1 // Copyright (c) 2023-present The Bitcoin Core developers
2 // Distributed under the MIT software license, see the accompanying
3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
4 5 #ifndef BITCOIN_KERNEL_DISCONNECTED_TRANSACTIONS_H
6 #define BITCOIN_KERNEL_DISCONNECTED_TRANSACTIONS_H
7 8 #include <primitives/transaction.h>
9 #include <util/hasher.h>
10 11 #include <cstddef>
12 #include <cstdint>
13 #include <list>
14 #include <unordered_map>
15 #include <vector>
16 17 /** Maximum bytes for transactions to store for processing during reorg */
18 static const unsigned int MAX_DISCONNECTED_TX_POOL_BYTES{20'000'000};
19 /**
20 * DisconnectedBlockTransactions
21 22 * During the reorg, it's desirable to re-add previously confirmed transactions
23 * to the mempool, so that anything not re-confirmed in the new chain is
24 * available to be mined. However, it's more efficient to wait until the reorg
25 * is complete and process all still-unconfirmed transactions at that time,
26 * since we expect most confirmed transactions to (typically) still be
27 * confirmed in the new chain, and re-accepting to the memory pool is expensive
28 * (and therefore better to not do in the middle of reorg-processing).
29 * Instead, store the disconnected transactions (in order!) as we go, remove any
30 * that are included in blocks in the new chain, and then process the remaining
31 * still-unconfirmed transactions at the end.
32 *
33 * Order of queuedTx:
34 * The front of the list should be the most recently-confirmed transactions (transactions at the
35 * end of vtx of blocks closer to the tip). If memory usage grows too large, we trim from the front
36 * of the list. After trimming, transactions can be re-added to the mempool from the back of the
37 * list to the front without running into missing inputs.
38 */
39 class DisconnectedBlockTransactions {
40 private:
41 /** Cached dynamic memory usage for the `CTransactionRef`s */
42 uint64_t cachedInnerUsage = 0;
43 const size_t m_max_mem_usage;
44 std::list<CTransactionRef> queuedTx;
45 using TxList = decltype(queuedTx);
46 std::unordered_map<Txid, TxList::iterator, SaltedTxidHasher> iters_by_txid;
47 48 /** Trim the earliest-added entries until we are within memory bounds. */
49 std::vector<CTransactionRef> LimitMemoryUsage();
50 51 public:
52 DisconnectedBlockTransactions(size_t max_mem_usage)
53 : m_max_mem_usage{max_mem_usage} {}
54 55 ~DisconnectedBlockTransactions();
56 57 size_t DynamicMemoryUsage() const;
58 59 /** Add transactions from the block, iterating through vtx in reverse order. Callers should call
60 * this function for blocks in descending order by block height.
61 * We assume that callers never pass multiple transactions with the same txid, otherwise things
62 * can go very wrong in removeForBlock due to queuedTx containing an item without a
63 * corresponding entry in iters_by_txid.
64 * @returns vector of transactions that were evicted for size-limiting.
65 */
66 [[nodiscard]] std::vector<CTransactionRef> AddTransactionsFromBlock(const std::vector<CTransactionRef>& vtx);
67 68 /** Remove any entries that are in this block. */
69 void removeForBlock(const std::vector<CTransactionRef>& vtx);
70 71 size_t size() const { return queuedTx.size(); }
72 73 void clear();
74 75 /** Clear all data structures and return the list of transactions. */
76 std::list<CTransactionRef> take();
77 };
78 #endif // BITCOIN_KERNEL_DISCONNECTED_TRANSACTIONS_H
79