Improved logging, to give a clearer picture of the peer selection decisions.

src/main/java/org/qortal/controller/Controller.java

@@ -669,11 +669,18 @@ public class Controller extends Thread {
 
 		final int peersRemoved = peersBeforeComparison - peers.size();
 		if (peersRemoved > 0)
-			LOGGER.debug(String.format("Ignoring %d peers on inferior chains. Peers remaining: %d", peersRemoved, peers.size()));
+			LOGGER.info(String.format("Ignoring %d peers on inferior chains. Peers remaining: %d", peersRemoved, peers.size()));
 
 		if (peers.isEmpty())
 			return;
 
+		if (peers.size() > 1) {
+			StringBuilder finalPeersString = new StringBuilder();
+			for (Peer peer : peers)
+				finalPeersString = finalPeersString.length() > 0 ? finalPeersString.append(", ").append(peer) : finalPeersString.append(peer);
+			LOGGER.info(String.format("Choosing random peer from: [%s]", finalPeersString.toString()));
+		}
+
 		// Pick random peer to sync with
 		int index = new SecureRandom().nextInt(peers.size());
 		Peer peer = peers.get(index);

src/main/java/org/qortal/controller/Synchronizer.java

@@ -334,6 +334,7 @@ public class Synchronizer {
 						ourChainWeight = Block.calcChainWeight(commonBlockSummary.getHeight(), commonBlockSummary.getSignature(), ourBlockSummaries, minChainLength);
 
 					NumberFormat formatter = new DecimalFormat("0.###E0");
+					NumberFormat accurateFormatter = new DecimalFormat("0.################E0");
 					LOGGER.debug(String.format("Our chain weight based on %d blocks is %s", ourBlockSummaries.size(), formatter.format(ourChainWeight)));
 
 					LOGGER.debug(String.format("Listing peers with common block %.8s...", Base58.encode(commonBlockSummary.getSignature())));
@@ -383,7 +384,8 @@ public class Synchronizer {
 						for (Peer peer : superiorPeersForComparison) {
 							// Check if we should discard an inferior peer
 							if (peer.getCommonBlockData().getChainWeight().compareTo(bestChainWeight) < 0) {
-								LOGGER.debug(String.format("Peer %s has a lower chain weight than other peer(s) in this group - removing it from this round.", peer));
+								BigInteger difference = bestChainWeight.subtract(peer.getCommonBlockData().getChainWeight());
+								LOGGER.debug(String.format("Peer %s has a lower chain weight (difference: %s) than other peer(s) in this group - removing it from this round.", peer, accurateFormatter.format(difference)));
 								peers.remove(peer);
 							}
 						}