1 // Copyright (c) 2023 The Limenka 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 LIMENKA_KERNEL_DISCONNECTED_TRANSACTIONS_H
6 #define LIMENKA_KERNEL_DISCONNECTED_TRANSACTIONS_H
7 8 #include <primitives/transaction.h>
9 #include <util/hasher.h>
10 11 #include <list>
12 #include <unordered_map>
13 #include <vector>
14 15 /** Maximum bytes for transactions to store for processing during reorg */
16 static const unsigned int MAX_DISCONNECTED_TX_POOL_BYTES{20'000'000};
17 /**
18 * DisconnectedBlockTransactions
19 20 * During the reorg, it's desirable to re-add previously confirmed transactions
21 * to the mempool, so that anything not re-confirmed in the new chain is
22 * available to be mined. However, it's more efficient to wait until the reorg
23 * is complete and process all still-unconfirmed transactions at that time,
24 * since we expect most confirmed transactions to (typically) still be
25 * confirmed in the new chain, and re-accepting to the memory pool is expensive
26 * (and therefore better to not do in the middle of reorg-processing).
27 * Instead, store the disconnected transactions (in order!) as we go, remove any
28 * that are included in blocks in the new chain, and then process the remaining
29 * still-unconfirmed transactions at the end.
30 *
31 * Order of queuedTx:
32 * The front of the list should be the most recently-confirmed transactions (transactions at the
33 * end of vtx of blocks closer to the tip). If memory usage grows too large, we trim from the front
34 * of the list. After trimming, transactions can be re-added to the mempool from the back of the
35 * list to the front without running into missing inputs.
36 */
37 class DisconnectedBlockTransactions {
38 private:
39 /** Cached dynamic memory usage for the `CTransactionRef`s */
40 uint64_t cachedInnerUsage = 0;
41 const size_t m_max_mem_usage;
42 std::list<CTransactionRef> queuedTx;
43 using TxList = decltype(queuedTx);
44 std::unordered_map<uint256, TxList::iterator, SaltedTxidHasher> iters_by_txid;
45 46 /** Trim the earliest-added entries until we are within memory bounds. */
47 std::vector<CTransactionRef> LimitMemoryUsage();
48 49 public:
50 DisconnectedBlockTransactions(size_t max_mem_usage)
51 : m_max_mem_usage{max_mem_usage} {}
52 53 ~DisconnectedBlockTransactions();
54 55 size_t DynamicMemoryUsage() const;
56 57 /** Add transactions from the block, iterating through vtx in reverse order. Callers should call
58 * this function for blocks in descending order by block height.
59 * We assume that callers never pass multiple transactions with the same txid, otherwise things
60 * can go very wrong in removeForBlock due to queuedTx containing an item without a
61 * corresponding entry in iters_by_txid.
62 * @returns vector of transactions that were evicted for size-limiting.
63 */
64 [[nodiscard]] std::vector<CTransactionRef> AddTransactionsFromBlock(const std::vector<CTransactionRef>& vtx);
65 66 /** Remove any entries that are in this block. */
67 void removeForBlock(const std::vector<CTransactionRef>& vtx);
68 69 size_t size() const { return queuedTx.size(); }
70 71 void clear();
72 73 /** Clear all data structures and return the list of transactions. */
74 std::list<CTransactionRef> take();
75 };
76 #endif // LIMENKA_KERNEL_DISCONNECTED_TRANSACTIONS_H
77