feat: Added caching for OptimizelyConfig object (#352)

## Summary
Updated the `OptimizelyConfig` implementation to always return cached object. `OptimizelyConfig` object will only be updated only when new `ProjectConfig` is received.

## Test Plan
Added Unit tests

Author: fayyazarshad

core-api/src/main/java/com/optimizely/ab/Optimizely.java

@@ -29,6 +29,7 @@
 import com.optimizely.ab.event.internal.payload.EventBatch;
 import com.optimizely.ab.notification.*;
 import com.optimizely.ab.optimizelyconfig.OptimizelyConfig;
+import com.optimizely.ab.optimizelyconfig.OptimizelyConfigManager;
 import com.optimizely.ab.optimizelyconfig.OptimizelyConfigService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -87,6 +88,9 @@ public class Optimizely implements AutoCloseable {
 
     private final ProjectConfigManager projectConfigManager;
 
+    @Nullable
+    private final OptimizelyConfigManager optimizelyConfigManager;
+
     // TODO should be private
     public final NotificationCenter notificationCenter;
 
@@ -99,6 +103,7 @@ private Optimizely(@Nonnull EventHandler eventHandler,
                        @Nonnull DecisionService decisionService,
                        @Nullable UserProfileService userProfileService,
                        @Nonnull ProjectConfigManager projectConfigManager,
+                       @Nullable OptimizelyConfigManager optimizelyConfigManager,
                        @Nonnull NotificationCenter notificationCenter
     ) {
         this.eventHandler = eventHandler;
@@ -107,6 +112,7 @@ private Optimizely(@Nonnull EventHandler eventHandler,
         this.decisionService = decisionService;
         this.userProfileService = userProfileService;
         this.projectConfigManager = projectConfigManager;
+        this.optimizelyConfigManager = optimizelyConfigManager;
         this.notificationCenter = notificationCenter;
     }
 
@@ -884,20 +890,6 @@ public Variation getForcedVariation(@Nonnull String experimentKey,
         return decisionService.getForcedVariation(experiment, userId);
     }
 
-    /**
-     * Get {@link OptimizelyConfig} containing experiments and features map
-     *
-     * @return {@link OptimizelyConfig}
-     */
-    public OptimizelyConfig getOptimizelyConfig() {
-        ProjectConfig projectConfig = getProjectConfig();
-        if (projectConfig == null) {
-            logger.error("Optimizely instance is not valid, failing getOptimizelyConfig call.");
-            return null;
-        }
-        return new OptimizelyConfigService(projectConfig).getConfig();
-    }
-
     /**
      * @return the current {@link ProjectConfig} instance.
      */
@@ -928,6 +920,25 @@ private boolean validateUserId(String userId) {
         return true;
     }
 
+    /**
+     * Get {@link OptimizelyConfig} containing experiments and features map
+     *
+     * @return {@link OptimizelyConfig}
+     */
+    public OptimizelyConfig getOptimizelyConfig() {
+        ProjectConfig projectConfig = getProjectConfig();
+        if (projectConfig == null) {
+            logger.error("Optimizely instance is not valid, failing getOptimizelyConfig call.");
+            return null;
+        }
+        if (optimizelyConfigManager != null) {
+            return optimizelyConfigManager.getOptimizelyConfig();
+        }
+        // Generate and return a new OptimizelyConfig object as a fallback when consumer implements their own ProjectConfigManager without implementing OptimizelyConfigManager.
+        logger.debug("optimizelyConfigManager is null, generating new OptimizelyConfigObject as a fallback");
+        return new OptimizelyConfigService(projectConfig).getConfig();
+    }
+
     /**
      * Helper method which makes separate copy of attributesMap variable and returns it
      *
@@ -1029,6 +1040,7 @@ public static class Builder {
         private EventProcessor eventProcessor;
         private ProjectConfig projectConfig;
         private ProjectConfigManager projectConfigManager;
+        private OptimizelyConfigManager optimizelyConfigManager;
         private UserProfileService userProfileService;
         private NotificationCenter notificationCenter;
 
@@ -1155,6 +1167,12 @@ public Optimizely build() {
                 projectConfigManager = fallbackConfigManager;
             }
 
+            // PollingProjectConfigManager now also implements OptimizelyConfigManager interface to support OptimizelyConfig API.
+            // This check is needed in case a consumer provides their own ProjectConfigManager which does nt implement OptimizelyConfigManager interface
+            if (projectConfigManager instanceof OptimizelyConfigManager) {
+                optimizelyConfigManager = (OptimizelyConfigManager) projectConfigManager;
+            }
+
             if (notificationCenter == null) {
                 notificationCenter = new NotificationCenter();
             }
@@ -1164,7 +1182,7 @@ public Optimizely build() {
                 eventProcessor = new ForwardingEventProcessor(eventHandler, notificationCenter);
             }
 
-            return new Optimizely(eventHandler, eventProcessor, errorHandler, decisionService, userProfileService, projectConfigManager, notificationCenter);
+            return new Optimizely(eventHandler, eventProcessor, errorHandler, decisionService, userProfileService, projectConfigManager, optimizelyConfigManager, notificationCenter);
         }
     }
 }

core-api/src/main/java/com/optimizely/ab/config/PollingProjectConfigManager.java

@@ -1,6 +1,6 @@
 /**
  *
- *    Copyright 2019, Optimizely and contributors
+ *    Copyright 2019-2020, Optimizely and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -18,6 +18,9 @@
 
 import com.optimizely.ab.notification.NotificationCenter;
 import com.optimizely.ab.notification.UpdateConfigNotification;
+import com.optimizely.ab.optimizelyconfig.OptimizelyConfig;
+import com.optimizely.ab.optimizelyconfig.OptimizelyConfigManager;
+import com.optimizely.ab.optimizelyconfig.OptimizelyConfigService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -37,12 +40,13 @@
  * is initially set. A default ProjectConfig can be provided to bootstrap the initial ProjectConfig
  * return value and prevent blocking.
  */
-public abstract class PollingProjectConfigManager implements ProjectConfigManager, AutoCloseable {
+public abstract class PollingProjectConfigManager implements ProjectConfigManager, AutoCloseable, OptimizelyConfigManager {
 
     private static final Logger logger = LoggerFactory.getLogger(PollingProjectConfigManager.class);
     private static final UpdateConfigNotification SIGNAL = new UpdateConfigNotification();
 
     private final AtomicReference<ProjectConfig> currentProjectConfig = new AtomicReference<>();
+    private final AtomicReference<OptimizelyConfig> currentOptimizelyConfig = new AtomicReference<>();
     private final ScheduledExecutorService scheduledExecutorService;
     private final long period;
     private final TimeUnit timeUnit;
@@ -99,6 +103,7 @@ void setConfig(ProjectConfig projectConfig) {
         logger.info("New datafile set with revision: {}. Old revision: {}", projectConfig.getRevision(), previousRevision);
 
         currentProjectConfig.set(projectConfig);
+        currentOptimizelyConfig.set(new OptimizelyConfigService(projectConfig).getConfig());
         countDownLatch.countDown();
         notificationCenter.send(SIGNAL);
     }
@@ -132,6 +137,15 @@ public ProjectConfig getConfig() {
         return projectConfig == null ? currentProjectConfig.get() : projectConfig;
     }
 
+    /**
+     * Returns the cached {@link OptimizelyConfig}
+     * @return {@link OptimizelyConfig}
+     */
+    @Override
+    public OptimizelyConfig getOptimizelyConfig() {
+        return currentOptimizelyConfig.get();
+    }
+
     public synchronized void start() {
         if (started) {
             logger.warn("Manager already started.");

core-api/src/main/java/com/optimizely/ab/optimizelyconfig/OptimizelyConfig.java

@@ -45,4 +45,21 @@ public Map<String, OptimizelyFeature> getFeaturesMap() {
     public String getRevision() {
         return revision;
     }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == null || getClass() != obj.getClass()) return false;
+        if (obj == this) return true;
+        OptimizelyConfig optimizelyConfig = (OptimizelyConfig) obj;
+        return revision.equals(optimizelyConfig.getRevision()) &&
+            experimentsMap.equals(optimizelyConfig.getExperimentsMap()) &&
+            featuresMap.equals(optimizelyConfig.getFeaturesMap());
+    }
+
+    @Override
+    public int hashCode() {
+        int hash = revision.hashCode();
+        hash = 31 * hash + experimentsMap.hashCode();
+        return hash;
+    }
 }

core-api/src/main/java/com/optimizely/ab/optimizelyconfig/OptimizelyConfigManager.java

@@ -0,0 +1,26 @@
+/**
+ *
+ *    Copyright 2020, Optimizely and contributors
+ *
+ *    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
+ *
+ *        http://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 com.optimizely.ab.optimizelyconfig;
+
+public interface OptimizelyConfigManager {
+    /**
+     * Implementations of this method should return {@link OptimizelyConfig}
+     *
+     * @return {@link OptimizelyConfig}
+     */
+    OptimizelyConfig getOptimizelyConfig();
+}

core-api/src/test/java/com/optimizely/ab/config/PollingProjectConfigManagerTest.java

@@ -1,6 +1,6 @@
 /**
  *
- *    Copyright 2019, Optimizely and contributors
+ *    Copyright 2019-2020, Optimizely and contributors
  *
  *    Licensed under the Apache License, Version 2.0 (the "License");
  *    you may not use this file except in compliance with the License.
@@ -150,6 +150,26 @@ public ProjectConfig poll() {
         assertEquals(newerProjectConfig, testProjectConfigManager.getConfig());
     }
 
+    @Test
+    public void testSetOptimizelyConfig(){
+        assertNull(testProjectConfigManager.getOptimizelyConfig());
+
+        testProjectConfigManager.setConfig(projectConfig);
+        assertEquals("1480511547", testProjectConfigManager.getOptimizelyConfig().getRevision());
+
+        // cached config because project config is null
+        testProjectConfigManager.setConfig(null);
+        assertEquals("1480511547", testProjectConfigManager.getOptimizelyConfig().getRevision());
+
+        // created config with new revision
+        ProjectConfig newerProjectConfig = mock(ProjectConfig.class);
+        when(newerProjectConfig.getRevision()).thenReturn("new");
+
+        // verify the new optimizely config
+        testProjectConfigManager.setConfig(newerProjectConfig);
+        assertEquals("new", testProjectConfigManager.getOptimizelyConfig().getRevision());
+    }
+
     @Test
     public void testErroringProjectConfigManagerWithTimeout() throws Exception {
         testProjectConfigManager = new TestProjectConfigManager() {