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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.cassandra.service.snapshot;
import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.NoSuchFileException;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.UUID;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import com.google.common.annotations.VisibleForTesting;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.db.Directories;
import org.apache.cassandra.io.util.File;
import static org.apache.cassandra.db.Directories.SNAPSHOT_SUBDIR;
import static org.apache.cassandra.service.snapshot.TableSnapshot.buildSnapshotId;
/**
* Loads snapshot metadata from data directories
*/
public class SnapshotLoader
{
private static final Logger logger = LoggerFactory.getLogger(SnapshotLoader.class);
static final Pattern SNAPSHOT_DIR_PATTERN = Pattern.compile("(?\\w+)/(?\\w+)-(?[0-9a-f]{32})/snapshots/(?.+)$");
private final Collection dataDirectories;
public SnapshotLoader()
{
this(DatabaseDescriptor.getAllDataFileLocations());
}
public SnapshotLoader(String[] dataDirectories)
{
this(Arrays.stream(dataDirectories).map(File::getPath).collect(Collectors.toList()));
}
public SnapshotLoader(Collection dataDirs)
{
this.dataDirectories = dataDirs;
}
@VisibleForTesting
static class Visitor extends SimpleFileVisitor
{
private static final Pattern UUID_PATTERN = Pattern.compile("([0-9a-f]{8})([0-9a-f]{4})([0-9a-f]{4})([0-9a-f]{4})([0-9a-f]+)");
private final Map snapshots;
public Visitor(Map snapshots)
{
this.snapshots = snapshots;
}
@Override
public FileVisitResult visitFileFailed(Path file, IOException exc) throws IOException
{
// Cassandra can remove some files while traversing the tree,
// for example when SSTables are compacted while we are walking it.
// SnapshotLoader is interested only in SSTables in snapshot directories which are not compacted,
// but we need to cover these in regular table directories too.
// If listing failed but exception is NoSuchFileException, then we
// just skip it and continue with the listing.
if (exc instanceof NoSuchFileException)
return FileVisitResult.CONTINUE;
else
throw exc;
}
@Override
public FileVisitResult preVisitDirectory(Path subdir, BasicFileAttributes attrs)
{
// see CASSANDRA-18359
if (subdir.getParent() == null || subdir.getParent().getFileName() == null)
return FileVisitResult.CONTINUE;
if (subdir.getParent().getFileName().toString().equals(SNAPSHOT_SUBDIR))
{
logger.trace("Processing directory " + subdir);
Matcher snapshotDirMatcher = SNAPSHOT_DIR_PATTERN.matcher(subdir.toString());
if (snapshotDirMatcher.find())
{
try
{
loadSnapshotFromDir(snapshotDirMatcher, subdir);
}
catch (Throwable e)
{
logger.warn("Could not load snapshot from {}.", subdir, e);
}
}
return FileVisitResult.SKIP_SUBTREE;
}
return subdir.getFileName().toString().equals(Directories.BACKUPS_SUBDIR)
? FileVisitResult.SKIP_SUBTREE
: FileVisitResult.CONTINUE;
}
/**
* Given an UUID string without dashes (ie. c7e513243f0711ec9bbc0242ac130002)
* return an UUID object (ie. c7e51324-3f07-11ec-9bbc-0242ac130002)
*/
static UUID parseUUID(String uuidWithoutDashes) throws IllegalArgumentException
{
assert uuidWithoutDashes.length() == 32 && !uuidWithoutDashes.contains("-");
String dashedUUID = UUID_PATTERN.matcher(uuidWithoutDashes).replaceFirst("$1-$2-$3-$4-$5");
return UUID.fromString(dashedUUID);
}
private void loadSnapshotFromDir(Matcher snapshotDirMatcher, Path snapshotDir)
{
String keyspaceName = snapshotDirMatcher.group("keyspace");
String tableName = snapshotDirMatcher.group("tableName");
UUID tableId = parseUUID(snapshotDirMatcher.group("tableId"));
String tag = snapshotDirMatcher.group("tag");
String snapshotId = buildSnapshotId(keyspaceName, tableName, tableId, tag);
TableSnapshot.Builder builder = snapshots.computeIfAbsent(snapshotId, k -> new TableSnapshot.Builder(keyspaceName, tableName, tableId, tag));
builder.addSnapshotDir(new File(snapshotDir));
}
}
public Set loadSnapshots()
{
Map snapshots = new HashMap<>();
Visitor visitor = new Visitor(snapshots);
for (Path dataDir : dataDirectories)
{
try
{
if (new File(dataDir).exists())
Files.walkFileTree(dataDir, Collections.emptySet(), 5, visitor);
else
logger.debug("Skipping non-existing data directory {}", dataDir);
}
catch (IOException e)
{
throw new RuntimeException(String.format("Error while loading snapshots from %s", dataDir), e);
}
}
return snapshots.values().stream().map(TableSnapshot.Builder::build).collect(Collectors.toSet());
}
}