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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.locator;
import java.util.*;
import java.util.Map.Entry;
import org.apache.cassandra.locator.ReplicaCollection.Builder.Conflict;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.dht.Datacenters;
import org.apache.cassandra.dht.Range;
import org.apache.cassandra.exceptions.ConfigurationException;
import org.apache.cassandra.dht.Token;
import org.apache.cassandra.locator.TokenMetadata.Topology;
import org.apache.cassandra.schema.SchemaConstants;
import org.apache.cassandra.service.ClientWarn;
import org.apache.cassandra.service.StorageService;
import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.Pair;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.Multimap;
import com.google.common.collect.Multimaps;
/**
*
* This Replication Strategy takes a property file that gives the intended
* replication factor in each datacenter. The sum total of the datacenter
* replication factor values should be equal to the keyspace replication
* factor.
*
*
* So for example, if the keyspace replication factor is 6, the
* datacenter replication factors could be 3, 2, and 1 - so 3 replicas in
* one datacenter, 2 in another, and 1 in another - totaling 6.
*
* This class also caches the Endpoints and invalidates the cache if there is a
* change in the number of tokens.
*/
public class NetworkTopologyStrategy extends AbstractReplicationStrategy
{
public static final String REPLICATION_FACTOR = "replication_factor";
private final Map datacenters;
private final ReplicationFactor aggregateRf;
private static final Logger logger = LoggerFactory.getLogger(NetworkTopologyStrategy.class);
public NetworkTopologyStrategy(String keyspaceName, TokenMetadata tokenMetadata, IEndpointSnitch snitch, Map configOptions) throws ConfigurationException
{
super(keyspaceName, tokenMetadata, snitch, configOptions);
int replicas = 0;
int trans = 0;
Map newDatacenters = new HashMap<>();
if (configOptions != null)
{
for (Entry entry : configOptions.entrySet())
{
String dc = entry.getKey();
// prepareOptions should have transformed any "replication_factor" options by now
if (dc.equalsIgnoreCase(REPLICATION_FACTOR))
throw new ConfigurationException(REPLICATION_FACTOR + " should not appear as an option at construction time for NetworkTopologyStrategy");
ReplicationFactor rf = ReplicationFactor.fromString(entry.getValue());
replicas += rf.allReplicas;
trans += rf.transientReplicas();
newDatacenters.put(dc, rf);
}
}
datacenters = Collections.unmodifiableMap(newDatacenters);
aggregateRf = ReplicationFactor.withTransient(replicas, trans);
}
/**
* Endpoint adder applying the replication rules for a given DC.
*/
private static final class DatacenterEndpoints
{
/** List accepted endpoints get pushed into. */
EndpointsForRange.Builder replicas;
/**
* Racks encountered so far. Replicas are put into separate racks while possible.
* For efficiency the set is shared between the instances, using the location pair (dc, rack) to make sure
* clashing names aren't a problem.
*/
Set> racks;
/** Number of replicas left to fill from this DC. */
int rfLeft;
int acceptableRackRepeats;
int transients;
DatacenterEndpoints(ReplicationFactor rf,
int rackCount,
int nodeCount,
EndpointsForRange.Builder replicas,
Set> racks)
{
this.replicas = replicas;
this.racks = racks;
// If there aren't enough nodes in this DC to fill the RF, the number of nodes is the effective RF.
this.rfLeft = Math.min(rf.allReplicas, nodeCount);
// If there aren't enough racks in this DC to fill the RF, we'll still use at least one node from each rack,
// and the difference is to be filled by the first encountered nodes.
acceptableRackRepeats = rf.allReplicas - rackCount;
// if we have fewer replicas than rf calls for, reduce transients accordingly
int reduceTransients = rf.allReplicas - this.rfLeft;
transients = Math.max(rf.transientReplicas() - reduceTransients, 0);
ReplicationFactor.validate(rfLeft, transients);
}
/**
* Attempts to add an endpoint to the replicas for this datacenter, adding to the replicas set if successful.
* Returns true if the endpoint was added, and this datacenter does not require further replicas.
*/
boolean addEndpointAndCheckIfDone(InetAddressAndPort ep, Pair location, Range replicatedRange)
{
if (done())
return false;
if (replicas.endpoints().contains(ep))
// Cannot repeat a node.
return false;
Replica replica = new Replica(ep, replicatedRange, rfLeft > transients);
if (racks.add(location))
{
// New rack.
--rfLeft;
replicas.add(replica, Conflict.NONE);
return done();
}
if (acceptableRackRepeats <= 0)
// There must be rfLeft distinct racks left, do not add any more rack repeats.
return false;
replicas.add(replica, Conflict.NONE);
// Added a node that is from an already met rack to match RF when there aren't enough racks.
--acceptableRackRepeats;
--rfLeft;
return done();
}
boolean done()
{
assert rfLeft >= 0;
return rfLeft == 0;
}
}
/**
* calculate endpoints in one pass through the tokens by tracking our progress in each DC.
*/
@Override
public EndpointsForRange calculateNaturalReplicas(Token searchToken, TokenMetadata tokenMetadata)
{
// we want to preserve insertion order so that the first added endpoint becomes primary
ArrayList sortedTokens = tokenMetadata.sortedTokens();
Token replicaEnd = TokenMetadata.firstToken(sortedTokens, searchToken);
Token replicaStart = tokenMetadata.getPredecessor(replicaEnd);
Range replicatedRange = new Range<>(replicaStart, replicaEnd);
EndpointsForRange.Builder builder = new EndpointsForRange.Builder(replicatedRange);
Set> seenRacks = new HashSet<>();
Topology topology = tokenMetadata.getTopology();
// all endpoints in each DC, so we can check when we have exhausted all the members of a DC
Multimap allEndpoints = topology.getDatacenterEndpoints();
// all racks in a DC so we can check when we have exhausted all racks in a DC
Map> racks = topology.getDatacenterRacks();
assert !allEndpoints.isEmpty() && !racks.isEmpty() : "not aware of any cluster members";
int dcsToFill = 0;
Map dcs = new HashMap<>(datacenters.size() * 2);
// Create a DatacenterEndpoints object for each non-empty DC.
for (Map.Entry en : datacenters.entrySet())
{
String dc = en.getKey();
ReplicationFactor rf = en.getValue();
int nodeCount = sizeOrZero(allEndpoints.get(dc));
if (rf.allReplicas <= 0 || nodeCount <= 0)
continue;
DatacenterEndpoints dcEndpoints = new DatacenterEndpoints(rf, sizeOrZero(racks.get(dc)), nodeCount, builder, seenRacks);
dcs.put(dc, dcEndpoints);
++dcsToFill;
}
Iterator tokenIter = TokenMetadata.ringIterator(sortedTokens, searchToken, false);
while (dcsToFill > 0 && tokenIter.hasNext())
{
Token next = tokenIter.next();
InetAddressAndPort ep = tokenMetadata.getEndpoint(next);
Pair location = topology.getLocation(ep);
DatacenterEndpoints dcEndpoints = dcs.get(location.left);
if (dcEndpoints != null && dcEndpoints.addEndpointAndCheckIfDone(ep, location, replicatedRange))
--dcsToFill;
}
return builder.build();
}
private int sizeOrZero(Multimap collection)
{
return collection != null ? collection.asMap().size() : 0;
}
private int sizeOrZero(Collection collection)
{
return collection != null ? collection.size() : 0;
}
@Override
public ReplicationFactor getReplicationFactor()
{
return aggregateRf;
}
public ReplicationFactor getReplicationFactor(String dc)
{
ReplicationFactor replicas = datacenters.get(dc);
return replicas == null ? ReplicationFactor.ZERO : replicas;
}
public Set getDatacenters()
{
return datacenters.keySet();
}
@Override
public Collection recognizedOptions()
{
// only valid options are valid DC names.
return Datacenters.getValidDatacenters();
}
/**
* Support datacenter auto-expansion for CASSANDRA-14303. This hook allows us to safely auto-expand
* the "replication_factor" options out into the known datacenters. It is called via reflection from
* {@link AbstractReplicationStrategy#prepareReplicationStrategyOptions(Class, Map, Map)}.
*
* @param options The proposed strategy options that will be potentially mutated
* @param previousOptions Any previous strategy options in the case of an ALTER statement
*/
protected static void prepareOptions(Map options, Map previousOptions)
{
String replication = options.remove(REPLICATION_FACTOR);
if (replication == null && options.size() == 0)
{
// Support direct alters from SimpleStrategy to NTS
replication = previousOptions.get(REPLICATION_FACTOR);
}
else if (replication != null)
{
// When datacenter auto-expansion occurs in e.g. an ALTER statement (meaning that the previousOptions
// map is not empty) we choose not to alter existing datacenter replication levels for safety.
previousOptions.entrySet().stream()
.filter(e -> !e.getKey().equals(REPLICATION_FACTOR)) // SimpleStrategy conversions
.forEach(e -> options.putIfAbsent(e.getKey(), e.getValue()));
}
if (replication != null) {
ReplicationFactor defaultReplicas = ReplicationFactor.fromString(replication);
Datacenters.getValidDatacenters()
.forEach(dc -> options.putIfAbsent(dc, defaultReplicas.toParseableString()));
}
options.values().removeAll(Collections.singleton("0"));
}
@Override
protected void validateExpectedOptions() throws ConfigurationException
{
// Do not accept query with no data centers specified.
if (this.configOptions.isEmpty())
{
throw new ConfigurationException("Configuration for at least one datacenter must be present");
}
// Validate the data center names
super.validateExpectedOptions();
logger.info("Configured datacenter replicas are {}", FBUtilities.toString(datacenters));
}
@Override
public void validateOptions() throws ConfigurationException
{
for (Entry e : this.configOptions.entrySet())
{
// prepareOptions should have transformed any "replication_factor" by now
if (e.getKey().equalsIgnoreCase(REPLICATION_FACTOR))
throw new ConfigurationException(REPLICATION_FACTOR + " should not appear as an option to NetworkTopologyStrategy");
validateReplicationFactor(e.getValue());
}
}
@Override
public void maybeWarnOnOptions()
{
if (!SchemaConstants.isSystemKeyspace(keyspaceName))
{
ImmutableMultimap dcsNodes = Multimaps.index(StorageService.instance.getTokenMetadata().getAllMembers(), snitch::getDatacenter);
for (Entry e : this.configOptions.entrySet())
{
String dc = e.getKey();
ReplicationFactor rf = getReplicationFactor(dc);
int nodeCount = dcsNodes.get(dc).size();
// nodeCount==0 on many tests
if (rf.fullReplicas > nodeCount && nodeCount != 0)
{
String msg = "Your replication factor " + rf.fullReplicas
+ " for keyspace "
+ keyspaceName
+ " is higher than the number of nodes "
+ nodeCount
+ " for datacenter "
+ dc;
ClientWarn.instance.warn(msg);
logger.warn(msg);
}
}
}
}
@Override
public boolean hasSameSettings(AbstractReplicationStrategy other)
{
return super.hasSameSettings(other) && ((NetworkTopologyStrategy) other).datacenters.equals(datacenters);
}
}
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