Fix java leases usage from java and scala #28685

Leases are always stored as a ScalaLease and the Java LeaseProvider
unwraps the adapter.

It is important that the same lease can be used from java and scala for
mixed langugae code bases.

akka-coordination/src/main/mima-filters/2.6.4.backwards.excludes

@@ -0,0 +1,2 @@
+# Wasn't meant for user extension
+ProblemFilters.exclude[FinalClassProblem]("akka.coordination.lease.scaladsl.LeaseProvider")

akka-coordination/src/main/scala/akka/coordination/lease/internal/LeaseAdapter.scala

@@ -10,18 +10,19 @@ import java.util.function.Consumer
 
 import akka.annotation.InternalApi
 import akka.coordination.lease.LeaseSettings
-import akka.coordination.lease.javadsl.Lease
 import akka.coordination.lease.scaladsl.{ Lease => ScalaLease }
+import akka.coordination.lease.javadsl.{ Lease => JavaLease }
 
 import scala.compat.java8.FutureConverters._
 import scala.compat.java8.OptionConverters._
 import scala.concurrent.ExecutionContext
+import scala.concurrent.Future
 
 /**
  * INTERNAL API
  */
 @InternalApi
-final private[akka] class LeaseAdapter(delegate: ScalaLease)(implicit val ec: ExecutionContext) extends Lease {
+final private[akka] class LeaseAdapter(delegate: ScalaLease)(implicit val ec: ExecutionContext) extends JavaLease {
 
   override def acquire(): CompletionStage[java.lang.Boolean] = delegate.acquire().map(Boolean.box).toJava
 
@@ -33,3 +34,23 @@ final private[akka] class LeaseAdapter(delegate: ScalaLease)(implicit val ec: Ex
   override def checkLease(): Boolean = delegate.checkLease()
   override def getSettings(): LeaseSettings = delegate.settings
 }
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+final private[akka] class LeaseAdapterToScala(val delegate: JavaLease)(implicit val ec: ExecutionContext)
+    extends ScalaLease(delegate.getSettings()) {
+
+  override def acquire(): Future[Boolean] =
+    delegate.acquire().toScala.map(Boolean.unbox)
+
+  override def acquire(leaseLostCallback: Option[Throwable] => Unit): Future[Boolean] =
+    delegate.acquire(o => leaseLostCallback(o.asScala)).toScala.map(Boolean.unbox)
+
+  override def release(): Future[Boolean] =
+    delegate.release().toScala.map(Boolean.unbox)
+
+  override def checkLease(): Boolean =
+    delegate.checkLease()
+}

akka-coordination/src/main/scala/akka/coordination/lease/javadsl/LeaseProvider.scala

@@ -7,6 +7,7 @@ package akka.coordination.lease.javadsl
 import akka.actor.ClassicActorSystemProvider
 import akka.actor.{ ActorSystem, ExtendedActorSystem, Extension, ExtensionId, ExtensionIdProvider }
 import akka.coordination.lease.internal.LeaseAdapter
+import akka.coordination.lease.internal.LeaseAdapterToScala
 import akka.coordination.lease.scaladsl.{ LeaseProvider => ScalaLeaseProvider }
 
 object LeaseProvider extends ExtensionId[LeaseProvider] with ExtensionIdProvider {
@@ -35,6 +36,10 @@ class LeaseProvider(system: ExtendedActorSystem) extends Extension {
    */
   def getLease(leaseName: String, configPath: String, ownerName: String): Lease = {
     val scalaLease = delegate.getLease(leaseName, configPath, ownerName)
-    new LeaseAdapter(scalaLease)(system.dispatchers.internalDispatcher)
+    // unwrap if this is a java implementation
+    scalaLease match {
+      case adapter: LeaseAdapterToScala => adapter.delegate
+      case _                            => new LeaseAdapter(scalaLease)(system.dispatchers.internalDispatcher)
+    }
   }
 }

akka-coordination/src/main/scala/akka/coordination/lease/scaladsl/LeaseProvider.scala

@@ -17,6 +17,9 @@ import akka.actor.ExtensionId
 import akka.actor.ExtensionIdProvider
 import akka.event.Logging
 import akka.coordination.lease.LeaseSettings
+import akka.coordination.lease.internal.LeaseAdapterToScala
+
+import scala.reflect.ClassTag
 
 object LeaseProvider extends ExtensionId[LeaseProvider] with ExtensionIdProvider {
   override def get(system: ActorSystem): LeaseProvider = super.get(system)
@@ -29,7 +32,7 @@ object LeaseProvider extends ExtensionId[LeaseProvider] with ExtensionIdProvider
   private final case class LeaseKey(leaseName: String, configPath: String, clientName: String)
 }
 
-class LeaseProvider(system: ExtendedActorSystem) extends Extension {
+final class LeaseProvider(system: ExtendedActorSystem) extends Extension {
   import LeaseProvider.LeaseKey
 
   private val log = Logging(system, getClass)
@@ -46,6 +49,10 @@ class LeaseProvider(system: ExtendedActorSystem) extends Extension {
    * @param ownerName the owner that will `acquire` the lease, e.g. hostname and port of the ActorSystem
    */
   def getLease(leaseName: String, configPath: String, ownerName: String): Lease = {
+    internalGetLease(leaseName, configPath, ownerName)
+  }
+
+  private[akka] def internalGetLease(leaseName: String, configPath: String, ownerName: String): Lease = {
     val leaseKey = LeaseKey(leaseName, configPath, ownerName)
     leases.computeIfAbsent(
       leaseKey,
@@ -54,39 +61,54 @@ class LeaseProvider(system: ExtendedActorSystem) extends Extension {
           val leaseConfig = system.settings.config
             .getConfig(configPath)
             .withFallback(system.settings.config.getConfig("akka.coordination.lease"))
-          loadLease(LeaseSettings(leaseConfig, leaseName, ownerName), configPath)
+
+          val settings = LeaseSettings(leaseConfig, leaseName, ownerName)
+
+          // Try and load a scala implementation
+          val lease: Try[Lease] =
+            loadLease[Lease](settings).recoverWith {
+              case _: ClassCastException =>
+                // Try and load a java implementation
+                loadLease[akka.coordination.lease.javadsl.Lease](settings).map(javaLease =>
+                  new LeaseAdapterToScala(javaLease)(system.dispatchers.internalDispatcher))
+            }
+
+          lease match {
+            case Success(value) => value
+            case Failure(e) =>
+              log.error(
+                e,
+                "Invalid lease configuration for leaseName [{}], configPath [{}] lease-class [{}]. " +
+                "The class must implement scaladsl.Lease or javadsl.Lease and have constructor with LeaseSettings parameter and " +
+                "optionally ActorSystem parameter.",
+                settings.leaseName,
+                configPath,
+                settings.leaseConfig.getString("lease-class"))
+              throw e
+          }
         }
       })
   }
 
-  private def loadLease(leaseSettings: LeaseSettings, configPath: String): Lease = {
+  /**
+   * The Lease types are separate for Java and Scala and A java lease needs to be loadable
+   * from Scala and vice versa as leases can be in libraries and user should not care what
+   * language it is implemented in.
+   */
+  private def loadLease[T: ClassTag](leaseSettings: LeaseSettings): Try[T] = {
     val fqcn = leaseSettings.leaseConfig.getString("lease-class")
     require(fqcn.nonEmpty, "lease-class must not be empty")
     val dynamicAccess = system.dynamicAccess
-    val instance: Try[Lease] = dynamicAccess.createInstanceFor[Lease](
+    dynamicAccess.createInstanceFor[T](
       fqcn,
       immutable.Seq((classOf[LeaseSettings], leaseSettings), (classOf[ExtendedActorSystem], system))) match {
-      case s: Success[Lease] =>
+      case s: Success[T] =>
         s
       case Failure(_: NoSuchMethodException) =>
-        dynamicAccess.createInstanceFor[Lease](fqcn, immutable.Seq((classOf[LeaseSettings], leaseSettings)))
+        dynamicAccess.createInstanceFor[T](fqcn, immutable.Seq((classOf[LeaseSettings], leaseSettings)))
       case f: Failure[_] =>
         f
     }
-    instance match {
-      case Success(value) => value
-      case Failure(e) =>
-        log.error(
-          e,
-          "Invalid lease configuration for leaseName [{}], configPath [{}] lease-class [{}]. " +
-          "The class must implement Lease and have constructor with LeaseSettings parameter and " +
-          "optionally ActorSystem parameter.",
-          leaseSettings.leaseName,
-          configPath,
-          fqcn)
-        throw e
-    }
-  }
 
-  // TODO how to clean up a lease? Not important for this use case as we'll only have one lease
+  }
 }

akka-coordination/src/test/java/jdocs/akka/coordination/lease/LeaseDocTest.java

@@ -5,7 +5,6 @@
 package jdocs.akka.coordination.lease;
 
 import akka.actor.ActorSystem;
-import akka.cluster.Cluster;
 import akka.coordination.lease.LeaseSettings;
 import akka.coordination.lease.javadsl.Lease;
 import akka.coordination.lease.javadsl.LeaseProvider;
@@ -14,13 +13,15 @@ import docs.akka.coordination.LeaseDocSpec;
 import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;
+import org.scalatestplus.junit.JUnitSuite;
 
 import java.util.Optional;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionStage;
 import java.util.function.Consumer;
 
 @SuppressWarnings("unused")
-public class LeaseDocTest {
+public class LeaseDocTest extends JUnitSuite {
   // #lease-example
   static class SampleLease extends Lease {
 
@@ -37,22 +38,22 @@ public class LeaseDocTest {
 
     @Override
     public CompletionStage<Boolean> acquire() {
-      return null;
+      return CompletableFuture.completedFuture(true);
     }
 
     @Override
     public CompletionStage<Boolean> acquire(Consumer<Optional<Throwable>> leaseLostCallback) {
-      return null;
+      return CompletableFuture.completedFuture(true);
     }
 
     @Override
     public CompletionStage<Boolean> release() {
-      return null;
+      return CompletableFuture.completedFuture(true);
     }
 
     @Override
     public boolean checkLease() {
-      return false;
+      return true;
     }
   }
   // #lease-example
@@ -73,10 +74,10 @@ public class LeaseDocTest {
   private void doSomethingImportant(Optional<Throwable> leaseLostReason) {}
 
   @Test
-  public void beLoadable() {
+  public void javaLeaseBeLoadableFromJava() {
     // #lease-usage
     Lease lease =
-        LeaseProvider.get(system).getLease("<name of the lease>", "docs-lease", "<owner name>");
+        LeaseProvider.get(system).getLease("<name of the lease>", "jdocs-lease", "<owner name>");
     CompletionStage<Boolean> acquired = lease.acquire();
     boolean stillAcquired = lease.checkLease();
     CompletionStage<Boolean> released = lease.release();
@@ -87,8 +88,18 @@ public class LeaseDocTest {
     // #lost-callback
 
     // #cluster-owner
-    String owner = Cluster.get(system).selfAddress().hostPort();
+    // String owner = Cluster.get(system).selfAddress().hostPort();
     // #cluster-owner
 
   }
+
+  @Test
+  public void scalaLeaseBeLoadableFromJava() {
+    Lease lease =
+        LeaseProvider.get(system).getLease("<name of the lease>", "docs-lease", "<owner name>");
+    CompletionStage<Boolean> acquired = lease.acquire();
+    boolean stillAcquired = lease.checkLease();
+    CompletionStage<Boolean> released = lease.release();
+    lease.acquire(this::doSomethingImportant);
+  }
 }

akka-coordination/src/test/scala/docs/akka/coordination/LeaseDocSpec.scala

@@ -35,7 +35,9 @@ class SampleLease(settings: LeaseSettings) extends Lease(settings) {
 
 object LeaseDocSpec {
 
-  val config = ConfigFactory.parseString("""
+  def config() =
+    ConfigFactory.parseString("""
+      jdocs-lease.lease-class = "jdocs.akka.coordination.lease.LeaseDocTest$SampleLease"
       #lease-config
       akka.actor.provider = cluster
       docs-lease {
@@ -62,7 +64,7 @@ class LeaseDocSpec extends AkkaSpec(LeaseDocSpec.config) {
   import LeaseDocSpec._
 
   "A docs lease" should {
-    "be loadable" in {
+    "scala lease be loadable from scala" in {
 
       //#lease-usage
       val lease = LeaseProvider(system).getLease("<name of the lease>", "docs-lease", "owner")
@@ -83,6 +85,16 @@ class LeaseDocSpec extends AkkaSpec(LeaseDocSpec.config) {
       blackhole(acquired, stillAcquired, released, owner)
 
     }
+
+    "java lease be loadable from scala" in {
+      val lease = LeaseProvider(system).getLease("<name of the lease>", "jdocs-lease", "owner")
+      val acquired: Future[Boolean] = lease.acquire()
+      val stillAcquired: Boolean = lease.checkLease()
+      val released: Future[Boolean] = lease.release()
+      lease.acquire(leaseLostReason => doSomethingImportant(leaseLostReason))
+
+      blackhole(acquired, stillAcquired, released)
+    }
   }
 
 }