[FFM-1844]: FeatureSnapshot for JavaSDK (#199)

Added ability to store and retrieve feature snapshot, containing both previous and current version of the feature config.

Author: akiraqb

README.md

@@ -78,14 +78,14 @@ Add the following Maven dependency in your project's pom.xml file:
 <dependency>
     <groupId>io.harness</groupId>
     <artifactId>ff-java-server-sdk</artifactId>
-    <version>1.6.1</version>
+    <version>1.7.0</version>
 </dependency>
 ```
 
 #### Gradle
 
 ```
-implementation 'io.harness:ff-java-server-sdk:1.6.1'
+implementation 'io.harness:ff-java-server-sdk:1.7.0'
 ```
 
 ### Code Sample

build.gradle

@@ -18,6 +18,7 @@ plugins {
     id 'jacoco-report-aggregation'
     id "com.github.spotbugs" version libs.versions.spotbugs
     id "org.owasp.dependencycheck" version libs.versions.depcheck
+    id 'me.champeau.jmh' version '0.6.8' // Added JMH plugin
 }
 
 
@@ -55,6 +56,10 @@ dependencies {
 
     compileOnly libs.lombok
     annotationProcessor libs.lombok
+
+    // JMH dependencies
+    implementation 'org.openjdk.jmh:jmh-core:1.37'
+    annotationProcessor 'org.openjdk.jmh:jmh-generator-annprocess:1.37'
 }
 
 group = 'io.harness'

examples/build.gradle

@@ -18,3 +18,13 @@ tasks.register('GettingStarted', JavaExec) {
     classpath = sourceSets.main.runtimeClasspath
     mainClass = "io.harness.ff.examples.GettingStarted"
 }
+
+tasks.register('EventExample', JavaExec) {
+    classpath = sourceSets.main.runtimeClasspath
+    mainClass = "io.harness.ff.examples.EventExample"
+}
+
+tasks.register('EventExampleWithFeatureSnapshot', JavaExec) {
+    classpath = sourceSets.main.runtimeClasspath
+    mainClass = "io.harness.ff.examples.EventExampleWithFeatureSnapshot"
+}

examples/src/main/java/io/harness/ff/examples/EventExampleWithFeatureSnapshot.java

@@ -0,0 +1,106 @@
+package io.harness.ff.examples;
+
+import io.harness.cf.client.api.BaseConfig;
+import io.harness.cf.client.api.CfClient;
+import io.harness.cf.client.api.Event;
+import io.harness.cf.client.api.XmlFileMapStore;
+import io.harness.cf.client.connector.HarnessConfig;
+import io.harness.cf.client.connector.HarnessConnector;
+import io.harness.cf.client.dto.Target;
+import io.harness.cf.model.FeatureSnapshot;
+import lombok.extern.slf4j.Slf4j;
+
+import java.util.List;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+@Slf4j
+public class EventExampleWithFeatureSnapshot {
+    private static final String SDK_KEY = "";
+    private static final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
+
+    private static CfClient client;
+
+    public static void main(String... args) {
+
+        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
+            scheduler.shutdown();
+            client.close();
+        }));
+
+        final XmlFileMapStore fileStore = new XmlFileMapStore("Non-Freemium");
+        // this is one way of initialising config.
+        final HarnessConnector hc = new HarnessConnector(SDK_KEY, HarnessConfig.builder().build());
+
+        BaseConfig bc = BaseConfig.builder().
+                enableFeatureSnapshot(true).build();
+
+        // initialise the client.
+        client = new CfClient(hc, bc);
+
+        client.on(Event.READY, result -> log.info("READY"));
+
+        // example: specified prefix we can filter on.
+        final String FLAG_PREFIX = "FFM_";
+        // example:  given flag change event - get both previous and current feature if prefix is matched.
+        client.on(Event.CHANGED, identifier -> {
+            if (identifier.startsWith(FLAG_PREFIX)) {
+                getSnapshot(identifier);
+            } else {
+                log.info("We had an event change but flag did not have required prefix");
+            }
+        });
+
+        // example : given flag change event - get all snapshots.
+        client.on(Event.CHANGED, identifier -> {
+            getAllSnapshots();
+        });
+
+        // example : given flag change event - get all snapshots with given prefix.
+        client.on(Event.CHANGED, identifier -> {
+            getAllSnapshotsWithPrefix();
+        });
+
+        final Target target = Target.builder().identifier("target1").attribute("testKey", "TestValue").name("target1").build();
+
+        scheduler.scheduleAtFixedRate(() -> {
+            log.info("ticking...");
+        }, 0, 10, TimeUnit.SECONDS);
+
+    }
+
+
+    // example method to extract a single snapshot.
+    private static void getSnapshot(String identifier) {
+        log.info("We had a chang event and prefix matched, lets inspect the diff");
+        // fetch current and previous version of the feature
+        FeatureSnapshot snapshot = client.getFeatureSnapshot(identifier);
+        log.info("Previous flag config: {}, {}", identifier, snapshot.getPrevious());
+        log.info("Current flag config: {}, {}", identifier, snapshot.getCurrent());
+    }
+
+
+    // example method to extract and print all the snapshots.
+    private static void getAllSnapshots() {
+        // get all snapshots
+        List<FeatureSnapshot> snapshots = client.getAllFeatureSnapshots();
+        int counter = 0;
+        for (FeatureSnapshot snapshot : snapshots) {
+            log.info("snapshots {} {}", ++counter, snapshot);
+        }
+    }
+
+    // example method to extract and print all the snapshots.
+    private static void getAllSnapshotsWithPrefix() {
+        // get all snapshots
+        String prefix = "FFM_";
+        List<FeatureSnapshot> snapshots = client.getAllFeatureSnapshots(prefix);
+        int counter = 0;
+        for (FeatureSnapshot snapshot : snapshots) {
+            log.info("snapshots {} {}", ++counter, snapshot);
+        }
+    }
+}
+
+

settings.gradle

@@ -4,7 +4,7 @@ dependencyResolutionManagement {
     versionCatalogs {
         libs {
             // main sdk version
-            version('sdk', '1.6.1');
+            version('sdk', '1.7.0');
 
             // sdk deps
             version('okhttp3', '4.12.0')

src/main/java/io/harness/cf/client/api/BaseConfig.java

@@ -42,6 +42,9 @@ public class BaseConfig {
   /** If metrics service POST call is taking > this time, we need to know about it */
   @Builder.Default private final long metricsServiceAcceptableDuration = 10000;
 
+  /** store previous and current version of the FeatureConfig */
+  @Builder.Default private final boolean enableFeatureSnapshot = false;
+
   /** Get metrics post frequency in seconds */
   public int getFrequency() {
     return Math.max(frequency, Config.MIN_FREQUENCY);

src/main/java/io/harness/cf/client/api/CfClient.java

@@ -5,6 +5,8 @@
 import io.harness.cf.client.dto.Message;
 import io.harness.cf.client.dto.Target;
 import io.harness.cf.client.logger.LogUtil;
+import io.harness.cf.model.FeatureSnapshot;
+import java.util.List;
 import java.util.function.Consumer;
 import lombok.NonNull;
 
@@ -83,6 +85,18 @@ public void on(@NonNull final Event event, @NonNull final Consumer<String> consu
     client.on(event, consumer);
   }
 
+  public List<FeatureSnapshot> getAllFeatureSnapshots(String prefix) {
+    return client.getFeatureSnapshots(prefix);
+  }
+
+  public List<FeatureSnapshot> getAllFeatureSnapshots() {
+    return client.getFeatureSnapshots();
+  }
+
+  public FeatureSnapshot getFeatureSnapshot(@NonNull String identifier) {
+    return client.getFeatureSnapshot(identifier);
+  }
+
   public void off() {
     client.off();
   }

src/main/java/io/harness/cf/client/api/InnerClient.java

@@ -6,7 +6,10 @@
 import io.harness.cf.client.dto.Message;
 import io.harness.cf.client.dto.Target;
 import io.harness.cf.model.FeatureConfig;
+import io.harness.cf.model.FeatureSnapshot;
 import io.harness.cf.model.Variation;
+import java.util.LinkedList;
+import java.util.List;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Consumer;
@@ -86,7 +89,9 @@ protected void setUp(@NonNull final Connector connector, @NonNull final BaseConf
     this.connector.setOnUnauthorized(this::onUnauthorized);
 
     // initialization
-    repository = new StorageRepository(options.getCache(), options.getStore(), this);
+    repository =
+        new StorageRepository(
+            options.getCache(), options.getStore(), this, options.isEnableFeatureSnapshot());
     evaluator = new Evaluator(repository, options);
     authService = new AuthService(this.connector, options.getPollIntervalInSeconds(), this);
     pollProcessor =
@@ -307,6 +312,32 @@ public synchronized void waitForInitialization()
     }
   }
 
+  public List<FeatureSnapshot> getFeatureSnapshots() {
+    return getFeatureSnapshots("");
+  }
+
+  public List<FeatureSnapshot> getFeatureSnapshots(String prefix) {
+    if (!options.isEnableFeatureSnapshot()) {
+      log.debug("FeatureSnapshot disabled, snapshot will contain only current version.");
+    }
+    List<String> identifiers = repository.getAllFeatureIdentifiers(prefix);
+    List<FeatureSnapshot> snapshots = new LinkedList<>();
+
+    for (String identifier : identifiers) {
+      FeatureSnapshot snapshot = getFeatureSnapshot(identifier);
+      snapshots.add(snapshot);
+    }
+
+    return snapshots;
+  }
+
+  public FeatureSnapshot getFeatureSnapshot(@NonNull String identifier) {
+    if (!options.isEnableFeatureSnapshot()) {
+      log.debug("FeatureSnapshot disabled, snapshot will contain only current version.");
+    }
+    return repository.getFeatureSnapshot(identifier);
+  }
+
   public void on(@NonNull final Event event, @NonNull final Consumer<String> consumer) {
     final CopyOnWriteArrayList<Consumer<String>> consumers =
         events.getOrDefault(event, new CopyOnWriteArrayList<>());

src/main/java/io/harness/cf/client/api/Query.java

@@ -1,6 +1,7 @@
 package io.harness.cf.client.api;
 
 import io.harness.cf.model.FeatureConfig;
+import io.harness.cf.model.FeatureSnapshot;
 import io.harness.cf.model.Segment;
 import java.util.List;
 import java.util.Optional;
@@ -13,4 +14,8 @@ public interface Query {
   Optional<Segment> getSegment(@NonNull String identifier);
 
   List<String> findFlagsBySegment(@NonNull String identifier);
+
+  FeatureSnapshot getFeatureSnapshot(@NonNull String identifier);
+
+  List<String> getAllFeatureIdentifiers(String prefix);
 }