def __init__(self, env, db, daemon, notifications):
self.env = env
self.db = db
self.daemon = daemon
self.notifications = notifications
self.coin = env.coin
self.blocks_event = asyncio.Event()
self.prefetcher = Prefetcher(daemon, env.coin, self.blocks_event)
self.logger = class_logger(__name__, self.__class__.__name__)
self.executor = ThreadPoolExecutor(1)
# Meta
self.next_cache_check = 0
self.touched = set()
self.reorg_count = 0
# Caches of unflushed items.
self.headers = []
self.block_hashes = []
self.block_txs = []
self.undo_infos = []
# UTXO cache
self.utxo_cache = {}
self.db_deletes = []
# If the lock is successfully acquired, in-memory chain state
# is consistent with self.height
self.state_lock = asyncio.Lock()
self.search_cache = {}
self.history_cache = {}
self.status_server = StatusServer()
async def _make_udp_server(self, port, latency) -> StatusServer:
s = StatusServer()
await s.start(0, b'\x00' * 32, 'US', '127.0.0.1', port, True)
s.set_available()
sendto = s._protocol.transport.sendto
def mock_sendto(data, addr):
self.loop.call_later(latency, sendto, data, addr)
s._protocol.transport.sendto = mock_sendto
self.addCleanup(s.stop)
return s
class BlockProcessor:
"""Process blocks and update the DB state to match.
Employ a prefetcher to prefetch blocks in batches for processing.
Coordinate backing up in case of chain reorganisations.
"""
block_count_metric = Gauge("block_count",
"Number of processed blocks",
namespace=NAMESPACE)
block_update_time_metric = Histogram("block_time",
"Block update times",
namespace=NAMESPACE,
buckets=HISTOGRAM_BUCKETS)
reorg_count_metric = Gauge("reorg_count",
"Number of reorgs",
namespace=NAMESPACE)
def __init__(self, env, db, daemon, notifications):
self.env = env
self.db = db
self.daemon = daemon
self.notifications = notifications
self.coin = env.coin
self.blocks_event = asyncio.Event()
self.prefetcher = Prefetcher(daemon, env.coin, self.blocks_event)
self.logger = class_logger(__name__, self.__class__.__name__)
self.executor = ThreadPoolExecutor(1)
# Meta
self.next_cache_check = 0
self.touched = set()
self.reorg_count = 0
# Caches of unflushed items.
self.headers = []
self.block_hashes = []
self.block_txs = []
self.undo_infos = []
# UTXO cache
self.utxo_cache = {}
self.db_deletes = []
# If the lock is successfully acquired, in-memory chain state
# is consistent with self.height
self.state_lock = asyncio.Lock()
self.search_cache = {}
self.history_cache = {}
self.status_server = StatusServer()
async def run_in_thread_with_lock(self, func, *args):
# Run in a thread to prevent blocking. Shielded so that
# cancellations from shutdown don't lose work - when the task
# completes the data will be flushed and then we shut down.
# Take the state lock to be certain in-memory state is
# consistent and not being updated elsewhere.
async def run_in_thread_locked():
async with self.state_lock:
return await asyncio.get_event_loop().run_in_executor(
self.executor, func, *args)
return await asyncio.shield(run_in_thread_locked())
async def check_and_advance_blocks(self, raw_blocks):
"""Process the list of raw blocks passed. Detects and handles
reorgs.
"""
if not raw_blocks:
return
first = self.height + 1
blocks = [
self.coin.block(raw_block, first + n)
for n, raw_block in enumerate(raw_blocks)
]
headers = [block.header for block in blocks]
hprevs = [self.coin.header_prevhash(h) for h in headers]
chain = [self.tip] + [self.coin.header_hash(h) for h in headers[:-1]]
if hprevs == chain:
start = time.perf_counter()
await self.run_in_thread_with_lock(self.advance_blocks, blocks)
if self.sql:
await self.db.search_index.claim_consumer(
self.sql.claim_producer())
for cache in self.search_cache.values():
cache.clear()
self.history_cache.clear()
self.notifications.notified_mempool_txs.clear()
await self._maybe_flush()
processed_time = time.perf_counter() - start
self.block_count_metric.set(self.height)
self.block_update_time_metric.observe(processed_time)
self.status_server.set_height(self.db.fs_height, self.db.db_tip)
if not self.db.first_sync:
s = '' if len(blocks) == 1 else 's'
self.logger.info('processed {:,d} block{} in {:.1f}s'.format(
len(blocks), s, processed_time))
if self._caught_up_event.is_set():
if self.sql:
await self.db.search_index.apply_filters(
self.sql.blocked_streams, self.sql.blocked_channels,
self.sql.filtered_streams, self.sql.filtered_channels)
await self.notifications.on_block(self.touched, self.height)
self.touched = set()
elif hprevs[0] != chain[0]:
await self.reorg_chain()
else:
# It is probably possible but extremely rare that what
# bitcoind returns doesn't form a chain because it
# reorg-ed the chain as it was processing the batched
# block hash requests. Should this happen it's simplest
# just to reset the prefetcher and try again.
self.logger.warning('daemon blocks do not form a chain; '
'resetting the prefetcher')
await self.prefetcher.reset_height(self.height)
async def reorg_chain(self, count: Optional[int] = None):
"""Handle a chain reorganisation.
Count is the number of blocks to simulate a reorg, or None for
a real reorg."""
if count is None:
self.logger.info('chain reorg detected')
else:
self.logger.info(f'faking a reorg of {count:,d} blocks')
async def get_raw_blocks(last_height, hex_hashes):
heights = range(last_height, last_height - len(hex_hashes), -1)
try:
blocks = [
await self.db.read_raw_block(height) for height in heights
]
self.logger.info(f'read {len(blocks)} blocks from disk')
return blocks
except FileNotFoundError:
return await self.daemon.raw_blocks(hex_hashes)
def flush_backup():
# self.touched can include other addresses which is
# harmless, but remove None.
self.touched.discard(None)
self.db.flush_backup(self.flush_data(), self.touched)
try:
await self.flush(True)
start, last, hashes = await self.reorg_hashes(count)
# Reverse and convert to hex strings.
hashes = [hash_to_hex_str(hash) for hash in reversed(hashes)]
self.logger.info("reorg %i block hashes", len(hashes))
for hex_hashes in chunks(hashes, 50):
raw_blocks = await get_raw_blocks(last, hex_hashes)
self.logger.info("got %i raw blocks", len(raw_blocks))
await self.run_in_thread_with_lock(self.backup_blocks,
raw_blocks)
await self.run_in_thread_with_lock(flush_backup)
last -= len(raw_blocks)
await self.prefetcher.reset_height(self.height)
self.reorg_count_metric.inc()
except:
self.logger.exception("boom")
raise
finally:
self.logger.info("done with reorg")
async def reorg_hashes(self, count):
"""Return a pair (start, last, hashes) of blocks to back up during a
reorg.
The hashes are returned in order of increasing height. Start
is the height of the first hash, last of the last.
"""
start, count = await self.calc_reorg_range(count)
last = start + count - 1
s = '' if count == 1 else 's'
self.logger.info(f'chain was reorganised replacing {count:,d} '
f'block{s} at heights {start:,d}-{last:,d}')
return start, last, await self.db.fs_block_hashes(start, count)
async def calc_reorg_range(self, count: Optional[int]):
"""Calculate the reorg range"""
def diff_pos(hashes1, hashes2):
"""Returns the index of the first difference in the hash lists.
If both lists match returns their length."""
for n, (hash1, hash2) in enumerate(zip(hashes1, hashes2)):
if hash1 != hash2:
return n
return len(hashes)
if count is None:
# A real reorg
start = self.height - 1
count = 1
while start > 0:
hashes = await self.db.fs_block_hashes(start, count)
hex_hashes = [hash_to_hex_str(hash) for hash in hashes]
d_hex_hashes = await self.daemon.block_hex_hashes(start, count)
n = diff_pos(hex_hashes, d_hex_hashes)
if n > 0:
start += n
break
count = min(count * 2, start)
start -= count
count = (self.height - start) + 1
else:
start = (self.height - count) + 1
return start, count
def estimate_txs_remaining(self):
# Try to estimate how many txs there are to go
daemon_height = self.daemon.cached_height()
coin = self.coin
tail_count = daemon_height - max(self.height, coin.TX_COUNT_HEIGHT)
# Damp the initial enthusiasm
realism = max(2.0 - 0.9 * self.height / coin.TX_COUNT_HEIGHT, 1.0)
return (tail_count * coin.TX_PER_BLOCK +
max(coin.TX_COUNT - self.tx_count, 0)) * realism
# - Flushing
def flush_data(self):
"""The data for a flush. The lock must be taken."""
assert self.state_lock.locked()
return FlushData(self.height, self.tx_count, self.headers,
self.block_hashes, self.block_txs, self.undo_infos,
self.utxo_cache, self.db_deletes, self.tip)
async def flush(self, flush_utxos):
def flush():
self.db.flush_dbs(self.flush_data(), flush_utxos,
self.estimate_txs_remaining)
await self.run_in_thread_with_lock(flush)
async def _maybe_flush(self):
# If caught up, flush everything as client queries are
# performed on the DB.
if self._caught_up_event.is_set():
await self.flush(True)
elif time.perf_counter() > self.next_cache_check:
await self.flush(True)
self.next_cache_check = time.perf_counter() + 30
def check_cache_size(self):
"""Flush a cache if it gets too big."""
# Good average estimates based on traversal of subobjects and
# requesting size from Python (see deep_getsizeof).
one_MB = 1000 * 1000
utxo_cache_size = len(self.utxo_cache) * 205
db_deletes_size = len(self.db_deletes) * 57
hist_cache_size = self.db.history.unflushed_memsize()
# Roughly ntxs * 32 + nblocks * 42
tx_hash_size = ((self.tx_count - self.db.fs_tx_count) * 32 +
(self.height - self.db.fs_height) * 42)
utxo_MB = (db_deletes_size + utxo_cache_size) // one_MB
hist_MB = (hist_cache_size + tx_hash_size) // one_MB
self.logger.info('our height: {:,d} daemon: {:,d} '
'UTXOs {:,d}MB hist {:,d}MB'.format(
self.height, self.daemon.cached_height(), utxo_MB,
hist_MB))
# Flush history if it takes up over 20% of cache memory.
# Flush UTXOs once they take up 80% of cache memory.
cache_MB = self.env.cache_MB
if utxo_MB + hist_MB >= cache_MB or hist_MB >= cache_MB // 5:
return utxo_MB >= cache_MB * 4 // 5
return None
def advance_blocks(self, blocks):
"""Synchronously advance the blocks.
It is already verified they correctly connect onto our tip.
"""
min_height = self.db.min_undo_height(self.daemon.cached_height())
height = self.height
for block in blocks:
height += 1
undo_info = self.advance_txs(
height, block.transactions,
self.coin.electrum_header(block.header, height),
self.coin.header_hash(block.header))
if height >= min_height:
self.undo_infos.append((undo_info, height))
self.db.write_raw_block(block.raw, height)
headers = [block.header for block in blocks]
self.height = height
self.headers.extend(headers)
self.tip = self.coin.header_hash(headers[-1])
def advance_txs(self, height, txs, header, block_hash):
self.block_hashes.append(block_hash)
self.block_txs.append(
(b''.join(tx_hash
for tx, tx_hash in txs), [tx.raw for tx, _ in txs]))
undo_info = []
tx_num = self.tx_count
hashXs_by_tx = []
# Use local vars for speed in the loops
put_utxo = self.utxo_cache.__setitem__
spend_utxo = self.spend_utxo
undo_info_append = undo_info.append
update_touched = self.touched.update
append_hashX_by_tx = hashXs_by_tx.append
hashX_from_script = self.coin.hashX_from_script
for tx, tx_hash in txs:
hashXs = []
append_hashX = hashXs.append
tx_numb = pack('<I', tx_num)
# Spend the inputs
for txin in tx.inputs:
if txin.is_generation():
continue
cache_value = spend_utxo(txin.prev_hash, txin.prev_idx)
undo_info_append(cache_value)
append_hashX(cache_value[:-12])
# Add the new UTXOs
for idx, txout in enumerate(tx.outputs):
# Get the hashX. Ignore unspendable outputs
hashX = hashX_from_script(txout.pk_script)
if hashX:
append_hashX(hashX)
put_utxo(tx_hash + pack('<H', idx),
hashX + tx_numb + pack('<Q', txout.value))
append_hashX_by_tx(hashXs)
update_touched(hashXs)
self.db.total_transactions.append(tx_hash)
tx_num += 1
self.db.history.add_unflushed(hashXs_by_tx, self.tx_count)
self.tx_count = tx_num
self.db.tx_counts.append(tx_num)
return undo_info
def backup_blocks(self, raw_blocks):
"""Backup the raw blocks and flush.
The blocks should be in order of decreasing height, starting at.
self.height. A flush is performed once the blocks are backed up.
"""
self.db.assert_flushed(self.flush_data())
assert self.height >= len(raw_blocks)
coin = self.coin
for raw_block in raw_blocks:
self.logger.info("backup block %i", self.height)
# Check and update self.tip
block = coin.block(raw_block, self.height)
header_hash = coin.header_hash(block.header)
if header_hash != self.tip:
raise ChainError(
'backup block {} not tip {} at height {:,d}'.format(
hash_to_hex_str(header_hash),
hash_to_hex_str(self.tip), self.height))
self.tip = coin.header_prevhash(block.header)
self.backup_txs(block.transactions)
self.height -= 1
self.db.tx_counts.pop()
self.logger.info(f'backed up to height {self.height:,d}')
def backup_txs(self, txs):
# Prevout values, in order down the block (coinbase first if present)
# undo_info is in reverse block order
undo_info = self.db.read_undo_info(self.height)
if undo_info is None:
raise ChainError(
f'no undo information found for height {self.height:,d}')
n = len(undo_info)
# Use local vars for speed in the loops
s_pack = pack
undo_entry_len = 12 + HASHX_LEN
for tx, tx_hash in reversed(txs):
for idx, txout in enumerate(tx.outputs):
# Spend the TX outputs. Be careful with unspendable
# outputs - we didn't save those in the first place.
hashX = self.coin.hashX_from_script(txout.pk_script)
if hashX:
cache_value = self.spend_utxo(tx_hash, idx)
self.touched.add(cache_value[:-12])
# Restore the inputs
for txin in reversed(tx.inputs):
if txin.is_generation():
continue
n -= undo_entry_len
undo_item = undo_info[n:n + undo_entry_len]
self.utxo_cache[txin.prev_hash +
s_pack('<H', txin.prev_idx)] = undo_item
self.touched.add(undo_item[:-12])
self.db.total_transactions.pop()
assert n == 0
self.tx_count -= len(txs)
"""An in-memory UTXO cache, representing all changes to UTXO state
since the last DB flush.
We want to store millions of these in memory for optimal
performance during initial sync, because then it is possible to
spend UTXOs without ever going to the database (other than as an
entry in the address history, and there is only one such entry per
TX not per UTXO). So store them in a Python dictionary with
binary keys and values.
Key: TX_HASH + TX_IDX (32 + 2 = 34 bytes)
Value: HASHX + TX_NUM + VALUE (11 + 4 + 8 = 23 bytes)
That's 57 bytes of raw data in-memory. Python dictionary overhead
means each entry actually uses about 205 bytes of memory. So
almost 5 million UTXOs can fit in 1GB of RAM. There are
approximately 42 million UTXOs on bitcoin mainnet at height
433,000.
Semantics:
add: Add it to the cache dictionary.
spend: Remove it if in the cache dictionary. Otherwise it's
been flushed to the DB. Each UTXO is responsible for two
entries in the DB. Mark them for deletion in the next
cache flush.
The UTXO database format has to be able to do two things efficiently:
1. Given an address be able to list its UTXOs and their values
so its balance can be efficiently computed.
2. When processing transactions, for each prevout spent - a (tx_hash,
idx) pair - we have to be able to remove it from the DB. To send
notifications to clients we also need to know any address it paid
to.
To this end we maintain two "tables", one for each point above:
1. Key: b'u' + address_hashX + tx_idx + tx_num
Value: the UTXO value as a 64-bit unsigned integer
2. Key: b'h' + compressed_tx_hash + tx_idx + tx_num
Value: hashX
The compressed tx hash is just the first few bytes of the hash of
the tx in which the UTXO was created. As this is not unique there
will be potential collisions so tx_num is also in the key. When
looking up a UTXO the prefix space of the compressed hash needs to
be searched and resolved if necessary with the tx_num. The
collision rate is low (<0.1%).
"""
def spend_utxo(self, tx_hash, tx_idx):
"""Spend a UTXO and return the 33-byte value.
If the UTXO is not in the cache it must be on disk. We store
all UTXOs so not finding one indicates a logic error or DB
corruption.
"""
# Fast track is it being in the cache
idx_packed = pack('<H', tx_idx)
cache_value = self.utxo_cache.pop(tx_hash + idx_packed, None)
if cache_value:
return cache_value
# Spend it from the DB.
# Key: b'h' + compressed_tx_hash + tx_idx + tx_num
# Value: hashX
prefix = b'h' + tx_hash[:4] + idx_packed
candidates = {
db_key: hashX
for db_key, hashX in self.db.utxo_db.iterator(prefix=prefix)
}
for hdb_key, hashX in candidates.items():
tx_num_packed = hdb_key[-4:]
if len(candidates) > 1:
tx_num, = unpack('<I', tx_num_packed)
try:
hash, height = self.db.fs_tx_hash(tx_num)
except IndexError:
self.logger.error(
"data integrity error for hashx history: %s missing tx #%s (%s:%s)",
hashX.hex(), tx_num, hash_to_hex_str(tx_hash), tx_idx)
continue
if hash != tx_hash:
assert hash is not None # Should always be found
continue
# Key: b'u' + address_hashX + tx_idx + tx_num
# Value: the UTXO value as a 64-bit unsigned integer
udb_key = b'u' + hashX + hdb_key[-6:]
utxo_value_packed = self.db.utxo_db.get(udb_key)
if utxo_value_packed is None:
self.logger.warning("%s:%s is not found in UTXO db for %s",
hash_to_hex_str(tx_hash), tx_idx,
hash_to_hex_str(hashX))
raise ChainError(
f"{hash_to_hex_str(tx_hash)}:{tx_idx} is not found in UTXO db for {hash_to_hex_str(hashX)}"
)
# Remove both entries for this UTXO
self.db_deletes.append(hdb_key)
self.db_deletes.append(udb_key)
return hashX + tx_num_packed + utxo_value_packed
self.logger.error(
'UTXO {hash_to_hex_str(tx_hash)} / {tx_idx} not found in "h" table'
)
raise ChainError('UTXO {} / {:,d} not found in "h" table'.format(
hash_to_hex_str(tx_hash), tx_idx))
async def _process_prefetched_blocks(self):
"""Loop forever processing blocks as they arrive."""
while True:
if self.height == self.daemon.cached_height():
if not self._caught_up_event.is_set():
await self._first_caught_up()
self._caught_up_event.set()
await self.blocks_event.wait()
self.blocks_event.clear()
if self.reorg_count: # this could only happen by calling the reorg rpc
await self.reorg_chain(self.reorg_count)
self.reorg_count = 0
else:
blocks = self.prefetcher.get_prefetched_blocks()
try:
await self.check_and_advance_blocks(blocks)
except Exception:
self.logger.exception("error while processing txs")
raise
async def _first_caught_up(self):
self.logger.info(f'caught up to height {self.height}')
# Flush everything but with first_sync->False state.
first_sync = self.db.first_sync
self.db.first_sync = False
await self.flush(True)
if first_sync:
self.logger.info(f'{lbry.__version__} synced to '
f'height {self.height:,d}')
# Reopen for serving
await self.db.open_for_serving()
async def _first_open_dbs(self):
await self.db.open_for_sync()
self.height = self.db.db_height
self.tip = self.db.db_tip
self.tx_count = self.db.db_tx_count
# --- External API
async def fetch_and_process_blocks(self, caught_up_event):
"""Fetch, process and index blocks from the daemon.
Sets caught_up_event when first caught up. Flushes to disk
and shuts down cleanly if cancelled.
This is mainly because if, during initial sync ElectrumX is
asked to shut down when a large number of blocks have been
processed but not written to disk, it should write those to
disk before exiting, as otherwise a significant amount of work
could be lost.
"""
self._caught_up_event = caught_up_event
try:
await self._first_open_dbs()
self.status_server.set_height(self.db.fs_height, self.db.db_tip)
await asyncio.wait([
self.prefetcher.main_loop(self.height),
self._process_prefetched_blocks()
])
except asyncio.CancelledError:
raise
except:
self.logger.exception("Block processing failed!")
raise
finally:
self.status_server.stop()
# Shut down block processing
self.logger.info('flushing to DB for a clean shutdown...')
await self.flush(True)
self.db.close()
self.executor.shutdown(wait=True)
def force_chain_reorg(self, count):
"""Force a reorg of the given number of blocks.
Returns True if a reorg is queued, false if not caught up.
"""
if self._caught_up_event.is_set():
self.reorg_count = count
self.blocks_event.set()
return True
return False
async def _make_udp_server(self, port):
s = StatusServer()
await s.start(0, b'\x00' * 32, '127.0.0.1', port)
self.addCleanup(s.stop)