/*
* 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;
import java.nio.ByteBuffer;
import org.apache.cassandra.db.ColumnFamily;
import org.apache.cassandra.db.ReadResponse;
import org.apache.cassandra.db.Row;
import org.apache.cassandra.net.MessageIn;
public class RowDigestResolver extends AbstractRowResolver
{
public RowDigestResolver(String table, ByteBuffer key)
{
super(key, table);
}
/**
* Special case of resolve() so that CL.ONE reads never throw DigestMismatchException in the foreground
*/
public Row getData()
{
for (MessageIn<ReadResponse> message : replies)
{
ReadResponse result = message.payload;
if (!result.isDigestQuery())
return result.row();
}
throw new AssertionError("getData should not be invoked when no data is present");
}
/*
* This method handles two different scenarios:
*
* a) we're handling the initial read, of data from the closest replica + digests
* from the rest. In this case we check the digests against each other,
* throw an exception if there is a mismatch, otherwise return the data row.
*
* b) we're checking additional digests that arrived after the minimum to handle
* the requested ConsistencyLevel, i.e. asynchronous read repair check
*/
public Row resolve() throws DigestMismatchException
{
if (logger.isDebugEnabled())
logger.debug("resolving " + replies.size() + " responses");
long startTime = System.currentTimeMillis();
// validate digests against each other; throw immediately on mismatch.
// also extract the data reply, if any.
ColumnFamily data = null;
ByteBuffer digest = null;
for (MessageIn<ReadResponse> message : replies)
{
ReadResponse response = message.payload;
if (response.isDigestQuery())
{
if (digest == null)
{
digest = response.digest();
}
else
{
ByteBuffer digest2 = response.digest();
if (!digest.equals(digest2))
throw new DigestMismatchException(key, digest, digest2);
}
}
else
{
data = response.row().cf;
}
}
// Compare digest (only one, since we threw earlier if there were different replies)
// with the data response. If there is a mismatch then throw an exception so that read repair can happen.
//
// It's important to note that we do not consider the possibility of multiple data responses --
// that can only happen when we're doing the repair post-mismatch, and will be handled by RowDataResolver.
if (digest != null)
{
ByteBuffer digest2 = ColumnFamily.digest(data);
if (!digest.equals(digest2))
throw new DigestMismatchException(key, digest, digest2);
if (logger.isDebugEnabled())
logger.debug("digests verified");
}
if (logger.isDebugEnabled())
logger.debug("resolve: " + (System.currentTimeMillis() - startTime) + " ms.");
return new Row(key, data);
}
public boolean isDataPresent()
{
for (MessageIn<ReadResponse> message : replies)
{
if (!message.payload.isDigestQuery())
return true;
}
return false;
}
}