CDS: Implement front-end support for local transactions

[controller.git] / opendaylight / md-sal / sal-distributed-datastore / src / main / java / org / opendaylight / controller / cluster / datastore / TransactionContextCleanup.java

diff --git a/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/TransactionContextCleanup.java b/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/TransactionContextCleanup.java
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+++ b/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/TransactionContextCleanup.java
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+/*
+ * Copyright (c) 2015 Brocade Communications Systems, Inc. and others.  All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.controller.cluster.datastore;
+
+import com.google.common.base.FinalizablePhantomReference;
+import com.google.common.base.FinalizableReferenceQueue;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A PhantomReference that closes remote transactions for a TransactionContext when it's
+ * garbage collected. This is used for read-only transactions as they're not explicitly closed
+ * by clients. So the only way to detect that a transaction is no longer in use and it's safe
+ * to clean up is when it's garbage collected. It's inexact as to when an instance will be GC'ed
+ * but TransactionProxy instances should generally be short-lived enough to avoid being moved
+ * to the old generation space and thus should be cleaned up in a timely manner as the GC
+ * runs on the young generation (eden, swap1...) space much more frequently.
+ */
+final class TransactionContextCleanup extends FinalizablePhantomReference<RemoteTransactionContextSupport> {
+    private static final Logger LOG = LoggerFactory.getLogger(TransactionContextCleanup.class);
+    /**
+     * Used to enqueue the PhantomReferences for read-only TransactionProxy instances. The
+     * FinalizableReferenceQueue is safe to use statically in an OSGi environment as it uses some
+     * trickery to clean up its internal thread when the bundle is unloaded.
+     */
+    private static final FinalizableReferenceQueue QUEUE = new FinalizableReferenceQueue();
+
+    /**
+     * This stores the TransactionProxyCleanupPhantomReference instances statically, This is
+     * necessary because PhantomReferences need a hard reference so they're not garbage collected.
+     * Once finalized, the TransactionProxyCleanupPhantomReference removes itself from this map
+     * and thus becomes eligible for garbage collection.
+     */
+    private static final Map<TransactionContext, TransactionContextCleanup> CACHE = new ConcurrentHashMap<>();
+
+    private final TransactionContext cleanup;
+
+    private TransactionContextCleanup(RemoteTransactionContextSupport referent, TransactionContext cleanup) {
+        super(referent, QUEUE);
+        this.cleanup = cleanup;
+    }
+
+    static void track(final RemoteTransactionContextSupport referent, final TransactionContext cleanup) {
+        final TransactionContextCleanup ret = new TransactionContextCleanup(referent, cleanup);
+        CACHE.put(cleanup, ret);
+    }
+
+    @Override
+    public void finalizeReferent() {
+        LOG.trace("Cleaning up {} Tx actors {}", cleanup);
+
+        if (CACHE.remove(cleanup) != null) {
+            cleanup.closeTransaction();
+        }
+    }
+
+    static void untrack(final RemoteTransactionContext cleanup) {
+        CACHE.remove(cleanup);
+    }
+}
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