/** Gets the median timestamp of the last 11 blocks */
private static long getMedianTimestampOfRecentBlocks(StoredBlock storedBlock, BlockStore store)
throws BlockStoreException {
long[] timestamps = new long[11];
int unused = 9;
timestamps[10] = storedBlock.getHeader().getTimeSeconds();
while (unused >= 0 && (storedBlock = storedBlock.getPrev(store)) != null)
timestamps[unused--] = storedBlock.getHeader().getTimeSeconds();
Arrays.sort(timestamps, unused + 1, 11);
return timestamps[unused + (11 - unused) / 2];
}
/**
* Returns an estimate of when the given block will be reached, assuming a perfect 10 minute
* average for each block. This is useful for turning transaction lock times into human readable
* times. Note that a height in the past will still be estimated, even though the time of solving
* is actually known (we won't scan backwards through the chain to obtain the right answer).
*/
public Date estimateBlockTime(int height) {
synchronized (chainHeadLock) {
long offset = height - chainHead.getHeight();
long headTime = chainHead.getHeader().getTimeSeconds();
long estimated =
(headTime * 1000) + (1000L * 30L * 1L * offset); // 2 blocks per minute
return new Date(estimated);
}
}
/** Constructs a BlockChain connected to the given list of listeners (eg, wallets) and a store. */
public AbstractBlockChain(
Context context, List<BlockChainListener> listeners, BlockStore blockStore)
throws BlockStoreException {
this.blockStore = blockStore;
chainHead = blockStore.getChainHead();
log.info("chain head is at height {}:\n{}", chainHead.getHeight(), chainHead.getHeader());
this.params = context.getParams();
this.listeners = new CopyOnWriteArrayList<ListenerRegistration<BlockChainListener>>();
for (BlockChainListener l : listeners) addListener(l, Threading.SAME_THREAD);
}
@Override
public void setChainHead(StoredBlock chainHead) throws BlockStoreException {
final MappedByteBuffer buffer = this.buffer;
if (buffer == null) throw new BlockStoreException("Store closed");
lock.lock();
try {
lastChainHead = chainHead;
byte[] headHash = chainHead.getHeader().getHash().getBytes();
buffer.position(8);
buffer.put(headHash);
} finally {
lock.unlock();
}
}
@Override
public void put(StoredBlock block) throws BlockStoreException {
final MappedByteBuffer buffer = this.buffer;
if (buffer == null) throw new BlockStoreException("Store closed");
lock.lock();
try {
int cursor = getRingCursor(buffer);
if (cursor == getFileSize()) {
// Wrapped around.
cursor = FILE_PROLOGUE_BYTES;
}
buffer.position(cursor);
Sha256Hash hash = block.getHeader().getHash();
notFoundCache.remove(hash);
buffer.put(hash.getBytes());
block.serializeCompact(buffer);
setRingCursor(buffer, buffer.position());
blockCache.put(hash, block);
} finally {
lock.unlock();
}
}
/**
* Called as part of connecting a block when the new block results in a different chain having
* higher total work.
*
* <p>if (shouldVerifyTransactions) Either newChainHead needs to be in the block store as a
* FullStoredBlock, or (block != null && block.transactions != null)
*/
private void handleNewBestChain(
StoredBlock storedPrev, StoredBlock newChainHead, Block block, boolean expensiveChecks)
throws BlockStoreException, VerificationException, PrunedException {
checkState(lock.isHeldByCurrentThread());
// This chain has overtaken the one we currently believe is best. Reorganize is required.
//
// Firstly, calculate the block at which the chain diverged. We only need to examine the
// chain from beyond this block to find differences.
StoredBlock head = getChainHead();
final StoredBlock splitPoint = findSplit(newChainHead, head, blockStore);
log.info("Re-organize after split at height {}", splitPoint.getHeight());
log.info("Old chain head: {}", head.getHeader().getHashAsString());
log.info("New chain head: {}", newChainHead.getHeader().getHashAsString());
log.info("Split at block: {}", splitPoint.getHeader().getHashAsString());
// Then build a list of all blocks in the old part of the chain and the new part.
final LinkedList<StoredBlock> oldBlocks = getPartialChain(head, splitPoint, blockStore);
final LinkedList<StoredBlock> newBlocks = getPartialChain(newChainHead, splitPoint, blockStore);
// Disconnect each transaction in the previous main chain that is no longer in the new main
// chain
StoredBlock storedNewHead = splitPoint;
if (shouldVerifyTransactions()) {
for (StoredBlock oldBlock : oldBlocks) {
try {
disconnectTransactions(oldBlock);
} catch (PrunedException e) {
// We threw away the data we need to re-org this deep! We need to go back to a peer with
// full
// block contents and ask them for the relevant data then rebuild the indexs. Or we could
// just
// give up and ask the human operator to help get us unstuck (eg, rescan from the genesis
// block).
// TODO: Retry adding this block when we get a block with hash e.getHash()
throw e;
}
}
StoredBlock cursor;
// Walk in ascending chronological order.
for (Iterator<StoredBlock> it = newBlocks.descendingIterator(); it.hasNext(); ) {
cursor = it.next();
Block cursorBlock = cursor.getHeader();
if (expensiveChecks
&& cursorBlock.getTimeSeconds()
<= getMedianTimestampOfRecentBlocks(cursor.getPrev(blockStore), blockStore))
throw new VerificationException("Block's timestamp is too early during reorg");
TransactionOutputChanges txOutChanges;
if (cursor != newChainHead || block == null) txOutChanges = connectTransactions(cursor);
else txOutChanges = connectTransactions(newChainHead.getHeight(), block);
storedNewHead = addToBlockStore(storedNewHead, cursorBlock.cloneAsHeader(), txOutChanges);
}
} else {
// (Finally) write block to block store
storedNewHead = addToBlockStore(storedPrev, newChainHead.getHeader());
}
// Now inform the listeners. This is necessary so the set of currently active transactions (that
// we can spend)
// can be updated to take into account the re-organize. We might also have received new coins we
// didn't have
// before and our previous spends might have been undone.
for (final ListenerRegistration<BlockChainListener> registration : listeners) {
if (registration.executor == Threading.SAME_THREAD) {
// Short circuit the executor so we can propagate any exceptions.
// TODO: Do we really need to do this or should it be irrelevant?
registration.listener.reorganize(splitPoint, oldBlocks, newBlocks);
} else {
registration.executor.execute(
new Runnable() {
@Override
public void run() {
try {
registration.listener.reorganize(splitPoint, oldBlocks, newBlocks);
} catch (VerificationException e) {
log.error("Block chain listener threw exception during reorg", e);
}
}
});
}
}
// Update the pointer to the best known block.
setChainHead(storedNewHead);
}
// expensiveChecks enables checks that require looking at blocks further back in the chain
// than the previous one when connecting (eg median timestamp check)
// It could be exposed, but for now we just set it to shouldVerifyTransactions()
private void connectBlock(
final Block block,
StoredBlock storedPrev,
boolean expensiveChecks,
@Nullable final List<Sha256Hash> filteredTxHashList,
@Nullable final Map<Sha256Hash, Transaction> filteredTxn)
throws BlockStoreException, VerificationException, PrunedException {
checkState(lock.isHeldByCurrentThread());
boolean filtered = filteredTxHashList != null && filteredTxn != null;
// Check that we aren't connecting a block that fails a checkpoint check
if (!params.passesCheckpoint(storedPrev.getHeight() + 1, block.getHash()))
throw new VerificationException(
"Block failed checkpoint lockin at " + (storedPrev.getHeight() + 1));
if (shouldVerifyTransactions()) {
checkNotNull(block.transactions);
for (Transaction tx : block.transactions)
if (!tx.isFinal(storedPrev.getHeight() + 1, block.getTimeSeconds()))
throw new VerificationException("Block contains non-final transaction");
}
StoredBlock head = getChainHead();
if (storedPrev.equals(head)) {
if (filtered && filteredTxn.size() > 0) {
log.debug(
"Block {} connects to top of best chain with {} transaction(s) of which we were sent {}",
block.getHashAsString(),
filteredTxHashList.size(),
filteredTxn.size());
for (Sha256Hash hash : filteredTxHashList) log.debug(" matched tx {}", hash);
}
if (expensiveChecks
&& block.getTimeSeconds() <= getMedianTimestampOfRecentBlocks(head, blockStore))
throw new VerificationException("Block's timestamp is too early");
// This block connects to the best known block, it is a normal continuation of the system.
TransactionOutputChanges txOutChanges = null;
if (shouldVerifyTransactions())
txOutChanges = connectTransactions(storedPrev.getHeight() + 1, block);
StoredBlock newStoredBlock =
addToBlockStore(
storedPrev, block.transactions == null ? block : block.cloneAsHeader(), txOutChanges);
setChainHead(newStoredBlock);
log.debug("Chain is now {} blocks high, running listeners", newStoredBlock.getHeight());
informListenersForNewBlock(
block, NewBlockType.BEST_CHAIN, filteredTxHashList, filteredTxn, newStoredBlock);
} else {
// This block connects to somewhere other than the top of the best known chain. We treat these
// differently.
//
// Note that we send the transactions to the wallet FIRST, even if we're about to re-organize
// this block
// to become the new best chain head. This simplifies handling of the re-org in the Wallet
// class.
StoredBlock newBlock = storedPrev.build(block);
boolean haveNewBestChain = newBlock.moreWorkThan(head);
if (haveNewBestChain) {
log.info("Block is causing a re-organize");
} else {
StoredBlock splitPoint = findSplit(newBlock, head, blockStore);
if (splitPoint != null && splitPoint.equals(newBlock)) {
// newStoredBlock is a part of the same chain, there's no fork. This happens when we
// receive a block
// that we already saw and linked into the chain previously, which isn't the chain head.
// Re-processing it is confusing for the wallet so just skip.
log.warn(
"Saw duplicated block in main chain at height {}: {}",
newBlock.getHeight(),
newBlock.getHeader().getHash());
return;
}
if (splitPoint == null) {
// This should absolutely never happen
// (lets not write the full block to disk to keep any bugs which allow this to happen
// from writing unreasonable amounts of data to disk)
throw new VerificationException("Block forks the chain but splitPoint is null");
} else {
// We aren't actually spending any transactions (yet) because we are on a fork
addToBlockStore(storedPrev, block);
int splitPointHeight = splitPoint.getHeight();
String splitPointHash = splitPoint.getHeader().getHashAsString();
log.info(
"Block forks the chain at height {}/block {}, but it did not cause a reorganize:\n{}",
splitPointHeight,
splitPointHash,
newBlock.getHeader().getHashAsString());
}
}
// We may not have any transactions if we received only a header, which can happen during fast
// catchup.
// If we do, send them to the wallet but state that they are on a side chain so it knows not
// to try and
// spend them until they become activated.
if (block.transactions != null || filtered) {
informListenersForNewBlock(
block, NewBlockType.SIDE_CHAIN, filteredTxHashList, filteredTxn, newBlock);
}
if (haveNewBestChain) handleNewBestChain(storedPrev, newBlock, block, expensiveChecks);
}
}