| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.tephra.snapshot; |
| |
| import com.google.common.annotations.VisibleForTesting; |
| import com.google.common.base.Throwables; |
| import com.google.common.collect.Lists; |
| import com.google.common.collect.Maps; |
| import com.google.inject.Inject; |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.tephra.TxConstants; |
| import org.apache.tephra.persist.TransactionSnapshot; |
| import org.apache.tephra.persist.TransactionVisibilityState; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import java.io.IOException; |
| import java.io.InputStream; |
| import java.io.OutputStream; |
| import java.util.Arrays; |
| import java.util.List; |
| import java.util.SortedMap; |
| import javax.annotation.Nonnull; |
| |
| /** |
| * Maintains the codecs for all known versions of the transaction snapshot encoding. |
| */ |
| public class SnapshotCodecProvider implements SnapshotCodec { |
| |
| private static final Logger LOG = LoggerFactory.getLogger(SnapshotCodecProvider.class); |
| |
| private final SortedMap<Integer, SnapshotCodec> codecs = Maps.newTreeMap(); |
| |
| @Inject |
| public SnapshotCodecProvider(Configuration configuration) { |
| initialize(configuration); |
| } |
| |
| /** |
| * Register all codec specified in the configuration with this provider. |
| * There can only be one codec for a given version. |
| */ |
| private void initialize(Configuration configuration) { |
| String[] codecClassNames = configuration.getTrimmedStrings(TxConstants.Persist.CFG_TX_SNAPHOT_CODEC_CLASSES); |
| List<Class> codecClasses = Lists.newArrayList(); |
| if (codecClassNames != null) { |
| for (String clsName : codecClassNames) { |
| try { |
| codecClasses.add(Class.forName(clsName)); |
| } catch (ClassNotFoundException cnfe) { |
| LOG.warn("Unable to load class configured for " + TxConstants.Persist.CFG_TX_SNAPHOT_CODEC_CLASSES |
| + ": " + clsName, cnfe); |
| } |
| } |
| } |
| |
| if (codecClasses.size() == 0) { |
| codecClasses.addAll(Arrays.asList(TxConstants.Persist.DEFAULT_TX_SNAPHOT_CODEC_CLASSES)); |
| } |
| for (Class<?> codecClass : codecClasses) { |
| try { |
| SnapshotCodec codec = (SnapshotCodec) (codecClass.newInstance()); |
| codecs.put(codec.getVersion(), codec); |
| LOG.debug("Using snapshot codec {} for snapshots of version {}", codecClass.getName(), codec.getVersion()); |
| } catch (Exception e) { |
| LOG.warn("Error instantiating snapshot codec {}. Skipping.", codecClass.getName(), e); |
| } |
| } |
| } |
| |
| /** |
| * Retrieve the codec for a particular version of the encoding. |
| * @param version the version of interest |
| * @return the corresponding codec |
| * @throws java.lang.IllegalArgumentException if the version is not known |
| */ |
| @Nonnull |
| @VisibleForTesting |
| SnapshotCodec getCodecForVersion(int version) { |
| SnapshotCodec codec = codecs.get(version); |
| if (codec == null) { |
| throw new IllegalArgumentException(String.format("Version %d of snapshot encoding is not supported", version)); |
| } |
| return codec; |
| } |
| |
| /** |
| * Retrieve the current snapshot codec, that is, the codec with the highest known version. |
| * @return the current codec |
| * @throws java.lang.IllegalStateException if no codecs are registered |
| */ |
| private SnapshotCodec getCurrentCodec() { |
| if (codecs.isEmpty()) { |
| throw new IllegalStateException(String.format("No codecs are registered.")); |
| } |
| return codecs.get(codecs.lastKey()); |
| } |
| |
| // Return the appropriate codec for the version in InputStream |
| private SnapshotCodec getCodec(InputStream in) { |
| BinaryDecoder decoder = new BinaryDecoder(in); |
| int persistedVersion; |
| try { |
| persistedVersion = decoder.readInt(); |
| } catch (IOException e) { |
| LOG.error("Unable to read transaction state version: ", e); |
| throw Throwables.propagate(e); |
| } |
| return getCodecForVersion(persistedVersion); |
| } |
| |
| @Override |
| public int getVersion() { |
| return getCurrentCodec().getVersion(); |
| } |
| |
| @Override |
| public TransactionSnapshot decode(InputStream in) { |
| return getCodec(in).decode(in); |
| } |
| |
| @Override |
| public TransactionVisibilityState decodeTransactionVisibilityState(InputStream in) { |
| return getCodec(in).decodeTransactionVisibilityState(in); |
| } |
| |
| @Override |
| public void encode(OutputStream out, TransactionSnapshot snapshot) { |
| SnapshotCodec codec = getCurrentCodec(); |
| try { |
| new BinaryEncoder(out).writeInt(codec.getVersion()); |
| } catch (IOException e) { |
| LOG.error("Unable to write transaction state version: ", e); |
| throw Throwables.propagate(e); |
| } |
| codec.encode(out, snapshot); |
| } |
| |
| } |