Reformat log messages in DnsDiscovery and add one log message for the…

… success case, to make more clear what's going on.

Also, rename hostNames to dnsSeeds as this name is more speaking for itself, and is used in other places as well.

core/src/main/java/com/google/bitcoin/net/discovery/DnsDiscovery.java

@@ -1,5 +1,6 @@
 /**
  * Copyright 2011 John Sample
+ * Copyright 2014 Andreas Schildbach
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -40,7 +41,7 @@
 public class DnsDiscovery implements PeerDiscovery {
     private static final Logger log = LoggerFactory.getLogger(DnsDiscovery.class);
 
-    private final String[] hostNames;
+    private final String[] dnsSeeds;
     private final NetworkParameters netParams;
 
     /**
@@ -55,42 +56,44 @@ public DnsDiscovery(NetworkParameters netParams) {
     /**
      * Supports finding peers through DNS A records.
      *
-     * @param hostNames Host names to be examined for seed addresses.
+     * @param dnsSeeds Host names to be examined for seed addresses.
      * @param netParams Network parameters to be used for port information.
      */
-    public DnsDiscovery(String[] hostNames, NetworkParameters netParams) {
-        this.hostNames = hostNames;
+    public DnsDiscovery(String[] dnsSeeds, NetworkParameters netParams) {
+        this.dnsSeeds = dnsSeeds;
         this.netParams = netParams;
     }
 
     public InetSocketAddress[] getPeers(long timeoutValue, TimeUnit timeoutUnit) throws PeerDiscoveryException {
-        if (hostNames == null)
-            throw new PeerDiscoveryException("Unable to find any peers via DNS");
+        if (dnsSeeds == null || dnsSeeds.length == 0)
+            throw new PeerDiscoveryException("No DNS seeds configured; unable to find any peers");
 
         // Java doesn't have an async DNS API so we have to do all lookups in a thread pool, as sometimes seeds go
         // hard down and it takes ages to give up and move on.
-        ExecutorService threadPool = Executors.newFixedThreadPool(hostNames.length);
+        ExecutorService threadPool = Executors.newFixedThreadPool(dnsSeeds.length);
         try {
             List<Callable<InetAddress[]>> tasks = Lists.newArrayList();
-            for (final String seed : hostNames)
+            for (final String seed : dnsSeeds) {
                 tasks.add(new Callable<InetAddress[]>() {
                     public InetAddress[] call() throws Exception {
                         return InetAddress.getAllByName(seed);
                     }
                 });
+            }
             final List<Future<InetAddress[]>> futures = threadPool.invokeAll(tasks, timeoutValue, timeoutUnit);
             ArrayList<InetSocketAddress> addrs = Lists.newArrayList();
             for (int i = 0; i < futures.size(); i++) {
                 Future<InetAddress[]> future = futures.get(i);
                 if (future.isCancelled()) {
-                    log.warn("{} timed out", hostNames[i]);
+                    log.warn("DNS seed {}: timed out", dnsSeeds[i]);
                     continue;  // Timed out.
                 }
                 final InetAddress[] inetAddresses;
                 try {
                     inetAddresses = future.get();
+                    log.info("DNS seed {}: got {} peers", dnsSeeds[i], inetAddresses.length);
                 } catch (ExecutionException e) {
-                    log.error("Failed to look up DNS seeds from {}: {}", hostNames[i], e.getMessage());
+                    log.error("DNS seed {}: failed to look up: {}", dnsSeeds[i], e.getMessage());
                     continue;
                 }
                 for (InetAddress addr : inetAddresses) {