fix: Use ConcurrentHashMap for InMemoryProvider

Signed-off-by: Ryan Prayogo <[email protected]>

Author: ryanprayogo

src/main/java/dev/openfeature/sdk/providers/memory/InMemoryProvider.java

@@ -2,10 +2,10 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 import dev.openfeature.sdk.EvaluationContext;
 import dev.openfeature.sdk.EventProvider;
@@ -44,7 +44,7 @@ public Metadata getMetadata() {
     }
 
     public InMemoryProvider(Map<String, Flag<?>> flags) {
-        this.flags = new HashMap<>(flags);
+        this.flags = new ConcurrentHashMap<>(flags);
     }
 
     /**
@@ -67,7 +67,7 @@ public void updateFlags(Map<String, Flag<?>> flags) {
         Set<String> flagsChanged = new HashSet<>();
         flagsChanged.addAll(this.flags.keySet());
         flagsChanged.addAll(flags.keySet());
-        this.flags = new HashMap<>(flags);
+        this.flags = new ConcurrentHashMap<>(flags);
         ProviderEventDetails details = ProviderEventDetails.builder()
             .flagsChanged(new ArrayList<>(flagsChanged))
             .message("flags changed")

src/test/java/dev/openfeature/sdk/providers/memory/InMemoryProviderTest.java

@@ -14,6 +14,8 @@
 
 import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import static dev.openfeature.sdk.Structure.mapToStructure;
 import static dev.openfeature.sdk.testutils.TestFlagsUtils.buildFlags;
@@ -105,4 +107,23 @@ void shouldThrowIfNotInitialized() {
         // ErrorCode.PROVIDER_NOT_READY should be returned when evaluated via the client
         assertThrows(ProviderNotReadyError.class, ()-> inMemoryProvider.getBooleanEvaluation("fail_not_initialized", false, new ImmutableContext()));
     }
+
+    @Test
+    void multithreadedTest() {
+        ExecutorService executorService = Executors.newFixedThreadPool(100);
+        for (int i = 0; i < 10000; i++) {
+            String flagKey = "multithreadedFlag" + i;
+            executorService.submit(() -> {
+                provider.updateFlag(flagKey, Flag.builder()
+                        .variant("on", true)
+                        .variant("off", false)
+                        .defaultVariant("on")
+                        .build());
+            });
+        }
+
+        for (int i = 0; i < 10000; i++) {
+            assertTrue(client.getBooleanValue("multithreadedFlag" + i, false));
+        }
+    }
 }