Work around a concurrent modification issue of KeyValues

benchmarks/benchmarks-core/src/jmh/java/io/micrometer/benchmark/core/ObservationKeyValuesBenchmark.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2024 VMware, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.micrometer.benchmark.core;
+
+import io.micrometer.common.KeyValue;
+import io.micrometer.common.KeyValues;
+import io.micrometer.observation.Observation;
+import org.openjdk.jmh.annotations.*;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.RunnerException;
+import org.openjdk.jmh.runner.options.Options;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+
+import java.util.concurrent.TimeUnit;
+
+@State(Scope.Benchmark)
+@OutputTimeUnit(TimeUnit.MICROSECONDS)
+public class ObservationKeyValuesBenchmark {
+
+    private static final KeyValues KEY_VALUES = KeyValues.of("key1", "value1", "key2", "value2", "key3", "value3",
+            "key4", "value4", "key5", "value5");
+
+    private static final KeyValue KEY_VALUE = KeyValue.of("testKey", "testValue");
+
+    @Benchmark
+    public void noopBaseline() {
+    }
+
+    @Benchmark
+    public Observation.Context contextBaseline() {
+        return new TestContext().addLowCardinalityKeyValues(KEY_VALUES);
+    }
+
+    @Benchmark
+    public Observation.Context putKeyValue() {
+        return new TestContext().addLowCardinalityKeyValues(KEY_VALUES).addLowCardinalityKeyValue(KEY_VALUE);
+    }
+
+    @Benchmark
+    public KeyValues readKeyValues() {
+        return new TestContext().addLowCardinalityKeyValues(KEY_VALUES).getLowCardinalityKeyValues();
+    }
+
+    public static void main(String[] args) throws RunnerException {
+        Options options = new OptionsBuilder().include(ObservationKeyValuesBenchmark.class.getSimpleName())
+            .warmupIterations(5)
+            .measurementIterations(10)
+            .mode(Mode.SampleTime)
+            .forks(1)
+            .build();
+
+        new Runner(options).run();
+    }
+
+    static class TestContext extends Observation.Context {
+
+    }
+
+}

concurrency-tests/src/jcstress/java/io/micrometer/concurrencytests/ObservationContextConcurrencyTest.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2024 VMware, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.micrometer.concurrencytests;
+
+import io.micrometer.common.KeyValue;
+import io.micrometer.observation.Observation;
+import org.openjdk.jcstress.annotations.Actor;
+import org.openjdk.jcstress.annotations.JCStressTest;
+import org.openjdk.jcstress.annotations.Outcome;
+import org.openjdk.jcstress.annotations.State;
+import org.openjdk.jcstress.infra.results.Z_Result;
+
+import java.util.UUID;
+
+import static org.openjdk.jcstress.annotations.Expect.ACCEPTABLE;
+import static org.openjdk.jcstress.annotations.Expect.FORBIDDEN;
+
+public class ObservationContextConcurrencyTest {
+
+    @JCStressTest
+    @State
+    @Outcome(id = "true", expect = ACCEPTABLE)
+    @Outcome(expect = FORBIDDEN)
+    public static class ConsistentKeyValues {
+
+        private final Observation.Context context = new TestContext();
+
+        @Actor
+        public void read(Z_Result r) {
+            try {
+                context.getHighCardinalityKeyValues();
+                r.r1 = true;
+            }
+            catch (Exception e) {
+                r.r1 = false;
+            }
+        }
+
+        @Actor
+        public void write(Z_Result r) {
+            try {
+                String uuid = UUID.randomUUID().toString();
+                context.addHighCardinalityKeyValue(KeyValue.of(uuid, uuid));
+                r.r1 = true;
+            }
+            catch (Exception e) {
+                r.r1 = false;
+            }
+        }
+
+    }
+
+    static class TestContext extends Observation.Context {
+
+    }
+
+}

micrometer-commons/src/main/java/io/micrometer/common/KeyValues.java

@@ -371,7 +371,12 @@ else if (keyValues instanceof KeyValues) {
         }
         else if (keyValues instanceof Collection) {
             Collection<? extends KeyValue> keyValuesCollection = (Collection<? extends KeyValue>) keyValues;
-            return toKeyValues(keyValuesCollection.toArray(EMPTY_KEY_VALUE_ARRAY));
+            try {
+                return toKeyValues(keyValuesCollection.toArray(EMPTY_KEY_VALUE_ARRAY));
+            }
+            catch (ArrayIndexOutOfBoundsException exception) {
+                return of(keyValues);
+            }
         }
         else {
             return toKeyValues(StreamSupport.stream(keyValues.spliterator(), false).toArray(KeyValue[]::new));