Allow SnapshotBackedReadTransaction customization
[controller.git] / opendaylight / md-sal / sal-dom-spi / src / main / java / org / opendaylight / controller / sal / core / spi / data / SnapshotBackedReadTransaction.java
index 8e5957c..eaf3aa7 100644 (file)
@@ -8,11 +8,13 @@
 package org.opendaylight.controller.sal.core.spi.data;
 
 import static com.google.common.base.Preconditions.checkNotNull;
+
 import com.google.common.annotations.Beta;
 import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
 import com.google.common.util.concurrent.CheckedFuture;
 import com.google.common.util.concurrent.Futures;
+import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
 import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
@@ -21,17 +23,26 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
+ * Implementation of read-only transaction backed by {@link DataTreeSnapshot}.
  *
- * Implementation of read-only transaction backed by {@link DataTreeSnapshot}
- *
+ * <p>
  * Implementation of read-only transaction backed by {@link DataTreeSnapshot}
  * which delegates most of its calls to similar methods provided by underlying snapshot.
  *
- * <T> identifier type
+ * @param <T> identifier type
  */
 @Beta
-public final class SnapshotBackedReadTransaction<T> extends AbstractDOMStoreTransaction<T> implements DOMStoreReadTransaction {
+public final class SnapshotBackedReadTransaction<T> extends AbstractDOMStoreTransaction<T>
+        implements DOMStoreReadTransaction {
     private static final Logger LOG = LoggerFactory.getLogger(SnapshotBackedReadTransaction.class);
+
+    @SuppressWarnings("rawtypes")
+    private static final AtomicReferenceFieldUpdater<SnapshotBackedReadTransaction, DataTreeSnapshot> SNAPSHOT_UPDATER =
+            AtomicReferenceFieldUpdater.newUpdater(SnapshotBackedReadTransaction.class, DataTreeSnapshot.class,
+                "stableSnapshot");
+
+    // Guarded by stableSnapshot CAS, hence it does not need to be volatile
+    private TransactionClosePrototype<T> closeImpl;
     private volatile DataTreeSnapshot stableSnapshot;
 
     /**
@@ -41,19 +52,31 @@ public final class SnapshotBackedReadTransaction<T> extends AbstractDOMStoreTran
      * @param debug Enable transaction debugging
      * @param snapshot Snapshot which will be modified.
      */
-    SnapshotBackedReadTransaction(final T identifier, final boolean debug, final DataTreeSnapshot snapshot) {
+    SnapshotBackedReadTransaction(final T identifier, final boolean debug, final DataTreeSnapshot snapshot,
+            final TransactionClosePrototype<T> closeImpl) {
         super(identifier, debug);
         this.stableSnapshot = Preconditions.checkNotNull(snapshot);
+        this.closeImpl = closeImpl;
         LOG.debug("ReadOnly Tx: {} allocated with snapshot {}", identifier, snapshot);
     }
 
     @Override
     public void close() {
+        final DataTreeSnapshot prev = SNAPSHOT_UPDATER.getAndSet(this, null);
+        if (prev == null) {
+            LOG.debug("Store transaction: {} : previously closed", getIdentifier());
+            return;
+        }
+
         LOG.debug("Store transaction: {} : Closed", getIdentifier());
-        stableSnapshot = null;
+        if (closeImpl != null) {
+            closeImpl.transactionClosed(this);
+            closeImpl = null;
+        }
     }
 
     @Override
+    @SuppressWarnings("checkstyle:IllegalCatch")
     public CheckedFuture<Optional<NormalizedNode<?,?>>, ReadFailedException> read(final YangInstanceIdentifier path) {
         LOG.debug("Tx: {} Read: {}", getIdentifier(), path);
         checkNotNull(path, "Path must not be null.");
@@ -64,8 +87,8 @@ public final class SnapshotBackedReadTransaction<T> extends AbstractDOMStoreTran
         }
 
         try {
-            return Futures.immediateCheckedFuture(snapshot.readNode(path));
-        } catch (Exception e) {
+            return Futures.immediateCheckedFuture(Optional.fromJavaUtil(snapshot.readNode(path)));
+        } catch (RuntimeException e) {
             LOG.error("Tx: {} Failed Read of {}", getIdentifier(), path, e);
             return Futures.immediateFailedCheckedFuture(new ReadFailedException("Read failed",e));
         }
@@ -82,4 +105,23 @@ public final class SnapshotBackedReadTransaction<T> extends AbstractDOMStoreTran
             return Futures.immediateFailedCheckedFuture(e);
         }
     }
+
+    /**
+     * Prototype implementation of {@link SnapshotBackedReadTransaction#close()}.
+     *
+     * <p>
+     * This class is intended to be implemented by Transaction factories responsible for allocation
+     * of {@link org.opendaylight.mdsal.dom.spi.store.SnapshotBackedReadTransaction} and
+     * providing underlying logic for applying implementation.
+     *
+     * @param <T> identifier type
+     */
+    public interface TransactionClosePrototype<T> {
+        /**
+         * Called when a transaction is closed. This is not invoked at most once for every transaction.
+         *
+         * @param tx Transaction which got closed.
+         */
+        void transactionClosed(SnapshotBackedReadTransaction<T> tx);
+    }
 }

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