org.apache.hadoop.hdfs.server.blockmanagement

Class BlockPlacementPolicyWithNodeGroup

java.lang.Object

org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy

org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault

org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyWithNodeGroup

public class BlockPlacementPolicyWithNodeGroup
extends org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault

The class is responsible for choosing the desired number of targets for placing block replicas on environment with node-group layer. The replica placement strategy is adjusted to: If the writer is on a datanode, the 1st replica is placed on the local node (or local node-group), otherwise a random datanode. The 2nd replica is placed on a datanode that is on a different rack with 1st replica node. The 3rd replica is placed on a datanode which is on a different node-group but the same rack as the second replica node.

Field Summary

Fields inherited from class org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault

clusterMap, considerLoad, heartbeatInterval, host2datanodeMap, tolerateHeartbeatMultiplier

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	BlockPlacementPolicyWithNodeGroup()
protected	BlockPlacementPolicyWithNodeGroup(Configuration conf, org.apache.hadoop.hdfs.server.blockmanagement.FSClusterStats stats, NetworkTopology clusterMap, org.apache.hadoop.hdfs.server.blockmanagement.DatanodeManager datanodeManager)

Method Summary

Modifier and Type	Method and Description
protected int	addToExcludedNodes(org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor chosenNode, Set<Node> excludedNodes) Find other nodes in the same nodegroup of localMachine and add them into excludeNodes as replica should not be duplicated for nodes within the same nodegroup
protected DatanodeStorageInfo	chooseLocalRack(Node localMachine, Set<Node> excludedNodes, long blocksize, int maxNodesPerRack, List<DatanodeStorageInfo> results, boolean avoidStaleNodes, EnumMap<StorageType,Integer> storageTypes) Choose one node from the rack that localMachine is on.
protected DatanodeStorageInfo	chooseLocalStorage(Node localMachine, Set<Node> excludedNodes, long blocksize, int maxNodesPerRack, List<DatanodeStorageInfo> results, boolean avoidStaleNodes, EnumMap<StorageType,Integer> storageTypes, boolean fallbackToLocalRack) choose local node of localMachine as the target.
protected void	chooseRemoteRack(int numOfReplicas, org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor localMachine, Set<Node> excludedNodes, long blocksize, int maxReplicasPerRack, List<DatanodeStorageInfo> results, boolean avoidStaleNodes, EnumMap<StorageType,Integer> storageTypes) Choose numOfReplicas nodes from the racks that localMachine is NOT on.
protected String	getRack(org.apache.hadoop.hdfs.protocol.DatanodeInfo cur) Get rack string from a data node
void	initialize(Configuration conf, org.apache.hadoop.hdfs.server.blockmanagement.FSClusterStats stats, NetworkTopology clusterMap, org.apache.hadoop.hdfs.server.blockmanagement.Host2NodesMap host2datanodeMap) Used to setup a BlockPlacementPolicy object.
Collection<DatanodeStorageInfo>	pickupReplicaSet(Collection<DatanodeStorageInfo> first, Collection<DatanodeStorageInfo> second, Map<String,List<DatanodeStorageInfo>> rackMap) Pick up replica node set for deleting replica as over-replicated.

Methods inherited from class org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault

chooseDataNode, chooseRandom, chooseRandom, chooseReplicasToDelete, chooseReplicaToDelete, chooseTarget, verifyBlockPlacement

Methods inherited from class org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy

adjustSetsWithChosenReplica, getInstance, splitNodesWithRack

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BlockPlacementPolicyWithNodeGroup

protected BlockPlacementPolicyWithNodeGroup(Configuration conf,
                                            org.apache.hadoop.hdfs.server.blockmanagement.FSClusterStats stats,
                                            NetworkTopology clusterMap,
                                            org.apache.hadoop.hdfs.server.blockmanagement.DatanodeManager datanodeManager)

BlockPlacementPolicyWithNodeGroup

protected BlockPlacementPolicyWithNodeGroup()

Method Detail

initialize

public void initialize(Configuration conf,
                       org.apache.hadoop.hdfs.server.blockmanagement.FSClusterStats stats,
                       NetworkTopology clusterMap,
                       org.apache.hadoop.hdfs.server.blockmanagement.Host2NodesMap host2datanodeMap)

Description copied from class: org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy

Used to setup a BlockPlacementPolicy object. This should be defined by all implementations of a BlockPlacementPolicy.

Overrides:

initialize in class org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault

Parameters:

conf - the configuration object

stats - retrieve cluster status from here

clusterMap - cluster topology

chooseLocalStorage

protected DatanodeStorageInfo chooseLocalStorage(Node localMachine,
                                                 Set<Node> excludedNodes,
                                                 long blocksize,
                                                 int maxNodesPerRack,
                                                 List<DatanodeStorageInfo> results,
                                                 boolean avoidStaleNodes,
                                                 EnumMap<StorageType,Integer> storageTypes,
                                                 boolean fallbackToLocalRack)
                                          throws org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy.NotEnoughReplicasException

choose local node of localMachine as the target. if localMachine is not available, choose a node on the same nodegroup or rack instead.

Overrides:

chooseLocalStorage in class org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault

Returns:

the chosen node

Throws:

org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy.NotEnoughReplicasException

chooseLocalRack

protected DatanodeStorageInfo chooseLocalRack(Node localMachine,
                                              Set<Node> excludedNodes,
                                              long blocksize,
                                              int maxNodesPerRack,
                                              List<DatanodeStorageInfo> results,
                                              boolean avoidStaleNodes,
                                              EnumMap<StorageType,Integer> storageTypes)
                                       throws org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy.NotEnoughReplicasException

Description copied from class: org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault

Choose one node from the rack that localMachine is on. if no such node is available, choose one node from the rack where a second replica is on. if still no such node is available, choose a random node in the cluster.

Overrides:

chooseLocalRack in class org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault

Returns:

the chosen node

Throws:

org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy.NotEnoughReplicasException

chooseRemoteRack

protected void chooseRemoteRack(int numOfReplicas,
                                org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor localMachine,
                                Set<Node> excludedNodes,
                                long blocksize,
                                int maxReplicasPerRack,
                                List<DatanodeStorageInfo> results,
                                boolean avoidStaleNodes,
                                EnumMap<StorageType,Integer> storageTypes)
                         throws org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy.NotEnoughReplicasException

Choose numOfReplicas nodes from the racks that localMachine is NOT on. if not enough nodes are available, choose the remaining ones from the local rack

Overrides:

chooseRemoteRack in class org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault

Throws:

org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy.NotEnoughReplicasException

getRack

protected String getRack(org.apache.hadoop.hdfs.protocol.DatanodeInfo cur)

Description copied from class: org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy

Get rack string from a data node

Overrides:

getRack in class org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicy

Returns:

rack of data node

addToExcludedNodes

protected int addToExcludedNodes(org.apache.hadoop.hdfs.server.blockmanagement.DatanodeDescriptor chosenNode,
                                 Set<Node> excludedNodes)

Find other nodes in the same nodegroup of localMachine and add them into excludeNodes as replica should not be duplicated for nodes within the same nodegroup

Overrides:

addToExcludedNodes in class org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault

Returns:

number of new excluded nodes

pickupReplicaSet

public Collection<DatanodeStorageInfo> pickupReplicaSet(Collection<DatanodeStorageInfo> first,
                                                        Collection<DatanodeStorageInfo> second,
                                                        Map<String,List<DatanodeStorageInfo>> rackMap)

Pick up replica node set for deleting replica as over-replicated. First set contains replica nodes on rack with more than one replica while second set contains remaining replica nodes. If first is not empty, divide first set into two subsets: moreThanOne contains nodes on nodegroup with more than one replica exactlyOne contains the remaining nodes in first set then pickup priSet if not empty. If first is empty, then pick second.

Overrides:

pickupReplicaSet in class org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault