Fixed concurrency issue with FileBasedStateRepository (#21)

core/src/main/java/org/togglz/core/repository/file/FileBasedStateRepository.java

@@ -53,7 +53,7 @@ public FileBasedStateRepository(File file) {
         log.debug(this.getClass().getSimpleName() + " initialized with: " + file.getAbsolutePath());
     }
 
-    public FeatureState getFeatureState(Feature feature) {
+    public synchronized FeatureState getFeatureState(Feature feature) {
 
         // update file if changed
         fileContent.reloadIfUpdated();
@@ -106,7 +106,7 @@ public FeatureState getFeatureState(Feature feature) {
 
     }
 
-    public void setFeatureState(FeatureState featureState) {
+    public synchronized void setFeatureState(FeatureState featureState) {
 
         // update file if changed
         fileContent.reloadIfUpdated();

core/src/main/java/org/togglz/core/repository/file/FileBasedStateRepositoryConcurrencyTest.java

@@ -0,0 +1,106 @@
+package org.togglz.core.repository.file;
+
+import static org.fest.assertions.api.Assertions.assertThat;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+
+import org.fest.assertions.data.MapEntry;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.togglz.core.Feature;
+import org.togglz.core.repository.FeatureState;
+
+public class FileBasedStateRepositoryConcurrencyTest {
+
+    private File testFile;
+
+    private ExecutorService executor;
+
+    private final int NUMBER_OF_FEATURES = 100;
+
+    @Before
+    public void before() throws IOException {
+        testFile = File.createTempFile(this.getClass().getSimpleName(), "test");
+        executor = Executors.newFixedThreadPool(NUMBER_OF_FEATURES);
+    }
+
+    @Test
+    public void shouldWorkUnderHeavyLoad() throws Exception {
+
+        final FileBasedStateRepository repo = new FileBasedStateRepository(testFile);
+
+        // Step 1: concurrently write a large number of state
+        for (int i = 0; i < NUMBER_OF_FEATURES; i++) {
+
+            // build up a feature state containing some data
+            String name = "FEATURE" + i;
+            Feature feature = new TestFeature(name);
+            final FeatureState state = new FeatureState(feature)
+                .setStrategyId("strategy-for-" + name)
+                .setParameter("param-of-" + name, "some-value-of-" + name);
+
+            // queue a thread writing that state
+            executor.submit(new Runnable() {
+                @Override
+                public void run() {
+                    repo.setFeatureState(state);
+                }
+            });
+
+        }
+
+        // Step 2: Wait for all threads to finish
+        executor.shutdown();
+        executor.awaitTermination(5, TimeUnit.SECONDS);
+
+        // Step 3: Verify the state written to the repository
+        for (int i = 0; i < NUMBER_OF_FEATURES; i++) {
+
+            // read the state
+            String name = "FEATURE" + i;
+            TestFeature feature = new TestFeature(name);
+            FeatureState state = repo.getFeatureState(feature);
+
+            // verify that the state is as expected
+            assertThat(state).isNotNull();
+            assertThat(state.getStrategyId()).isEqualTo("strategy-for-" + name);
+            assertThat(state.getParameterMap())
+                .hasSize(1)
+                .contains(MapEntry.entry("param-of-" + name, "some-value-of-" + name));
+
+        }
+
+    }
+
+    @After
+    public void after() throws Exception {
+        executor.shutdownNow();
+        testFile.delete();
+    }
+
+    private class TestFeature implements Feature {
+
+        private final String name;
+
+        private TestFeature(String name) {
+            this.name = name;
+        }
+
+        @Override
+        public String name() {
+            return name;
+        }
+
+        @Override
+        public boolean isActive() {
+            throw new UnsupportedOperationException();
+        }
+
+    }
+
+}

core/src/main/java/org/togglz/core/repository/file/ReloadablePropertiesFile.java

@@ -16,6 +16,9 @@
 import org.togglz.core.logging.LogFactory;
 import org.togglz.core.util.IOUtils;
 
+/**
+ * Please note that this class is NOT thread-safe.
+ */
 class ReloadablePropertiesFile {
 
     private final Log log = LogFactory.getLog(ReloadablePropertiesFile.class);