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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.db.lifecycle;
import java.io.File;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.function.Function;
import java.util.stream.Collectors;
import com.google.common.annotations.VisibleForTesting;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.io.FSError;
import org.apache.cassandra.io.util.FileUtils;
import org.apache.cassandra.utils.Throwables;
/**
* A set of log replicas. This class mostly iterates over replicas when writing or reading,
* ensuring consistency among them and hiding replication details from LogFile.
*
* @see LogReplica
* @see LogFile
*/
public class LogReplicaSet implements AutoCloseable
{
private static final Logger logger = LoggerFactory.getLogger(LogReplicaSet.class);
private final Map replicasByFile = Collections.synchronizedMap(new LinkedHashMap<>()); // TODO: Hack until we fix CASSANDRA-14554
private Collection replicas()
{
return replicasByFile.values();
}
void addReplicas(List replicas)
{
replicas.forEach(this::addReplica);
}
void addReplica(File file)
{
File directory = file.getParentFile();
assert !replicasByFile.containsKey(directory);
try
{
replicasByFile.put(directory, LogReplica.open(file));
}
catch(FSError e)
{
logger.error("Failed to open log replica {}", file, e);
FileUtils.handleFSErrorAndPropagate(e);
}
logger.trace("Added log file replica {} ", file);
}
void maybeCreateReplica(File directory, String fileName, Set records)
{
if (replicasByFile.containsKey(directory))
return;
try
{
@SuppressWarnings("resource") // LogReplicas are closed in LogReplicaSet::close
final LogReplica replica = LogReplica.create(directory, fileName);
records.forEach(replica::append);
replicasByFile.put(directory, replica);
logger.trace("Created new file replica {}", replica);
}
catch(FSError e)
{
logger.error("Failed to create log replica {}/{}", directory, fileName, e);
FileUtils.handleFSErrorAndPropagate(e);
}
}
Throwable syncDirectory(Throwable accumulate)
{
return Throwables.perform(accumulate, replicas().stream().map(s -> s::syncDirectory));
}
Throwable delete(Throwable accumulate)
{
return Throwables.perform(accumulate, replicas().stream().map(s -> s::delete));
}
private static boolean isPrefixMatch(String first, String second)
{
return first.length() >= second.length() ?
first.startsWith(second) :
second.startsWith(first);
}
boolean readRecords(Set records)
{
Map> linesByReplica = replicas().stream()
.collect(Collectors.toMap(Function.identity(),
LogReplica::readLines,
(k, v) -> {throw new IllegalStateException("Duplicated key: " + k);},
LinkedHashMap::new));
int maxNumLines = linesByReplica.values().stream().map(List::size).reduce(0, Integer::max);
for (int i = 0; i < maxNumLines; i++)
{
String firstLine = null;
boolean partial = false;
for (Map.Entry> entry : linesByReplica.entrySet())
{
List currentLines = entry.getValue();
if (i >= currentLines.size())
continue;
String currentLine = currentLines.get(i);
if (firstLine == null)
{
firstLine = currentLine;
continue;
}
if (!isPrefixMatch(firstLine, currentLine))
{ // not a prefix match
logger.error("Mismatched line in file {}: got '{}' expected '{}', giving up",
entry.getKey().getFileName(),
currentLine,
firstLine);
entry.getKey().setError(currentLine, String.format("Does not match <%s> in first replica file", firstLine));
return false;
}
if (!firstLine.equals(currentLine))
{
if (i == currentLines.size() - 1)
{ // last record, just set record as invalid and move on
logger.warn("Mismatched last line in file {}: '{}' not the same as '{}'",
entry.getKey().getFileName(),
currentLine,
firstLine);
if (currentLine.length() > firstLine.length())
firstLine = currentLine;
partial = true;
}
else
{ // mismatched entry file has more lines, giving up
logger.error("Mismatched line in file {}: got '{}' expected '{}', giving up",
entry.getKey().getFileName(),
currentLine,
firstLine);
entry.getKey().setError(currentLine, String.format("Does not match <%s> in first replica file", firstLine));
return false;
}
}
}
LogRecord record = LogRecord.make(firstLine);
if (records.contains(record))
{ // duplicate records
logger.error("Found duplicate record {} for {}, giving up", record, record.fileName());
setError(record, "Duplicated record");
return false;
}
if (partial)
record.setPartial();
records.add(record);
if (record.isFinal() && i != (maxNumLines - 1))
{ // too many final records
logger.error("Found too many lines for {}, giving up", record.fileName());
setError(record, "This record should have been the last one in all replicas");
return false;
}
}
return true;
}
void setError(LogRecord record, String error)
{
record.setError(error);
setErrorInReplicas(record);
}
void setErrorInReplicas(LogRecord record)
{
replicas().forEach(r -> r.setError(record.raw, record.error()));
}
void printContentsWithAnyErrors(StringBuilder str)
{
replicas().forEach(r -> r.printContentsWithAnyErrors(str));
}
/**
* Add the record to all the replicas: if it is a final record then we throw only if we fail to write it
* to all, otherwise we throw if we fail to write it to any file, see CASSANDRA-10421 for details
*/
void append(LogRecord record)
{
Throwable err = Throwables.perform(null, replicas().stream().map(r -> () -> r.append(record)));
if (err != null)
{
if (!record.isFinal() || err.getSuppressed().length == replicas().size() -1)
Throwables.maybeFail(err);
logger.error("Failed to add record '{}' to some replicas '{}'", record, this);
}
}
boolean exists()
{
Optional ret = replicas().stream().map(LogReplica::exists).reduce(Boolean::logicalAnd);
return ret.isPresent() ?
ret.get()
: false;
}
public void close()
{
Throwables.maybeFail(Throwables.perform(null, replicas().stream().map(r -> r::close)));
}
@Override
public String toString()
{
Optional ret = replicas().stream().map(LogReplica::toString).reduce(String::concat);
return ret.isPresent() ?
ret.get()
: "[-]";
}
String getDirectories()
{
return String.join(", ", replicas().stream().map(LogReplica::getDirectory).collect(Collectors.toList()));
}
@VisibleForTesting
List getFiles()
{
return replicas().stream().map(LogReplica::file).collect(Collectors.toList());
}
@VisibleForTesting
List getFilePaths()
{
return replicas().stream().map(LogReplica::file).map(File::getPath).collect(Collectors.toList());
}
}