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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;
import com.carrotsearch.hppc.ObjectIntHashMap;
import org.apache.cassandra.locator.Endpoints;
import org.apache.cassandra.schema.TableMetadata;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.exceptions.InvalidRequestException;
import org.apache.cassandra.locator.AbstractReplicationStrategy;
import org.apache.cassandra.locator.NetworkTopologyStrategy;
import org.apache.cassandra.transport.ProtocolException;
import static org.apache.cassandra.locator.Replicas.addToCountPerDc;
import static org.apache.cassandra.locator.Replicas.countInOurDc;
public enum ConsistencyLevel
{
ANY (0),
ONE (1),
TWO (2),
THREE (3),
QUORUM (4),
ALL (5),
LOCAL_QUORUM(6, true),
EACH_QUORUM (7),
SERIAL (8),
LOCAL_SERIAL(9),
LOCAL_ONE (10, true),
NODE_LOCAL (11, true);
// Used by the binary protocol
public final int code;
private final boolean isDCLocal;
private static final ConsistencyLevel[] codeIdx;
static
{
int maxCode = -1;
for (ConsistencyLevel cl : ConsistencyLevel.values())
maxCode = Math.max(maxCode, cl.code);
codeIdx = new ConsistencyLevel[maxCode + 1];
for (ConsistencyLevel cl : ConsistencyLevel.values())
{
if (codeIdx[cl.code] != null)
throw new IllegalStateException("Duplicate code");
codeIdx[cl.code] = cl;
}
}
private ConsistencyLevel(int code)
{
this(code, false);
}
private ConsistencyLevel(int code, boolean isDCLocal)
{
this.code = code;
this.isDCLocal = isDCLocal;
}
public static ConsistencyLevel fromCode(int code)
{
if (code < 0 || code >= codeIdx.length)
throw new ProtocolException(String.format("Unknown code %d for a consistency level", code));
return codeIdx[code];
}
public static int quorumFor(AbstractReplicationStrategy replicationStrategy)
{
return (replicationStrategy.getReplicationFactor().allReplicas / 2) + 1;
}
public static int localQuorumFor(AbstractReplicationStrategy replicationStrategy, String dc)
{
return (replicationStrategy instanceof NetworkTopologyStrategy)
? (((NetworkTopologyStrategy) replicationStrategy).getReplicationFactor(dc).allReplicas / 2) + 1
: quorumFor(replicationStrategy);
}
public static int localQuorumForOurDc(AbstractReplicationStrategy replicationStrategy)
{
return localQuorumFor(replicationStrategy, DatabaseDescriptor.getLocalDataCenter());
}
public static ObjectIntHashMap eachQuorumForRead(AbstractReplicationStrategy replicationStrategy)
{
if (replicationStrategy instanceof NetworkTopologyStrategy)
{
NetworkTopologyStrategy npStrategy = (NetworkTopologyStrategy) replicationStrategy;
ObjectIntHashMap perDc = new ObjectIntHashMap<>(((npStrategy.getDatacenters().size() + 1) * 4) / 3);
for (String dc : npStrategy.getDatacenters())
perDc.put(dc, ConsistencyLevel.localQuorumFor(replicationStrategy, dc));
return perDc;
}
else
{
ObjectIntHashMap perDc = new ObjectIntHashMap<>(1);
perDc.put(DatabaseDescriptor.getLocalDataCenter(), quorumFor(replicationStrategy));
return perDc;
}
}
public static ObjectIntHashMap eachQuorumForWrite(AbstractReplicationStrategy replicationStrategy, Endpoints pendingWithDown)
{
ObjectIntHashMap perDc = eachQuorumForRead(replicationStrategy);
addToCountPerDc(perDc, pendingWithDown, 1);
return perDc;
}
public int blockFor(AbstractReplicationStrategy replicationStrategy)
{
switch (this)
{
case ONE:
case LOCAL_ONE:
return 1;
case ANY:
return 1;
case TWO:
return 2;
case THREE:
return 3;
case QUORUM:
case SERIAL:
return quorumFor(replicationStrategy);
case ALL:
return replicationStrategy.getReplicationFactor().allReplicas;
case LOCAL_QUORUM:
case LOCAL_SERIAL:
return localQuorumForOurDc(replicationStrategy);
case EACH_QUORUM:
if (replicationStrategy instanceof NetworkTopologyStrategy)
{
NetworkTopologyStrategy strategy = (NetworkTopologyStrategy) replicationStrategy;
int n = 0;
for (String dc : strategy.getDatacenters())
n += localQuorumFor(replicationStrategy, dc);
return n;
}
else
{
return quorumFor(replicationStrategy);
}
default:
throw new UnsupportedOperationException("Invalid consistency level: " + toString());
}
}
public int blockForWrite(AbstractReplicationStrategy replicationStrategy, Endpoints pending)
{
assert pending != null;
int blockFor = blockFor(replicationStrategy);
switch (this)
{
case ANY:
break;
case LOCAL_ONE: case LOCAL_QUORUM: case LOCAL_SERIAL:
// we will only count local replicas towards our response count, as these queries only care about local guarantees
blockFor += countInOurDc(pending).allReplicas();
break;
case ONE: case TWO: case THREE:
case QUORUM: case EACH_QUORUM:
case SERIAL:
case ALL:
blockFor += pending.size();
}
return blockFor;
}
/**
* Determine if this consistency level meets or exceeds the consistency requirements of the given cl for the given keyspace
* WARNING: this is not locality aware; you cannot safely use this with mixed locality consistency levels (e.g. LOCAL_QUORUM and QUORUM)
*/
public boolean satisfies(ConsistencyLevel other, AbstractReplicationStrategy replicationStrategy)
{
return blockFor(replicationStrategy) >= other.blockFor(replicationStrategy);
}
public boolean isDatacenterLocal()
{
return isDCLocal;
}
public void validateForRead() throws InvalidRequestException
{
switch (this)
{
case ANY:
throw new InvalidRequestException("ANY ConsistencyLevel is only supported for writes");
}
}
public void validateForWrite() throws InvalidRequestException
{
switch (this)
{
case SERIAL:
case LOCAL_SERIAL:
throw new InvalidRequestException("You must use conditional updates for serializable writes");
}
}
// This is the same than validateForWrite really, but we include a slightly different error message for SERIAL/LOCAL_SERIAL
public void validateForCasCommit(AbstractReplicationStrategy replicationStrategy) throws InvalidRequestException
{
switch (this)
{
case EACH_QUORUM:
requireNetworkTopologyStrategy(replicationStrategy);
break;
case SERIAL:
case LOCAL_SERIAL:
throw new InvalidRequestException(this + " is not supported as conditional update commit consistency. Use ANY if you mean \"make sure it is accepted but I don't care how many replicas commit it for non-SERIAL reads\"");
}
}
public void validateForCas() throws InvalidRequestException
{
if (!isSerialConsistency())
throw new InvalidRequestException("Invalid consistency for conditional update. Must be one of SERIAL or LOCAL_SERIAL");
}
public boolean isSerialConsistency()
{
return this == SERIAL || this == LOCAL_SERIAL;
}
public void validateCounterForWrite(TableMetadata metadata) throws InvalidRequestException
{
if (this == ConsistencyLevel.ANY)
throw new InvalidRequestException("Consistency level ANY is not yet supported for counter table " + metadata.name);
if (isSerialConsistency())
throw new InvalidRequestException("Counter operations are inherently non-serializable");
}
private void requireNetworkTopologyStrategy(AbstractReplicationStrategy replicationStrategy) throws InvalidRequestException
{
if (!(replicationStrategy instanceof NetworkTopologyStrategy))
throw new InvalidRequestException(String.format("consistency level %s not compatible with replication strategy (%s)",
this, replicationStrategy.getClass().getName()));
}
}