Repository: bitcoin/bitcoin
File: test/functional/feature_assumeutxo.py (Python)

Code before:
        # Sync-up headers chain on snapshot_node to load snapshot
        headers_provider_conn = snapshot_node.add_p2p_connection(P2PInterface())
        headers_provider_conn.wait_for_getheaders()
        msg = msg_headers()
        for block_num in range(1, miner.getblockcount()+1):
            msg.headers.append(from_hex(CBlockHeader(), miner.getblockheader(miner.getblockhash(block_num), verbose=False)))
        headers_provider_conn.send_message(msg)

        # Ensure headers arrived
        default_value = {'status': ''}  # No status
        headers_tip_hash = miner.getbestblockhash()
        self.wait_until(lambda: next(filter(lambda x: x['hash'] == headers_tip_hash, snapshot_node.getchaintips()), default_value)['status'] == "headers-only")
        snapshot_node.disconnect_p2ps()

        # Load snapshot
        snapshot_node.loadtxoutset(snapshot['path'])

        # Connect nodes and verify the ibd_node can sync-up the headers-chain from the snapshot_node
        self.connect_nodes(ibd_node.index, snapshot_node.index)
        snapshot_block_hash = snapshot['base_hash']
        self.wait_until(lambda: next(filter(lambda x: x['hash'] == snapshot_block_hash, ibd_node.getchaintips()), default_value)['status'] == "headers-only")

        # Once the headers-chain is synced, the ibd_node must avoid requesting historical blocks from the snapshot_node.
        # If it does request such blocks, the snapshot_node will ignore requests it cannot fulfill, causing the ibd_node
        # to stall. This stall could last for up to 10 min, ultimately resulting in an abrupt disconnection due to the
        # ibd_node's perceived unresponsiveness.
        time.sleep(3)  # Sleep here because we can't detect when a node avoids requesting blocks from other peer.
        assert_equal(len(ibd_node.getpeerinfo()[0]['inflight']), 0)

        # Now disconnect nodes and finish background chain sync
        self.disconnect_nodes(ibd_node.index, snapshot_node.index)
        self.connect_nodes(snapshot_node.index, miner.index)
        self.sync_blocks(nodes=(miner, snapshot_node))
        # Check the base snapshot block was stored and ensure node signals full-node service support
        self.wait_until(lambda: not try_rpc(-1, "Block not available (not fully downloaded)", snapshot_node.getblock, snapshot_block_hash))
        self.wait_until(lambda: 'NETWORK' in snapshot_node.getnetworkinfo()['localservicesnames'])

        # Now that the snapshot_node is synced, verify the ibd_node can sync from it
        self.connect_nodes(snapshot_node.index, ibd_node.index)
        assert 'NETWORK' in ibd_node.getpeerinfo()[0]['servicesnames']
        self.sync_blocks(nodes=(ibd_node, snapshot_node))

    def assert_only_network_limited_service(self, node):
        node_services = node.getnetworkinfo()['localservicesnames']
        assert 'NETWORK' not in node_services
        assert 'NETWORK_LIMITED' in node_services

    def run_test(self):
        """
        Bring up two (disconnected) nodes, mine some new blocks on the first,
        and generate a UTXO snapshot.

Review comment (suggestion):
For clarity/readability, suggest using a named argument in the `ensure` invocations where you pass a timeout value (edit: maybe enforce that with a `*` parameter)

Code after:
        # Sync-up headers chain on snapshot_node to load snapshot
        headers_provider_conn = snapshot_node.add_p2p_connection(P2PInterface())
        headers_provider_conn.wait_for_getheaders()
        msg = msg_headers()
        for block_num in range(1, miner.getblockcount()+1):
            msg.headers.append(from_hex(CBlockHeader(), miner.getblockheader(miner.getblockhash(block_num), verbose=False)))
        headers_provider_conn.send_message(msg)

        # Ensure headers arrived
        default_value = {'status': ''}  # No status
        headers_tip_hash = miner.getbestblockhash()
        self.wait_until(lambda: next(filter(lambda x: x['hash'] == headers_tip_hash, snapshot_node.getchaintips()), default_value)['status'] == "headers-only")
        snapshot_node.disconnect_p2ps()

        # Load snapshot
        snapshot_node.loadtxoutset(snapshot['path'])

        # Connect nodes and verify the ibd_node can sync-up the headers-chain from the snapshot_node
        self.connect_nodes(ibd_node.index, snapshot_node.index)
        snapshot_block_hash = snapshot['base_hash']
        self.wait_until(lambda: next(filter(lambda x: x['hash'] == snapshot_block_hash, ibd_node.getchaintips()), default_value)['status'] == "headers-only")

        # Once the headers-chain is synced, the ibd_node must avoid requesting historical blocks from the snapshot_node.
        # If it does request such blocks, the snapshot_node will ignore requests it cannot fulfill, causing the ibd_node
        # to stall. This stall could last for up to 10 min, ultimately resulting in an abrupt disconnection due to the
        # ibd_node's perceived unresponsiveness.
        ensure_for(duration=3, f=lambda: len(ibd_node.getpeerinfo()[0]['inflight']) == 0)

        # Now disconnect nodes and finish background chain sync
        self.disconnect_nodes(ibd_node.index, snapshot_node.index)
        self.connect_nodes(snapshot_node.index, miner.index)
        self.sync_blocks(nodes=(miner, snapshot_node))
        # Check the base snapshot block was stored and ensure node signals full-node service support
        self.wait_until(lambda: not try_rpc(-1, "Block not found", snapshot_node.getblock, snapshot_block_hash))
        assert 'NETWORK' in snapshot_node.getnetworkinfo()['localservicesnames']

        # Now the snapshot_node is sync, verify the ibd_node can sync from it
        self.connect_nodes(snapshot_node.index, ibd_node.index)
        assert 'NETWORK' in ibd_node.getpeerinfo()[0]['servicesnames']
        self.sync_blocks(nodes=(ibd_node, snapshot_node))

    def assert_only_network_limited_service(self, node):
        node_services = node.getnetworkinfo()['localservicesnames']
        assert 'NETWORK' not in node_services
        assert 'NETWORK_LIMITED' in node_services

    def run_test(self):
        """
        Bring up two (disconnected) nodes, mine some new blocks on the first,
        and generate a UTXO snapshot.