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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.net.InetAddress;
import java.util.*;
import java.util.Map.Entry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.cassandra.exceptions.ConfigurationException;
import org.apache.cassandra.dht.Token;
import org.apache.cassandra.locator.TokenMetadata.Topology;
import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.Pair;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.Multimap;
/**
*
* 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 - totalling 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
{
private final Map datacenters;
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);
Map newDatacenters = new HashMap();
if (configOptions != null)
{
for (Entry entry : configOptions.entrySet())
{
String dc = entry.getKey();
if (dc.equalsIgnoreCase("replication_factor"))
throw new ConfigurationException("replication_factor is an option for SimpleStrategy, not NetworkTopologyStrategy");
Integer replicas = Integer.valueOf(entry.getValue());
newDatacenters.put(dc, replicas);
}
}
datacenters = Collections.unmodifiableMap(newDatacenters);
logger.trace("Configured datacenter replicas are {}", FBUtilities.toString(datacenters));
}
/**
* Endpoint adder applying the replication rules for a given DC.
*/
private static final class DatacenterEndpoints
{
/** List accepted endpoints get pushed into. */
Set endpoints;
/**
* 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;
DatacenterEndpoints(int rf, int rackCount, int nodeCount, Set endpoints, Set> racks)
{
this.endpoints = endpoints;
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, 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 - rackCount;
}
/**
* Attempts to add an endpoint to the replicas for this datacenter, adding to the endpoints set if successful.
* Returns true if the endpoint was added, and this datacenter does not require further replicas.
*/
boolean addEndpointAndCheckIfDone(InetAddress ep, Pair location)
{
if (done())
return false;
if (racks.add(location))
{
// New rack.
--rfLeft;
boolean added = endpoints.add(ep);
assert added;
return done();
}
if (acceptableRackRepeats <= 0)
// There must be rfLeft distinct racks left, do not add any more rack repeats.
return false;
if (!endpoints.add(ep))
// Cannot repeat a node.
return false;
// 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.
*/
public List calculateNaturalEndpoints(Token searchToken, TokenMetadata tokenMetadata)
{
// we want to preserve insertion order so that the first added endpoint becomes primary
Set replicas = new LinkedHashSet<>();
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();
int rf = en.getValue();
int nodeCount = sizeOrZero(allEndpoints.get(dc));
if (rf <= 0 || nodeCount <= 0)
continue;
DatacenterEndpoints dcEndpoints = new DatacenterEndpoints(rf, sizeOrZero(racks.get(dc)), nodeCount, replicas, seenRacks);
dcs.put(dc, dcEndpoints);
++dcsToFill;
}
Iterator tokenIter = TokenMetadata.ringIterator(tokenMetadata.sortedTokens(), searchToken, false);
while (dcsToFill > 0 && tokenIter.hasNext())
{
Token next = tokenIter.next();
InetAddress ep = tokenMetadata.getEndpoint(next);
Pair location = topology.getLocation(ep);
DatacenterEndpoints dcEndpoints = dcs.get(location.left);
if (dcEndpoints != null && dcEndpoints.addEndpointAndCheckIfDone(ep, location))
--dcsToFill;
}
return new ArrayList<>(replicas);
}
private int sizeOrZero(Multimap collection)
{
return collection != null ? collection.asMap().size() : 0;
}
private int sizeOrZero(Collection collection)
{
return collection != null ? collection.size() : 0;
}
public int getReplicationFactor()
{
int total = 0;
for (int repFactor : datacenters.values())
total += repFactor;
return total;
}
public int getReplicationFactor(String dc)
{
Integer replicas = datacenters.get(dc);
return replicas == null ? 0 : replicas;
}
public Set getDatacenters()
{
return datacenters.keySet();
}
public void validateOptions() throws ConfigurationException
{
for (Entry e : this.configOptions.entrySet())
{
if (e.getKey().equalsIgnoreCase("replication_factor"))
throw new ConfigurationException("replication_factor is an option for SimpleStrategy, not NetworkTopologyStrategy");
validateReplicationFactor(e.getValue());
}
}
@Override
public boolean hasSameSettings(AbstractReplicationStrategy other)
{
return super.hasSameSettings(other) && ((NetworkTopologyStrategy) other).datacenters.equals(datacenters);
}
}