityKeyValue(KeyValue keyValue) {
             return this;
         }
 
+        /**
+         * Removes a low cardinality key value by looking at its key - those will be
+         * removed to those fetched from the
+         * {@link ObservationConvention#getLowCardinalityKeyValues(Context)} method.
+         * @param keyName name of the key
+         * @return this context
+         */
+        public Context removeLowCardinalityKeyValue(String keyName) {
+            this.lowCardinalityKeyValues.remove(keyName);
+            return this;
+        }
+
+        /**
+         * Removes a high cardinality key value by looking at its key - those will be
+         * removed to those fetched from the
+         * {@link ObservationConvention#getHighCardinalityKeyValues(Context)} method.
+         * @param keyName name of the key
+         * @return this context
+         */
+        public Context removeHighCardinalityKeyValue(String keyName) {
+            this.highCardinalityKeyValues.remove(keyName);
+            return this;
+        }
+
         /**
          * Adds multiple low cardinality key values at once.
          * @param keyValues collection of key values
@@ -961,6 +986,26 @@ public Context addHighCardinalityKeyValues(KeyValues keyValues) {
             return this;
         }
 
+        /**
+         * Removes multiple low cardinality key values at once.
+         * @param keyNames collection of key names
+         * @return this context
+         */
+        public Context removeLowCardinalityKeyValues(String... keyNames) {
+            Arrays.stream(keyNames).forEach(this::removeLowCardinalityKeyValue);
+            return this;
+        }
+
+        /**
+         * Removes multiple high cardinality key values at once.
+         * @param keyNames collection of key names
+         * @return this context
+         */
+        public Context removeHighCardinalityKeyValues(String... keyNames) {
+            Arrays.stream(keyNames).forEach(this::removeHighCardinalityKeyValue);
+            return this;
+        }
+
         @NonNull
         @Override
         public KeyValues getLowCardinalityKeyValues() {

micrometer-observation/src/test/java/io/micrometer/observation/ObservationContextTest.java

@@ -16,6 +16,7 @@
 package io.micrometer.observation;
 
 import io.micrometer.common.KeyValue;
+import io.micrometer.common.KeyValues;
 import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -131,4 +132,26 @@ void sameKeyShouldOverrideKeyValue() {
         assertThat(context.getHighCardinalityKeyValues()).containsExactly(newHigh);
     }
 
+    @Test
+    void removingLowCardinalityKeysShouldBePossible() {
+        context.addLowCardinalityKeyValues(KeyValues.of(KeyValue.of("key", "VALUE"), KeyValue.of("key2", "VALUE2"),
+                KeyValue.of("key3", "VALUE3"), KeyValue.of("key4", "VALUE4")));
+
+        context.removeLowCardinalityKeyValue("key");
+        context.removeLowCardinalityKeyValues("key3", "key4");
+
+        assertThat(context.getLowCardinalityKeyValues()).containsExactly(KeyValue.of("key2", "VALUE2"));
+    }
+
+    @Test
+    void removingHighCardinalityKeysShouldBePossible() {
+        context.addHighCardinalityKeyValues(KeyValues.of(KeyValue.of("key", "VALUE"), KeyValue.of("key2", "VALUE2"),
+                KeyValue.of("key3", "VALUE3"), KeyValue.of("key4", "VALUE4")));
+
+        context.removeHighCardinalityKeyValue("key");
+        context.removeHighCardinalityKeyValues("key3", "key4");
+
+        assertThat(context.getHighCardinalityKeyValues()).containsExactly(KeyValue.of("key2", "VALUE2"));
+    }
+
 }