bitcoin/test/functional/dbcrash.py

#!/usr/bin/env python3
# Copyright (c) 2017 The Bitcoin Core developers
# Distributed under the MIT software license, see the accompanying
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
"""Test recovery from a crash during chainstate writing."""

from test_framework.test_framework import BitcoinTestFramework
from test_framework.util import *
from test_framework.script import *
from test_framework.mininode import *
import random
try:
    import http.client as httplib
except ImportError:
    import httplib
import errno

'''
Test structure:

- 4 nodes
  * node0, node1, and node2 will have different dbcrash ratios, and different
    dbcache sizes
  * node3 will be a regular node, with no crashing.
  * The nodes will not connect to each other.

- use default test framework starting chain. initialize starting_tip_height to
  tip height.

- Main loop:
  * generate lots of transactions on node3, enough to fill up a block.
  * uniformly randomly pick a tip height from starting_tip_height to
    tip_height; with probability 1/(height_difference+4), invalidate this block.
  * mine enough blocks to overtake tip_height at start of loop.
  * for each node in [node0,node1,node2]:
     - for each mined block:
       * submit block to node
       * if node crashed on/after submitting:
         - restart until recovery succeeds
         - check that utxo matches node3 using gettxoutsetinfo
'''

class ChainstateWriteCrashTest(BitcoinTestFramework):

    def __init__(self):
        super().__init__()
        self.num_nodes = 4
        self.setup_clean_chain = False

        # Set -maxmempool=0 to turn off mempool memory sharing with dbcache
        # Set -rpcservertimeout=900 to reduce socket disconnects in this
        # long-running test
        self.base_args = ["-limitdescendantsize=0", "-maxmempool=0", "-rpcservertimeout=900"]

        # Set different crash ratios and cache sizes.  Note that not all of
        # -dbcache goes to pcoinsTip.
        self.node0_args = ["-dbcrashratio=8", "-dbcache=4", "-dbbatchsize=200000"] + self.base_args
        self.node1_args = ["-dbcrashratio=16", "-dbcache=8", "-dbbatchsize=200000"] + self.base_args
        self.node2_args = ["-dbcrashratio=24", "-dbcache=16", "-dbbatchsize=200000"] + self.base_args

        # Node3 is a normal node with default args, except will mine full blocks
        self.node3_args = ["-blockmaxweight=4000000"]
        self.extra_args = [self.node0_args, self.node1_args, self.node2_args, self.node3_args]

        # We'll track some test coverage statistics
        self.restart_counts = [0, 0, 0] # Track the restarts for nodes 0-2
        self.crashed_on_restart = 0     # Track count of crashes during recovery

    def setup_network(self):
        self.setup_nodes()
        # Leave them unconnected, we'll use submitblock directly in this test

    # Starts up a given node id, waits for the tip to reach the given block
    # hash, and calculates the utxo hash.  Exceptions on startup should
    # indicate node crash (due to -dbcrashratio), in which case we try again.
    # Give up after 60 seconds.
    # Returns the utxo hash of the given node.
    def restart_node(self, node_index, expected_tip):
        time_start = time.time()
        while time.time() - time_start < 60:
            try:
                # Any of these RPC calls could throw due to node crash
                self.nodes[node_index] = self.start_node(node_index, self.options.tmpdir, self.extra_args[node_index])
                self.nodes[node_index].waitforblock(expected_tip)
                utxo_hash = self.nodes[node_index].gettxoutsetinfo()['hash_serialized_2']
                return utxo_hash
            except:
                # An exception here should mean the node is about to crash.
                # If bitcoind exits, then try again.  wait_for_node_exit()
                # should raise an exception if bitcoind doesn't exit.
                wait_for_node_exit(node_index, timeout=10)
            self.crashed_on_restart += 1
            time.sleep(1)

        # If we got here, bitcoind isn't coming back up on restart.  Could be a
        # bug in bitcoind, or we've gotten unlucky with our dbcrash ratio --
        # perhaps we generated a test case that blew up our cache?
        # TODO: If this happens a lot, we should try to restart without -dbcrashratio
        # and make sure that recovery happens.
        raise AssertionError("Unable to successfully restart node %d in allotted time", node_index)

    # Try submitting a block to the given node.
    # Catch any exceptions that indicate the node has crashed.
    # Returns true if the block was submitted successfully; false otherwise.
    def submit_block_catch_error(self, node_index, block):
        try:
            self.nodes[node_index].submitblock(block)
            return True
        except (httplib.CannotSendRequest, httplib.RemoteDisconnected) as e:
            self.log.debug("node %d submitblock raised exception: %s", node_index, e)
            return False
        except OSError as e:
            self.log.debug("node %d submitblock raised OSError exception: errno=%s", node_index, e.errno)
            if e.errno in [errno.EPIPE, errno.ECONNREFUSED, errno.ECONNRESET]:
                # The node has likely crashed
                return False
            else:
                # Unexpected exception, raise
                raise

    # Use submitblock to sync node3's chain with the other nodes
    # If submitblock fails, restart the node and get the new utxo hash.
    def sync_node3blocks(self, block_hashes):
        # If any nodes crash while updating, we'll compare utxo hashes to
        # ensure recovery was successful.
        node3_utxo_hash = self.nodes[3].gettxoutsetinfo()['hash_serialized_2']

        # Retrieve all the blocks from node3
        blocks = []
        for block_hash in block_hashes:
            blocks.append([block_hash, self.nodes[3].getblock(block_hash, 0)])

        # Deliver each block to each other node
        for i in range(3):
            nodei_utxo_hash = None
            self.log.debug("Syncing blocks to node %d", i)
            for (block_hash, block) in blocks:
                # Get the block from node3, and submit to node_i
                self.log.debug("submitting block %s", block_hash)
                if not self.submit_block_catch_error(i, block):
                    # TODO: more carefully check that the crash is due to -dbcrashratio
                    # (change the exit code perhaps, and check that here?)
                    wait_for_node_exit(i, timeout=30)
                    self.log.debug("Restarting node %d after block hash %s", i, block_hash)
                    nodei_utxo_hash = self.restart_node(i, block_hash)
                    assert nodei_utxo_hash is not None
                    self.restart_counts[i] += 1
                else:
                    # Clear it out after successful submitblock calls -- the cached
                    # utxo hash will no longer be correct
                    nodei_utxo_hash = None

            # Check that the utxo hash matches node3's utxo set
            # NOTE: we only check the utxo set if we had to restart the node
            # after the last block submitted:
            # - checking the utxo hash causes a cache flush, which we don't
            # want to do every time; so
            # - we only update the utxo cache after a node restart, since flushing
            # the cache is a no-op at that point
            if nodei_utxo_hash is not None:
                self.log.debug("Checking txoutsetinfo matches for node %d", i)
                assert_equal(nodei_utxo_hash, node3_utxo_hash)

    # Verify that the utxo hash of each node matches node3.
    # Restart any nodes that crash while querying.
    def verify_utxo_hash(self):
        node3_utxo_hash = self.nodes[3].gettxoutsetinfo()['hash_serialized_2']
        self.log.info("Verifying utxo hash matches for all nodes")

        for i in range(3):
            try:
                nodei_utxo_hash = self.nodes[i].gettxoutsetinfo()['hash_serialized_2']
            except OSError:
                # probably a crash on db flushing
                nodei_utxo_hash = self.restart_node(i, self.nodes[3].getbestblockhash())
            assert_equal(nodei_utxo_hash, node3_utxo_hash)


    def generate_small_transactions(self, node, count, utxo_list):
        FEE = 1000 # TODO: replace this with node relay fee based calculation
        num_transactions = 0
        random.shuffle(utxo_list)
        while len(utxo_list) >= 2 and num_transactions < count:
            tx = CTransaction()
            input_amount = 0
            for i in range(2):
                utxo = utxo_list.pop()
                tx.vin.append(CTxIn(COutPoint(int(utxo['txid'], 16), utxo['vout'])))
                input_amount += int(utxo['amount']*COIN)
            output_amount = (input_amount - FEE)//3

            if output_amount <= 0:
                # Sanity check -- if we chose inputs that are too small, skip
                continue

            for i in range(3):
                tx.vout.append(CTxOut(output_amount, hex_str_to_bytes(utxo['scriptPubKey'])))

            # Sign and send the transaction to get into the mempool
            tx_signed_hex = node.signrawtransaction(ToHex(tx))['hex']
            node.sendrawtransaction(tx_signed_hex)
            num_transactions += 1

    def run_test(self):

        # Start by creating a lot of utxos on node3
        initial_height = self.nodes[3].getblockcount()
        utxo_list = create_confirmed_utxos(self.nodes[3].getnetworkinfo()['relayfee'], self.nodes[3], 5000)
        self.log.info("Prepped %d utxo entries", len(utxo_list))

        # Sync these blocks with the other nodes
        block_hashes_to_sync = []
        for height in range(initial_height+1, self.nodes[3].getblockcount()+1):
            block_hashes_to_sync.append(self.nodes[3].getblockhash(height))

        self.log.debug("Syncing %d blocks with other nodes", len(block_hashes_to_sync))
        # Syncing the blocks could cause nodes to crash, so the test begins here.
        self.sync_node3blocks(block_hashes_to_sync)

        starting_tip_height = self.nodes[3].getblockcount()

        # Main test loop:
        # each time through the loop, generate a bunch of transactions,
        # and then either mine a single new block on the tip, or some-sized reorg.
        for i in range(40):
            self.log.info("Iteration %d, generating 2500 transactions %s", i, self.restart_counts)
            # Generate a bunch of small-ish transactions
            self.generate_small_transactions(self.nodes[3], 2500, utxo_list)
            # Pick a random block between current tip, and starting tip
            current_height = self.nodes[3].getblockcount()
            random_height = random.randint(starting_tip_height, current_height)
            self.log.debug("At height %d, considering height %d", current_height, random_height)
            if random_height > starting_tip_height:
                # Randomly reorg from this point with some probability (1/4 for
                # tip, 1/5 for tip-1, ...)
                if random.random() < 1.0/(current_height + 4 - random_height):
                    self.log.debug("Invalidating block at height %d", random_height)
                    self.nodes[3].invalidateblock(self.nodes[3].getblockhash(random_height))

            # Now generate new blocks until we pass the old tip height
            self.log.debug("Mining longer tip")
            block_hashes = self.nodes[3].generate(current_height+1-self.nodes[3].getblockcount())
            self.log.debug("Syncing %d new blocks...", len(block_hashes))
            self.sync_node3blocks(block_hashes)
            utxo_list = self.nodes[3].listunspent()
            self.log.debug("Node3 utxo count: %d", len(utxo_list))

        # Check that the utxo hashes agree with node3
        # Useful side effect: each utxo cache gets flushed here, so that we
        # won't get crashes on shutdown at the end of the test.
        self.verify_utxo_hash()

        # Check the test coverage
        self.log.info("Restarted nodes: %s; crashes on restart: %d", self.restart_counts, self.crashed_on_restart)

        # If no nodes were restarted, we didn't test anything.
        assert self.restart_counts != [0, 0, 0]

        # Make sure we tested the case of crash-during-recovery.
        assert self.crashed_on_restart > 0

        # Warn if any of the nodes escaped restart.
        for i in range(3):
            if self.restart_counts[i] == 0:
                self.log.warn("Node %d never crashed during utxo flush!", i)

if __name__ == "__main__":
    ChainstateWriteCrashTest().main()