Experimental idea to prevent a single node signing more than one block in a row.

This could drastically reduce the number of forks being created. Currently, if a node is having problems syncing, it will continue adding to its own fork, which adds confusion to the network. With this new idea, the node would be prevented from adding to its own chain and is instead forced to wait until it has retrieved the next block from the network.

We will need to test this on the testnet very carefully. My worry is that, because all minters submit blocks, it could create a situation where the first block is submitted by everyone, and the second block is submitted by no-one, until a different candidate for the first block has been obtained from a peer. This may not be a problem at all, and could actually improve stability in a huge way, but at the same time it has the potential to introduce serious network problems if we are not careful.

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

@@ -165,6 +165,14 @@ public class BlockMinter extends Thread {
 				// Do we need to build any potential new blocks?
 				List<PrivateKeyAccount> newBlocksMintingAccounts = mintingAccountsData.stream().map(accountData -> new PrivateKeyAccount(repository, accountData.getPrivateKey())).collect(Collectors.toList());
 
+				// We might need to sit the next block out, if one of our minting accounts signed the previous one
+				final byte[] previousBlockMinter = previousBlockData.getMinterPublicKey();
+				final boolean mintedLastBlock = mintingAccountsData.stream().anyMatch(mintingAccount -> Arrays.equals(mintingAccount.getPublicKey(), previousBlockMinter));
+				if (mintedLastBlock) {
+					LOGGER.trace(String.format("One of our keys signed the last block, so we won't sign the next one"));
+					continue;
+				}
+
 				for (PrivateKeyAccount mintingAccount : newBlocksMintingAccounts) {
 					// First block does the AT heavy-lifting
 					if (newBlocks.isEmpty()) {