HADOOP-7772

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1189847 13f79535-47bb-0310-9956-ffa450edef68

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -1008,6 +1008,8 @@ Release 0.22.0 - Unreleased
     HADOOP-7325. The hadoop command should not accept class names starting with
     a hyphen. (Brock Noland via todd)
 
+    HADOOP-7772. javadoc the topology classes (stevel)
+
   OPTIMIZATIONS
 
     HADOOP-6884. Add LOG.isDebugEnabled() guard for each LOG.debug(..).

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/CachedDNSToSwitchMapping.java

@@ -37,14 +37,18 @@ import org.apache.hadoop.classification.InterfaceStability;
 public class CachedDNSToSwitchMapping implements DNSToSwitchMapping {
   private Map<String, String> cache = new ConcurrentHashMap<String, String>();
   protected DNSToSwitchMapping rawMapping;
-  
+
+  /**
+   * cache a raw DNS mapping
+   * @param rawMapping the raw mapping to cache
+   */
   public CachedDNSToSwitchMapping(DNSToSwitchMapping rawMapping) {
     this.rawMapping = rawMapping;
   }
-  
 
   /**
-   * Returns the hosts from 'names' that have not been cached previously
+   * @param names a list of hostnames to probe for being cached
+   * @return the hosts from 'names' that have not been cached previously
    */
   private List<String> getUncachedHosts(List<String> names) {
     // find out all names without cached resolved location
@@ -58,7 +62,12 @@ public class CachedDNSToSwitchMapping implements DNSToSwitchMapping {
   }
 
   /**
-   * Caches the resolved hosts
+   * Caches the resolved host:rack mappings. The two list
+   * parameters must be of equal size.
+   *
+   * @param uncachedHosts a list of hosts that were uncached
+   * @param resolvedHosts a list of resolved host entries where the element
+   * at index(i) is the resolved value for the entry in uncachedHosts[i]
    */
   private void cacheResolvedHosts(List<String> uncachedHosts, 
       List<String> resolvedHosts) {
@@ -71,8 +80,9 @@ public class CachedDNSToSwitchMapping implements DNSToSwitchMapping {
   }
 
   /**
-   * Returns the cached resolution of the list of hostnames/addresses.
-   * Returns null if any of the names are not currently in the cache
+   * @param names a list of hostnames to look up (can be be empty)
+   * @return the cached resolution of the list of hostnames/addresses.
+   *  or null if any of the names are not currently in the cache
    */
   private List<String> getCachedHosts(List<String> names) {
     List<String> result = new ArrayList<String>(names.size());
@@ -88,6 +98,7 @@ public class CachedDNSToSwitchMapping implements DNSToSwitchMapping {
     return result;
   }
 
+  @Override
   public List<String> resolve(List<String> names) {
     // normalize all input names to be in the form of IP addresses
     names = NetUtils.normalizeHostNames(names);
@@ -97,12 +108,14 @@ public class CachedDNSToSwitchMapping implements DNSToSwitchMapping {
       return result;
     }
 
-    List<String> uncachedHosts = this.getUncachedHosts(names);
+    List<String> uncachedHosts = getUncachedHosts(names);
 
     // Resolve the uncached hosts
     List<String> resolvedHosts = rawMapping.resolve(uncachedHosts);
-    this.cacheResolvedHosts(uncachedHosts, resolvedHosts);
-    return this.getCachedHosts(names);
+    //cache them
+    cacheResolvedHosts(uncachedHosts, resolvedHosts);
+    //now look up the entire list in the cache
+    return getCachedHosts(names);
 
   }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/DNSToSwitchMapping.java

@@ -23,7 +23,7 @@ import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
 
 /**
- * An interface that should be implemented to allow pluggable 
+ * An interface that must be implemented to allow pluggable
  * DNS-name/IP-address to RackID resolvers.
  *
  */
@@ -40,8 +40,9 @@ public interface DNSToSwitchMapping {
    * Note the hostname/ip-address is not part of the returned path.
    * The network topology of the cluster would determine the number of
    * components in the network path.
-   * @param names
-   * @return list of resolved network paths
+   * @param names the list of hosts to resolve (can be empty)
+   * @return list of resolved network paths.
+   * If <i>names</i> is empty, the returned list is also empty
    */
   public List<String> resolve(List<String> names);
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NetworkTopology.java

@@ -45,8 +45,8 @@ public class NetworkTopology {
   public static final Log LOG = 
     LogFactory.getLog(NetworkTopology.class);
     
-  /* Inner Node represent a switch/router of a data center or rack.
-   * Different from a leave node, it has non-null children.
+  /** InnerNode represents a switch/router of a data center or rack.
+   * Different from a leaf node, it has non-null children.
    */
   private class InnerNode extends NodeBase {
     private ArrayList<Node> children=new ArrayList<Node>();
@@ -68,16 +68,16 @@ public class NetworkTopology {
       super(name, location, parent, level);
     }
         
-    /** Get its children */
+    /** @return its children */
     Collection<Node> getChildren() {return children;}
         
-    /** Return the number of children this node has */
+    /** @return the number of children this node has */
     int getNumOfChildren() {
       return children.size();
     }
         
     /** Judge if this node represents a rack 
-     * Return true if it has no child or its children are not InnerNodes
+     * @return true if it has no child or its children are not InnerNodes
      */ 
     boolean isRack() {
       if (children.isEmpty()) {
@@ -225,7 +225,11 @@ public class NetworkTopology {
       }
     } // end of remove
         
-    /** Given a node's string representation, return a reference to the node */ 
+    /** Given a node's string representation, return a reference to the node
+     * @param loc string location of the form /rack/node
+     * @return null if the node is not found or the childnode is there but
+     * not an instance of {@link InnerNode}
+     */
     private Node getLoc(String loc) {
       if (loc == null || loc.length() == 0) return this;
             
@@ -246,7 +250,12 @@ public class NetworkTopology {
     }
         
     /** get <i>leafIndex</i> leaf of this subtree 
-     * if it is not in the <i>excludedNode</i>*/
+     * if it is not in the <i>excludedNode</i>
+     *
+     * @param leafIndex an indexed leaf of the node
+     * @param excludedNode an excluded node (can be null)
+     * @return
+     */
     private Node getLeaf(int leafIndex, Node excludedNode) {
       int count=0;
       // check if the excluded node a leaf
@@ -297,9 +306,14 @@ public class NetworkTopology {
       return numOfLeaves;
     }
   } // end of InnerNode
-    
-  InnerNode clusterMap = new InnerNode(InnerNode.ROOT); // the root
-  private int numOfRacks = 0;  // rack counter
+
+  /**
+   * the root cluster map
+   */
+  InnerNode clusterMap = new InnerNode(InnerNode.ROOT);
+  /** rack counter */
+  private int numOfRacks = 0;
+  /** the lock used to manage access */
   private ReadWriteLock netlock;
     
   public NetworkTopology() {
@@ -308,8 +322,7 @@ public class NetworkTopology {
     
   /** Add a leaf node
    * Update node counter & rack counter if necessary
-   * @param node
-   *          node to be added
+   * @param node node to be added; can be null
    * @exception IllegalArgumentException if add a node to a leave 
                                          or node to be added is not a leaf
    */
@@ -342,9 +355,8 @@ public class NetworkTopology {
   }
     
   /** Remove a node
-   * Update node counter & rack counter if necessary
-   * @param node
-   *          node to be removed
+   * Update node counter and rack counter if necessary
+   * @param node node to be removed; can be null
    */ 
   public void remove(Node node) {
     if (node==null) return;
@@ -371,8 +383,7 @@ public class NetworkTopology {
        
   /** Check if the tree contains node <i>node</i>
    * 
-   * @param node
-   *          a node
+   * @param node a node
    * @return true if <i>node</i> is already in the tree; false otherwise
    */
   public boolean contains(Node node) {
@@ -380,10 +391,11 @@ public class NetworkTopology {
     netlock.readLock().lock();
     try {
       Node parent = node.getParent();
-      for(int level=node.getLevel(); parent!=null&&level>0;
-          parent=parent.getParent(), level--) {
-        if (parent == clusterMap)
+      for (int level = node.getLevel(); parent != null && level > 0;
+           parent = parent.getParent(), level--) {
+        if (parent == clusterMap) {
           return true;
+        }
       }
     } finally {
       netlock.readLock().unlock();
@@ -409,7 +421,7 @@ public class NetworkTopology {
     }
   }
     
-  /** Return the total number of racks */
+  /** @return the total number of racks */
   public int getNumOfRacks() {
     netlock.readLock().lock();
     try {
@@ -419,7 +431,7 @@ public class NetworkTopology {
     }
   }
     
-  /** Return the total number of nodes */
+  /** @return the total number of leaf nodes */
   public int getNumOfLeaves() {
     netlock.readLock().lock();
     try {
@@ -432,11 +444,11 @@ public class NetworkTopology {
   /** Return the distance between two nodes
    * It is assumed that the distance from one node to its parent is 1
    * The distance between two nodes is calculated by summing up their distances
-   * to their closest common  ancestor.
+   * to their closest common ancestor.
    * @param node1 one node
    * @param node2 another node
-   * @return the distance between node1 and node2
-   * node1 or node2 do not belong to the cluster
+   * @return the distance between node1 and node2 which is zero if they are the same
+   *  or {@link Integer#MAX_VALUE} if node1 or node2 do not belong to the cluster
    */
   public int getDistance(Node node1, Node node2) {
     if (node1 == node2) {
@@ -477,8 +489,8 @@ public class NetworkTopology {
   } 
     
   /** Check if two nodes are on the same rack
-   * @param node1 one node
-   * @param node2 another node
+   * @param node1 one node (can be null)
+   * @param node2 another node (can be null)
    * @return true if node1 and node2 are on the same rack; false otherwise
    * @exception IllegalArgumentException when either node1 or node2 is null, or
    * node1 or node2 do not belong to the cluster
@@ -622,6 +634,8 @@ public class NetworkTopology {
    * If neither local node or local rack node is found, put a random replica
    * location at position 0.
    * It leaves the rest nodes untouched.
+   * @param reader the node that wishes to read a block from one of the nodes
+   * @param nodes the list of nodes containing data for the reader
    */
   public void pseudoSortByDistance( Node reader, Node[] nodes ) {
     int tempIndex = 0;

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/Node.java

@@ -33,20 +33,31 @@ import org.apache.hadoop.classification.InterfaceStability;
 @InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
 @InterfaceStability.Unstable
 public interface Node {
-  /** Return the string representation of this node's network location */
+  /** @return the string representation of this node's network location */
   public String getNetworkLocation();
-  /** Set the node's network location */
+
+  /** Set this node's network location
+   * @param location the location
+   */
   public void setNetworkLocation(String location);
-  /** Return this node's name */
+  /** @return this node's name */
   public String getName();
-  /** Return this node's parent */
+
+  /** @return this node's parent */
   public Node getParent();
-  /** Set this node's parent */
+
+  /** Set this node's parent
+   * @param parent the parent
+   */
   public void setParent(Node parent);
-  /** Return this node's level in the tree.
+
+  /** @return this node's level in the tree.
    * E.g. the root of a tree returns 0 and its children return 1
    */
   public int getLevel();
-  /** Set this node's level in the tree.*/
+
+  /** Set this node's level in the tree
+   * @param i the level
+   */
   public void setLevel(int i);
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/NodeBase.java

@@ -27,9 +27,12 @@ import org.apache.hadoop.classification.InterfaceStability;
 @InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
 @InterfaceStability.Unstable
 public class NodeBase implements Node {
+  /** Path separator {@value} */
   public final static char PATH_SEPARATOR = '/';
+  /** Path separator as a string {@value} */
   public final static String PATH_SEPARATOR_STR = "/";
-  public final static String ROOT = ""; // string representation of root
+  /** string representation of root {@value} */
+  public final static String ROOT = "";
   
   protected String name; //host:port#
   protected String location; //string representation of this node's location
@@ -55,7 +58,7 @@ public class NodeBase implements Node {
   }
   
   /** Construct a node from its name and its location
-   * @param name this node's name 
+   * @param name this node's name (can be null, must not contain {@link #PATH_SEPARATOR})
    * @param location this node's location 
    */
   public NodeBase(String name, String location) {
@@ -63,7 +66,7 @@ public class NodeBase implements Node {
   }
   
   /** Construct a node from its name and its location
-   * @param name this node's name 
+   * @param name this node's name (can be null, must not contain {@link #PATH_SEPARATOR})
    * @param location this node's location 
    * @param parent this node's parent node
    * @param level this node's level in the tree
@@ -74,7 +77,11 @@ public class NodeBase implements Node {
     this.level = level;
   }
 
-  /* set this node's name and location */
+  /**
+   * set this node's name and location
+   * @param name the (nullable) name -which cannot contain the {@link #PATH_SEPARATOR}
+   * @param location the location
+   */
   private void set(String name, String location) {
     if (name != null && name.contains(PATH_SEPARATOR_STR))
       throw new IllegalArgumentException(
@@ -83,27 +90,43 @@ public class NodeBase implements Node {
     this.location = location;      
   }
   
-  /** Return this node's name */
+  /** @return this node's name */
+  @Override
   public String getName() { return name; }
   
-  /** Return this node's network location */
+  /** @return this node's network location */
+  @Override
   public String getNetworkLocation() { return location; }
   
-  /** Set this node's network location */
+  /** Set this node's network location
+   * @param location the location
+   */
+  @Override
   public void setNetworkLocation(String location) { this.location = location; }
   
-  /** Return this node's path */
+  /**
+   * Get the path of a node
+   * @param node a non-null node
+   * @return the path of a node
+   */
   public static String getPath(Node node) {
     return node.getNetworkLocation()+PATH_SEPARATOR_STR+node.getName();
   }
   
-  /** Return this node's string representation */
+  /** @return this node's path as its string representation */
+  @Override
   public String toString() {
     return getPath(this);
   }
 
-  /** Normalize a path */
-  static public String normalize(String path) {
+  /** Normalize a path by stripping off any trailing {@link #PATH_SEPARATOR}
+   * @param path path to normalize.
+   * @return the normalised path
+   * If <i>path</i>is null or empty {@link #ROOT} is returned
+   * @throws IllegalArgumentException if the first character of a non empty path
+   * is not {@link #PATH_SEPARATOR}
+   */
+  public static String normalize(String path) {
     if (path == null || path.length() == 0) return ROOT;
     
     if (path.charAt(0) != PATH_SEPARATOR) {
@@ -119,20 +142,28 @@ public class NodeBase implements Node {
     return path;
   }
   
-  /** Return this node's parent */
+  /** @return this node's parent */
+  @Override
   public Node getParent() { return parent; }
   
-  /** Set this node's parent */
+  /** Set this node's parent
+   * @param parent the parent
+   */
+  @Override
   public void setParent(Node parent) {
     this.parent = parent;
   }
   
-  /** Return this node's level in the tree.
+  /** @return this node's level in the tree.
    * E.g. the root of a tree returns 0 and its children return 1
    */
+  @Override
   public int getLevel() { return level; }
   
-  /** Set this node's level in the tree */
+  /** Set this node's level in the tree
+   * @param level the level
+   */
+  @Override
   public void setLevel(int level) {
     this.level = level;
   }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/net/ScriptBasedMapping.java

@@ -32,7 +32,7 @@ import org.apache.hadoop.fs.CommonConfigurationKeys;
 
 /**
  * This class implements the {@link DNSToSwitchMapping} interface using a 
- * script configured via net.topology.script.file.name .
+ * script configured via the {@link CommonConfigurationKeys#NET_TOPOLOGY_SCRIPT_FILE_NAME_KEY}
  */
 @InterfaceAudience.Public
 @InterfaceStability.Evolving
@@ -42,50 +42,86 @@ implements Configurable
   public ScriptBasedMapping() {
     super(new RawScriptBasedMapping());
   }
-  
-  // script must accept at least this many args
+
+  /**
+   * Minimum number of arguments: {@value}
+   */
   static final int MIN_ALLOWABLE_ARGS = 1;
-  
+
+  /**
+   * Default number of arguments: {@value}
+   */
   static final int DEFAULT_ARG_COUNT = 
                      CommonConfigurationKeys.NET_TOPOLOGY_SCRIPT_NUMBER_ARGS_DEFAULT;
-  
+
+  /**
+   * key to the script filename {@value}
+   */
   static final String SCRIPT_FILENAME_KEY = 
                      CommonConfigurationKeys.NET_TOPOLOGY_SCRIPT_FILE_NAME_KEY ;
-  static final String SCRIPT_ARG_COUNT_KEY = 
+  /**
+   * key to the argument count that the script supports
+   */
+  static final String SCRIPT_ARG_COUNT_KEY =
                      CommonConfigurationKeys.NET_TOPOLOGY_SCRIPT_NUMBER_ARGS_KEY ;
-  
+
+  /**
+   * Create an instance from the given configuration
+   * @param conf configuration
+   */
   public ScriptBasedMapping(Configuration conf) {
     this();
     setConf(conf);
   }
-  
+
+  @Override
   public Configuration getConf() {
     return ((RawScriptBasedMapping)rawMapping).getConf();
   }
-  
+
+  @Override
   public void setConf(Configuration conf) {
     ((RawScriptBasedMapping)rawMapping).setConf(conf);
   }
-  
+
+  /**
+   * This is the uncached script mapping that is fed into the cache managed
+   * by the superclass {@link CachedDNSToSwitchMapping}
+   */
   private static final class RawScriptBasedMapping
-  implements DNSToSwitchMapping {
-  private String scriptName;
-  private Configuration conf;
-  private int maxArgs; //max hostnames per call of the script
-  private static Log LOG = 
-    LogFactory.getLog(ScriptBasedMapping.class);
-  public void setConf (Configuration conf) {
-    this.scriptName = conf.get(SCRIPT_FILENAME_KEY);
-    this.maxArgs = conf.getInt(SCRIPT_ARG_COUNT_KEY, DEFAULT_ARG_COUNT);
-    this.conf = conf;
-  }
-  public Configuration getConf () {
-    return conf;
-  }
-  
-  public RawScriptBasedMapping() {}
-  
-  public List<String> resolve(List<String> names) {
+      implements DNSToSwitchMapping {
+    private String scriptName;
+    private Configuration conf;
+    private int maxArgs; //max hostnames per call of the script
+    private static Log LOG =
+        LogFactory.getLog(ScriptBasedMapping.class);
+
+    /**
+     * Set the configuration and
+     * @param conf extract the configuration parameters of interest
+     */
+    public void setConf (Configuration conf) {
+      this.scriptName = conf.get(SCRIPT_FILENAME_KEY);
+      this.maxArgs = conf.getInt(SCRIPT_ARG_COUNT_KEY, DEFAULT_ARG_COUNT);
+      this.conf = conf;
+    }
+
+    /**
+     * Get the configuration
+     * @return the configuration
+     */
+    public Configuration getConf () {
+      return conf;
+    }
+
+    /**
+     * Constructor. The mapping is not ready to use until
+     * {@link #setConf(Configuration)} has been called
+     */
+    public RawScriptBasedMapping() {}
+
+    @Override
+    public List<String> resolve(List<String> names) {
     List <String> m = new ArrayList<String>(names.size());
     
     if (names.isEmpty()) {
@@ -123,45 +159,53 @@ implements Configurable
     return m;
   }
 
-  private String runResolveCommand(List<String> args) {
-    int loopCount = 0;
-    if (args.size() == 0) {
-      return null;
-    }
-    StringBuilder allOutput = new StringBuilder();
-    int numProcessed = 0;
-    if (maxArgs < MIN_ALLOWABLE_ARGS) {
-      LOG.warn("Invalid value " + Integer.toString(maxArgs)
-          + " for " + SCRIPT_ARG_COUNT_KEY + "; must be >= "
-          + Integer.toString(MIN_ALLOWABLE_ARGS));
-      return null;
-    }
-    
-    while (numProcessed != args.size()) {
-      int start = maxArgs * loopCount;
-      List <String> cmdList = new ArrayList<String>();
-      cmdList.add(scriptName);
-      for (numProcessed = start; numProcessed < (start + maxArgs) && 
-           numProcessed < args.size(); numProcessed++) {
-        cmdList.add(args.get(numProcessed)); 
-      }
-      File dir = null;
-      String userDir;
-      if ((userDir = System.getProperty("user.dir")) != null) {
-        dir = new File(userDir);
-      }
-      ShellCommandExecutor s = new ShellCommandExecutor(
-                                   cmdList.toArray(new String[0]), dir);
-      try {
-        s.execute();
-        allOutput.append(s.getOutput() + " ");
-      } catch (Exception e) {
-        LOG.warn("Exception: ", e);
+    /**
+     * Build and execute the resolution command. The command is
+     * executed in the directory specified by the system property
+     * "user.dir" if set; otherwise the current working directory is used
+     * @param args a list of arguments
+     * @return null if the number of arguments is out of range,
+     * or the output of the command.
+     */
+    private String runResolveCommand(List<String> args) {
+      int loopCount = 0;
+      if (args.size() == 0) {
         return null;
       }
-      loopCount++; 
+      StringBuilder allOutput = new StringBuilder();
+      int numProcessed = 0;
+      if (maxArgs < MIN_ALLOWABLE_ARGS) {
+        LOG.warn("Invalid value " + Integer.toString(maxArgs)
+            + " for " + SCRIPT_ARG_COUNT_KEY + "; must be >= "
+            + Integer.toString(MIN_ALLOWABLE_ARGS));
+        return null;
+      }
+
+      while (numProcessed != args.size()) {
+        int start = maxArgs * loopCount;
+        List<String> cmdList = new ArrayList<String>();
+        cmdList.add(scriptName);
+        for (numProcessed = start; numProcessed < (start + maxArgs) &&
+            numProcessed < args.size(); numProcessed++) {
+          cmdList.add(args.get(numProcessed));
+        }
+        File dir = null;
+        String userDir;
+        if ((userDir = System.getProperty("user.dir")) != null) {
+          dir = new File(userDir);
+        }
+        ShellCommandExecutor s = new ShellCommandExecutor(
+            cmdList.toArray(new String[0]), dir);
+        try {
+          s.execute();
+          allOutput.append(s.getOutput() + " ");
+        } catch (Exception e) {
+          LOG.warn("Exception: ", e);
+          return null;
+        }
+        loopCount++;
+      }
+      return allOutput.toString();
     }
-    return allOutput.toString();
-  }
   }
 }