text: #!/usr/bin/env python3
  # Copyright (c) 2017-2019 The bitmonkey 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.
  
  - 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"""
  
  import errno
  import http.client
  import random
  import time
  
  from test_framework.messages import COIN, COutPoint, CTransaction, CTxIn, CTxOut, ToHex
  from test_framework.test_framework import bitmonkeyTestFramework
  from test_framework.util import assert_equal, create_confirmed_utxos, hex_str_to_bytes
  
  
  class ChainstateWriteCrashTest(bitmonkeyTestFramework):
      def set_test_params(self):
          self.num_nodes = 4
          self.setup_clean_chain = False
          # Need a bit of extra time for the nodes to start up for this test
          self.rpc_timeout = 90
  
          # 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", "-dbbatchsize=200000"]
  
          # Set different crash ratios and cache sizes.  Note that not all of
          # -dbcache goes to pcoinsTip.
          self.node0_args = ["-dbcrashratio=8", "-dbcache=4"] + self.base_args
          self.node1_args = ["-dbcrashratio=16", "-dbcache=8"] + self.base_args
          self.node2_args = ["-dbcrashratio=24", "-dbcache=16"] + 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]
  
      def skip_test_if_missing_module(self):
          self.skip_if_no_wallet()
  
      def setup_network(self):
          self.add_nodes(self.num_nodes, extra_args=self.extra_args)
          self.start_nodes()
          self.import_deterministic_coinbase_privkeys()
          # Leave them unconnected, we'll use submitblock directly in this test
  
      def restart_node(self, node_index, expected_tip):
          """Start up a given node id, wait for the tip to reach the given block hash, and calculate 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."""
  
          time_start = time.time()
          while time.time() - time_start < 120:
              try:
                  # Any of these RPC calls could throw due to node crash
                  self.start_node(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 bitmonkeyd exits, then try again.  wait_for_node_exit()
                  # should raise an exception if bitmonkeyd doesn't exit.
                  self.wait_for_node_exit(node_index, timeout=10)
              self.crashed_on_restart += 1
              time.sleep(1)
  
          # If we got here, bitmonkeyd isn't coming back up on restart.  Could be a
          # bug in bitmonkeyd, 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)
  
      def submit_block_catch_error(self, node_index, block):
          """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."""
  
          try:
              self.nodes[node_index].submitblock(block)
              return True
          except (http.client.CannotSendRequest, http.client.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
  
      def sync_node3blocks(self, block_hashes):
          """Use submitblock to sync node3's chain with the other nodes
  
          If submitblock fails, restart the node and get the new utxo hash.
          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?)
                      self.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)
  
      def verify_utxo_hash(self):
          """Verify that the utxo hash of each node matches node3.
  
          Restart any nodes that crash while querying."""
          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.signrawtransactionwithwallet(ToHex(tx))['hex']
              node.sendrawtransaction(tx_signed_hex)
              num_transactions += 1
  
      def run_test(self):
          # Track 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
  
          # 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 = []
              while current_height + 1 > self.nodes[3].getblockcount():
                  block_hashes.extend(self.nodes[3].generate(min(10, 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()
  