BUG-5280: centralize ShardSnapshot operations

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

diff --git a/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/persisted/ShardDataTreeSnapshot.java b/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/persisted/ShardDataTreeSnapshot.java
new file mode 100644 (file)
index 0000000..ef90101
--- /dev/null
+++ b/opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/persisted/ShardDataTreeSnapshot.java
@@ -0,0 +1,110 @@
+/*
+ * Copyright (c) 2016 Cisco 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.persisted;
+
+import com.google.common.annotations.Beta;
+import java.io.ByteArrayInputStream;
+import java.io.DataInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Optional;
+import javax.annotation.Nonnull;
+import org.opendaylight.controller.cluster.datastore.utils.SerializationUtils;
+import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Abstract base class for snapshots of the ShardDataTree.
+ *
+ * @author Robert Varga
+ */
+@Beta
+public abstract class ShardDataTreeSnapshot {
+    private static final Logger LOG = LoggerFactory.getLogger(ShardDataTreeSnapshot.class);
+
+    ShardDataTreeSnapshot() {
+        // Hidden to prevent subclassing from outside of this package
+    }
+
+    public static ShardDataTreeSnapshot deserialize(final byte[] bytes) throws IOException {
+        /**
+         * Unfortunately versions prior to Boron did not include any way to evolve the snapshot format and contained
+         * only the raw data stored in the datastore. Furthermore utilities involved do not check if the array is
+         * completely consumed, which has a nasty side-effect when coupled with the fact that PayloadVersion writes
+         * a short value.
+         *
+         * Since our versions fit into a single byte, we end up writing the 0 as the first byte, which would be
+         * interpreted as 'not present' by the old snapshot format, which uses writeBoolean/readBoolean. A further
+         * complication is that readBoolean interprets any non-zero value as true, hence we cannot use a wild value
+         * to cause it to fail.
+         */
+        if (isLegacyStream(bytes)) {
+            return deserializeLegacy(bytes);
+        }
+
+        try {
+            try (final InputStream is = new ByteArrayInputStream(bytes)) {
+                try (final DataInputStream dis = new DataInputStream(is)) {
+                    final ShardDataTreeSnapshot ret = AbstractVersionedShardDataTreeSnapshot.deserialize(dis);
+
+                    // Make sure we consume all bytes, otherwise something went very wrong
+                    final int bytesLeft = dis.available();
+                    if (bytesLeft != 0) {
+                        throw new IOException("Deserialization left " + bytesLeft + " in the buffer");
+                    }
+
+
+                    return ret;
+                }
+            }
+        } catch (IOException e) {
+            LOG.debug("Failed to deserialize versioned stream, attempting pre-Lithium ProtoBuf", e);
+            return deserializeLegacy(bytes);
+        }
+    }
+
+    /**
+     * Get the root data node contained in this snapshot.
+     *
+     * @return An optional root node.
+     */
+    public abstract Optional<NormalizedNode<?, ?>> getRootNode();
+
+    /**
+     * Serialize this snapshot into a byte array for persistence.
+     *
+     * @return Serialized snapshot
+     * @throws IOException when a serialization problem occurs
+     */
+    public abstract @Nonnull byte[] serialize() throws IOException;
+
+    private static boolean isLegacyStream(final byte[] bytes) {
+        if (bytes.length < 2) {
+            // Versioned streams have at least two bytes
+            return true;
+        }
+
+        /*
+         * The stream could potentially be a versioned stream. Here we rely on the signature marker available
+         * in org.opendaylight.controller.cluster.datastore.node.utils.stream.TokenTypes.
+         *
+         * For an old stream to be this long, the first byte has to be non-zero and the second byte has to be 0xAB.
+         *
+         * For a versioned stream, that translates to at least version 427 -- giving us at least 421 further versions
+         * before this check breaks.
+         */
+        return bytes[0] != 0 && bytes[1] == (byte)0xAB;
+    }
+
+    @Deprecated
+    private static ShardDataTreeSnapshot deserializeLegacy(final byte[] bytes) {
+        return new PreBoronShardDataTreeSnapshot(SerializationUtils.deserializeNormalizedNode(bytes));
+    }
+}
+