DefaultSnapshotter.java

/** 
 *  Copyright (c) 2015 The original author or authors
 *
 *  Licensed 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.reveno.atp.core.snapshots;

import org.reveno.atp.api.RepositorySnapshotter;
import org.reveno.atp.api.domain.RepositoryData;
import org.reveno.atp.core.api.channel.Channel;
import org.reveno.atp.core.api.serialization.RepositoryDataSerializer;
import org.reveno.atp.core.api.storage.SnapshotStorage;
import org.reveno.atp.core.api.storage.SnapshotStorage.SnapshotStore;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class DefaultSnapshotter implements RepositorySnapshotter {
	
	@Override
	public SnapshotIdentifier lastSnapshot() {
		return storage.getLastSnapshotStore();
	}

	@Override
	public long lastJournalVersionSnapshotted() {
		SnapshotStore store = storage.getLastSnapshotStore();
		return store == null ? -1 : store.getLastJournalVersion();
	}

	@Override
	public SnapshotIdentifier prepare() {
		SnapshotIdentifier si = storage.nextTempSnapshotStore();
		LOG.debug("Prepared default snapshot {}", si);
		return si;
	}

	@Override
	public void commit(long lastJournalVersion, SnapshotIdentifier identifier) {
		if (identifier.getType() != SnapshotStore.TYPE) {
			LOG.error("Wrong snapshot identifier type!");
			return;
		}
		SnapshotStore snap = (SnapshotStore) identifier;
		storage.move(snap, storage.nextSnapshotAfter(lastJournalVersion));
		LOG.debug("Moved default repository snapshot {}", snap);
	}

	@Override
	public void snapshot(RepositoryData repo, SnapshotIdentifier identifier) {
		if (identifier.getType() != SnapshotStore.TYPE) {
			LOG.error("Wrong snapshot identifier type!");
			return;
		}
		SnapshotStore snap = (SnapshotStore) identifier;
		for (int i = 0; i < serializers.length; i++) {
			try (Channel c = storage.snapshotChannel(snap.getSnapshotPath())) {
				LOG.debug("Performing default repository snapshot to {}", snap);

				final int index = i;
				c.write(b -> serializers[index].serialize(repo, b), true);
			} catch (Throwable t) {
				if (i + 1 == serializers.length) {
					throw new RuntimeException(t);
				} else {
					LOG.info("Can't snapshot with {}, falling back to {}", serializers[i].getClass().getSimpleName(),
							serializers[i + 1].getClass().getSimpleName());
					storage.removeSnapshotStore(snap);
					SnapshotStore nextStore = storage.nextTempSnapshotStore();
					snap.setSnapshotPath(nextStore.getSnapshotPath());
				}
				continue;
			}
			break;
		}
	}

	@Override
	public RepositoryData load() {
		if (storage.getLastSnapshotStore() == null)
			return null;
		
		SnapshotStore snap = storage.getLastSnapshotStore();
		for (RepositoryDataSerializer serializer : serializers) {
			try (Channel c = storage.snapshotChannel(snap.getSnapshotPath())) {
				LOG.debug("Loading repository snapshot from {}", snap);

				return serializer.deserialize(c.read());
			} catch (Throwable ignored) {
			} finally {
				LOG.debug("Loaded repository snapshot from {}", snap);
			}
		}
		return null;
	}

	public DefaultSnapshotter(
			SnapshotStorage storage,
			RepositoryDataSerializer... serializers) {
		this.storage = storage;
		this.serializers = serializers;
	}

	
	protected final SnapshotStorage storage;
	protected final RepositoryDataSerializer[] serializers;
	protected static final Logger LOG = LoggerFactory.getLogger(DefaultSnapshotter.class);

}