Modified BlockMinter.higherWeightChainExists() so that it checks for invalid blocks before treating a chain as higher weight. Otherwise minting is slowed down when a higher weight but invalid chain exists on the network (e.g. after a hard fork).

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

@@ -571,25 +571,29 @@ public class BlockMinter extends Thread {
 
 		List<Peer> peers = Network.getInstance().getImmutableHandshakedPeers();
 		// Loop through handshaked peers and check for any new block candidates
-		// TODO: filter out peers with invalid blocks
 		for (Peer peer : peers) {
 			if (peer.getCommonBlockData() != null && peer.getCommonBlockData().getCommonBlockSummary() != null) {
 				// This peer has common block data
 				CommonBlockData commonBlockData = peer.getCommonBlockData();
 				BlockSummaryData commonBlockSummaryData = commonBlockData.getCommonBlockSummary();
-				if (commonBlockData.getChainWeight() != null) {
+				if (commonBlockData.getChainWeight() != null && peer.getCommonBlockData().getBlockSummariesAfterCommonBlock() != null) {
 					// The synchronizer has calculated this peer's chain weight
+					if (!Synchronizer.getInstance().containsInvalidBlockSummary(peer.getCommonBlockData().getBlockSummariesAfterCommonBlock())) {
+						// .. and it doesn't hold any invalid blocks
 						BigInteger ourChainWeightSinceCommonBlock = this.getOurChainWeightSinceBlock(repository, commonBlockSummaryData, commonBlockData.getBlockSummariesAfterCommonBlock());
 						BigInteger ourChainWeight = ourChainWeightSinceCommonBlock.add(blockCandidateWeight);
 						BigInteger peerChainWeight = commonBlockData.getChainWeight();
 						if (peerChainWeight.compareTo(ourChainWeight) >= 0) {
 							// This peer has a higher weight chain than ours
-						LOGGER.debug("Peer {} is on a higher weight chain ({}) than ours ({})", peer, formatter.format(peerChainWeight), formatter.format(ourChainWeight));
+							LOGGER.info("Peer {} is on a higher weight chain ({}) than ours ({})", peer, formatter.format(peerChainWeight), formatter.format(ourChainWeight));
 							return true;
 
 						} else {
 							LOGGER.debug("Peer {} is on a lower weight chain ({}) than ours ({})", peer, formatter.format(peerChainWeight), formatter.format(ourChainWeight));
 						}
+					} else {
+						LOGGER.debug("Peer {} has an invalid block", peer);
+					}
 				} else {
 					LOGGER.debug("Peer {} has no chain weight", peer);
 				}

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

@@ -874,7 +874,7 @@ public class Synchronizer extends Thread {
 			}
 		}
 	}
-	private boolean containsInvalidBlockSummary(List<BlockSummaryData> blockSummaries) {
+	public boolean containsInvalidBlockSummary(List<BlockSummaryData> blockSummaries) {
 		if (blockSummaries == null || invalidBlockSignatures == null) {
 			return false;
 		}