How to use

Host2NodesMap

in

org.apache.hadoop.hdfs.server.blockmanagement

/** Add a datanode. */
void addDatanode(final DatanodeDescriptor node) {
 // To keep host2DatanodeMap consistent with datanodeMap,
 // remove  from host2DatanodeMap the datanodeDescriptor removed
 // from datanodeMap before adding node to host2DatanodeMap.
 synchronized(this) {
  host2DatanodeMap.remove(datanodeMap.put(node.getDatanodeUuid(), node));
 }
 networktopology.add(node); // may throw InvalidTopologyException
 host2DatanodeMap.add(node);
 checkIfClusterIsNowMultiRack(node);
 resolveUpgradeDomain(node);
 if (LOG.isDebugEnabled()) {
  LOG.debug(getClass().getSimpleName() + ".addDatanode: "
    + "node " + node + " is added to datanodeMap.");
 }
}

hostmapLock.writeLock().lock();
try {
 if (node==null || contains(node)) {
  return false;

/** @return the datanode descriptor for the host. */
public DatanodeDescriptor getDatanodeByHost(final String host) {
 return host2DatanodeMap.getDatanodeByHost(host);
}

@Test
public void testRemove() throws Exception {
 DatanodeDescriptor nodeNotInMap =
  DFSTestUtil.getDatanodeDescriptor("3.3.3.3", "/d1/r4");
 assertFalse(map.remove(nodeNotInMap));
 
 assertTrue(map.remove(dataNodes[0]));
 assertTrue(map.getDatanodeByHost("1.1.1.1.")==null);
 assertTrue(map.getDatanodeByHost("2.2.2.2")==dataNodes[1]);
 DatanodeDescriptor node = map.getDatanodeByHost("3.3.3.3");
 assertTrue(node==dataNodes[2] || node==dataNodes[3]);
 assertNull(map.getDatanodeByHost("4.4.4.4"));
 
 assertTrue(map.remove(dataNodes[2]));
 assertNull(map.getDatanodeByHost("1.1.1.1"));
 assertEquals(map.getDatanodeByHost("2.2.2.2"), dataNodes[1]);
 assertEquals(map.getDatanodeByHost("3.3.3.3"), dataNodes[3]);
 
 assertTrue(map.remove(dataNodes[3]));
 assertNull(map.getDatanodeByHost("1.1.1.1"));
 assertEquals(map.getDatanodeByHost("2.2.2.2"), dataNodes[1]);
 assertNull(map.getDatanodeByHost("3.3.3.3"));
 
 assertFalse(map.remove(null));
 assertTrue(map.remove(dataNodes[1]));
 assertFalse(map.remove(dataNodes[1]));
}

/** @return the datanode descriptor for the host. */
public DatanodeDescriptor getDatanodeByXferAddr(String host, int xferPort) {
 return host2DatanodeMap.getDatanodeByXferAddr(host, xferPort);
}

/** Physically remove node from datanodeMap. */
private void wipeDatanode(final DatanodeID node) {
 final String key = node.getDatanodeUuid();
 synchronized (this) {
  host2DatanodeMap.remove(datanodeMap.remove(key));
 }
 if (LOG.isDebugEnabled()) {
  LOG.debug(getClass().getSimpleName() + ".wipeDatanode("
    + node + "): storage " + key 
    + " is removed from datanodeMap.");
 }
}

@Before
public void setup() {
 dataNodes = new DatanodeDescriptor[] {
   DFSTestUtil.getDatanodeDescriptor("1.1.1.1", "/d1/r1"),
   DFSTestUtil.getDatanodeDescriptor("2.2.2.2", "/d1/r1"),
   DFSTestUtil.getDatanodeDescriptor("3.3.3.3", "/d1/r2"),
   DFSTestUtil.getDatanodeDescriptor("3.3.3.3", 5021, "/d1/r2"),
 };
 for (DatanodeDescriptor node : dataNodes) {
  map.add(node);
 }
 map.add(null);
}

/**
 * Add all nodes from a dependent nodes list to excludedNodes.
 * @return number of new excluded nodes
 */
private int addDependentNodesToExcludedNodes(DatanodeDescriptor chosenNode,
  Set<Node> excludedNodes) {
 if (this.host2datanodeMap == null) {
  return 0;
 }
 int countOfExcludedNodes = 0;
 for(String hostname : chosenNode.getDependentHostNames()) {
  DatanodeDescriptor node =
    this.host2datanodeMap.getDataNodeByHostName(hostname);
  if(node!=null) {
   if (excludedNodes.add(node)) {
    countOfExcludedNodes++;
   }
  } else {
   LOG.warn("Not able to find datanode " + hostname
     + " which has dependency with datanode "
     + chosenNode.getHostName());
  }
 }
 
 return countOfExcludedNodes;
}

/** @return the datanode descriptor for the host. */
public DatanodeDescriptor getDatanodeByXferAddr(String host, int xferPort) {
 return host2DatanodeMap.getDatanodeByXferAddr(host, xferPort);
}

/** Physically remove node from datanodeMap. */
private void wipeDatanode(final DatanodeID node) {
 final String key = node.getDatanodeUuid();
 synchronized (datanodeMap) {
  host2DatanodeMap.remove(datanodeMap.remove(key));
 }
 // Also remove all block invalidation tasks under this node
 blockManager.removeFromInvalidates(new DatanodeInfo(node));
 if (LOG.isDebugEnabled()) {
  LOG.debug(getClass().getSimpleName() + ".wipeDatanode("
    + node + "): storage " + key 
    + " is removed from datanodeMap.");
 }
}

for(int i=0; i<NUM_OF_DATANODES_FOR_DEPENDENCIES; i++) {
 cluster.add(dataNodesForDependencies[i]);
 host2DatanodeMap.add(dataNodesForDependencies[i]);

/**
 * Add all nodes from a dependent nodes list to excludedNodes.
 * @return number of new excluded nodes
 */
private int addDependentNodesToExcludedNodes(DatanodeDescriptor chosenNode,
  Set<Node> excludedNodes) {
 if (this.host2datanodeMap == null) {
  return 0;
 }
 int countOfExcludedNodes = 0;
 for(String hostname : chosenNode.getDependentHostNames()) {
  DatanodeDescriptor node =
    this.host2datanodeMap.getDataNodeByHostName(hostname);
  if(node!=null) {
   if (excludedNodes.add(node)) {
    countOfExcludedNodes++;
   }
  } else {
   LOG.warn("Not able to find datanode " + hostname
     + " which has dependency with datanode "
     + chosenNode.getHostName());
  }
 }
 
 return countOfExcludedNodes;
}

/** Add a datanode. */
void addDatanode(final DatanodeDescriptor node) {
 // To keep host2DatanodeMap consistent with datanodeMap,
 // remove  from host2DatanodeMap the datanodeDescriptor removed
 // from datanodeMap before adding node to host2DatanodeMap.
 synchronized(datanodeMap) {
  host2DatanodeMap.remove(datanodeMap.put(node.getDatanodeUuid(), node));
 }
 networktopology.add(node); // may throw InvalidTopologyException
 host2DatanodeMap.add(node);
 checkIfClusterIsNowMultiRack(node);
 if (LOG.isDebugEnabled()) {
  LOG.debug(getClass().getSimpleName() + ".addDatanode: "
    + "node " + node + " is added to datanodeMap.");
 }
}

/** get a data node by its hostname. This should be used if only one 
 * datanode service is running on a hostname. If multiple datanodes
 * are running on a hostname then use methods getDataNodeByXferAddr and
 * getDataNodeByHostNameAndPort.
 * @return DatanodeDescriptor if found; otherwise null.
 */
DatanodeDescriptor getDataNodeByHostName(String hostname) {
 if(hostname == null) {
  return null;
 }
 
 hostmapLock.readLock().lock();
 try {
  String ipAddr = mapHost.get(hostname);
  if(ipAddr == null) {
   return null;
  } else {  
   return getDatanodeByHost(ipAddr);
  }
 } finally {
  hostmapLock.readLock().unlock();
 }
}

hostmapLock.writeLock().lock();
try {
 if (node==null || contains(node)) {
  return false;

/** @return the datanode descriptor for the host. */
public DatanodeDescriptor getDatanodeByXferAddr(String host, int xferPort) {
 return host2DatanodeMap.getDatanodeByXferAddr(host, xferPort);
}

/** Physically remove node from datanodeMap. */
private void wipeDatanode(final DatanodeID node) {
 final String key = node.getDatanodeUuid();
 synchronized (datanodeMap) {
  host2DatanodeMap.remove(datanodeMap.remove(key));
 }
 // Also remove all block invalidation tasks under this node
 blockManager.removeFromInvalidates(new DatanodeInfo(node));
 if (LOG.isDebugEnabled()) {
  LOG.debug(getClass().getSimpleName() + ".wipeDatanode("
    + node + "): storage " + key 
    + " is removed from datanodeMap.");
 }
}

/**
 * Add all nodes from a dependent nodes list to excludedNodes.
 * @return number of new excluded nodes
 */
private int addDependentNodesToExcludedNodes(DatanodeDescriptor chosenNode,
  Set<Node> excludedNodes) {
 if (this.host2datanodeMap == null) {
  return 0;
 }
 int countOfExcludedNodes = 0;
 for(String hostname : chosenNode.getDependentHostNames()) {
  DatanodeDescriptor node =
    this.host2datanodeMap.getDataNodeByHostName(hostname);
  if(node!=null) {
   if (excludedNodes.add(node)) {
    countOfExcludedNodes++;
   }
  } else {
   LOG.warn("Not able to find datanode " + hostname
     + " which has dependency with datanode "
     + chosenNode.getHostName());
  }
 }
 
 return countOfExcludedNodes;
}

/** Add a datanode. */
void addDatanode(final DatanodeDescriptor node) {
 // To keep host2DatanodeMap consistent with datanodeMap,
 // remove  from host2DatanodeMap the datanodeDescriptor removed
 // from datanodeMap before adding node to host2DatanodeMap.
 synchronized(datanodeMap) {
  host2DatanodeMap.remove(datanodeMap.put(node.getDatanodeUuid(), node));
 }
 networktopology.add(node); // may throw InvalidTopologyException
 host2DatanodeMap.add(node);
 checkIfClusterIsNowMultiRack(node);
 if (LOG.isDebugEnabled()) {
  LOG.debug(getClass().getSimpleName() + ".addDatanode: "
    + "node " + node + " is added to datanodeMap.");
 }
}

/** @return the datanode descriptor for the host. */
public DatanodeDescriptor getDatanodeByHost(final String host) {
 return host2DatanodeMap.getDatanodeByHost(host);
}