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1 : : // Copyright (c) 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 : : #include <compare>
6 : : #include <stdint.h>
7 : : #include <memory>
8 : : #include <vector>
9 : :
10 : : #include <util/feefrac.h>
11 : :
12 : : #ifndef BITCOIN_TXGRAPH_H
13 : : #define BITCOIN_TXGRAPH_H
14 : :
15 : : static constexpr unsigned MAX_CLUSTER_COUNT_LIMIT{64};
16 : :
17 : : /** Data structure to encapsulate fees, sizes, and dependencies for a set of transactions.
18 : : *
19 : : * Each TxGraph represents one or two such graphs ("main", and optionally "staging"), to allow for
20 : : * working with batches of changes that may still be discarded.
21 : : *
22 : : * The connected components within each transaction graph are called clusters: whenever one
23 : : * transaction is reachable from another, through any sequence of is-parent-of or is-child-of
24 : : * relations, they belong to the same cluster (so clusters include parents, children, but also
25 : : * grandparents, siblings, cousins twice removed, ...).
26 : : *
27 : : * For each graph, TxGraph implicitly defines an associated total ordering on its transactions
28 : : * (its linearization) that respects topology (parents go before their children), aiming for it to
29 : : * be close to the optimal order those transactions should be mined in if the goal is fee
30 : : * maximization, though this is a best effort only, not a strong guarantee.
31 : : *
32 : : * For more explanation, see https://delvingbitcoin.org/t/introduction-to-cluster-linearization/1032
33 : : *
34 : : * This linearization is partitioned into chunks: groups of transactions that according to this
35 : : * order would be mined together. Each chunk consists of the highest-feerate prefix of what remains
36 : : * of the linearization after removing previous chunks. TxGraph guarantees that the maintained
37 : : * linearization always results in chunks consisting of transactions that are connected. A chunk's
38 : : * transactions always belong to the same cluster.
39 : : *
40 : : * The interface is designed to accommodate an implementation that only stores the transitive
41 : : * closure of dependencies, so if B spends C, it does not distinguish between "A spending B" and
42 : : * "A spending both B and C".
43 : : */
44 : 0 : class TxGraph
45 : : {
46 : : public:
47 : : /** Internal identifier for a transaction within a TxGraph. */
48 : : using GraphIndex = uint32_t;
49 : :
50 : : /** Data type used to reference transactions within a TxGraph.
51 : : *
52 : : * Every transaction within a TxGraph has exactly one corresponding TxGraph::Ref, held by users
53 : : * of the class. Destroying the TxGraph::Ref removes the corresponding transaction (in both the
54 : : * main and staging graphs).
55 : : *
56 : : * Users of the class can inherit from TxGraph::Ref. If all Refs are inherited this way, the
57 : : * Ref* pointers returned by TxGraph functions can be cast to, and used as, this inherited type.
58 : : */
59 : : class Ref;
60 : :
61 : : /** Virtual destructor, so inheriting is safe. */
62 : 0 : virtual ~TxGraph() = default;
63 : : /** Construct a new transaction with the specified feerate, and return a Ref to it.
64 : : * If a staging graph exists, the new transaction is only created there. In all
65 : : * further calls, only Refs created by AddTransaction() are allowed to be passed to this
66 : : * TxGraph object (or empty Ref objects). Ref objects may outlive the TxGraph they were
67 : : * created for. */
68 : : [[nodiscard]] virtual Ref AddTransaction(const FeePerWeight& feerate) noexcept = 0;
69 : : /** Remove the specified transaction. If a staging graph exists, the removal only happens
70 : : * there. This is a no-op if the transaction was already removed.
71 : : *
72 : : * TxGraph may internally reorder transaction removals with dependency additions for
73 : : * performance reasons. If together with any transaction removal all its descendants, or all
74 : : * its ancestors, are removed as well (which is what always happens in realistic scenarios),
75 : : * this reordering will not affect the behavior of TxGraph.
76 : : *
77 : : * As an example, imagine 3 transactions A,B,C where B depends on A. If a dependency of C on B
78 : : * is added, and then B is deleted, C will still depend on A. If the deletion of B is reordered
79 : : * before the C->B dependency is added, the dependency adding has no effect. If, together with
80 : : * the deletion of B also either A or C is deleted, there is no distinction between the
81 : : * original order case and the reordered case.
82 : : */
83 : : virtual void RemoveTransaction(const Ref& arg) noexcept = 0;
84 : : /** Add a dependency between two specified transactions. If a staging graph exists, the
85 : : * dependency is only added there. Parent may not be a descendant of child already (but may
86 : : * be an ancestor of it already, in which case this is a no-op). If either transaction is
87 : : * already removed, this is a no-op. */
88 : : virtual void AddDependency(const Ref& parent, const Ref& child) noexcept = 0;
89 : : /** Modify the fee of the specified transaction, in both the main graph and the staging
90 : : * graph if it exists. Wherever the transaction does not exist (or was removed), this has no
91 : : * effect. */
92 : : virtual void SetTransactionFee(const Ref& arg, int64_t fee) noexcept = 0;
93 : :
94 : : /** TxGraph is internally lazy, and will not compute many things until they are needed.
95 : : * Calling DoWork will compute everything now, so that future operations are fast. This can be
96 : : * invoked while oversized. */
97 : : virtual void DoWork() noexcept = 0;
98 : :
99 : : /** Create a staging graph (which cannot exist already). This acts as if a full copy of
100 : : * the transaction graph is made, upon which further modifications are made. This copy can
101 : : * be inspected, and then either discarded, or the main graph can be replaced by it by
102 : : * committing it. */
103 : : virtual void StartStaging() noexcept = 0;
104 : : /** Discard the existing active staging graph (which must exist). */
105 : : virtual void AbortStaging() noexcept = 0;
106 : : /** Replace the main graph with the staging graph (which must exist). */
107 : : virtual void CommitStaging() noexcept = 0;
108 : : /** Check whether a staging graph exists. */
109 : : virtual bool HaveStaging() const noexcept = 0;
110 : :
111 : : /** Determine whether the graph is oversized (contains a connected component of more than the
112 : : * configured maximum cluster count). If main_only is false and a staging graph exists, it is
113 : : * queried; otherwise the main graph is queried. Some of the functions below are not available
114 : : * for oversized graphs. The mutators above are always available. Removing a transaction by
115 : : * destroying its Ref while staging exists will not clear main's oversizedness until staging
116 : : * is aborted or committed. */
117 : : virtual bool IsOversized(bool main_only = false) noexcept = 0;
118 : : /** Determine whether arg exists in the graph (i.e., was not removed). If main_only is false
119 : : * and a staging graph exists, it is queried; otherwise the main graph is queried. This is
120 : : * available even for oversized graphs. */
121 : : virtual bool Exists(const Ref& arg, bool main_only = false) noexcept = 0;
122 : : /** Get the individual transaction feerate of transaction arg. Returns the empty FeePerWeight
123 : : * if arg does not exist in either main or staging. This is available even for oversized
124 : : * graphs. */
125 : : virtual FeePerWeight GetIndividualFeerate(const Ref& arg) noexcept = 0;
126 : : /** Get the feerate of the chunk which transaction arg is in, in the main graph. Returns the
127 : : * empty FeePerWeight if arg does not exist in the main graph. The main graph must not be
128 : : * oversized. */
129 : : virtual FeePerWeight GetMainChunkFeerate(const Ref& arg) noexcept = 0;
130 : : /** Get pointers to all transactions in the cluster which arg is in. The transactions are
131 : : * returned in graph order. If main_only is false and a staging graph exists, it is queried;
132 : : * otherwise the main graph is queried. The queried graph must not be oversized. Returns {} if
133 : : * arg does not exist in the queried graph. */
134 : : virtual std::vector<Ref*> GetCluster(const Ref& arg, bool main_only = false) noexcept = 0;
135 : : /** Get pointers to all ancestors of the specified transaction (including the transaction
136 : : * itself), in unspecified order. If main_only is false and a staging graph exists, it is
137 : : * queried; otherwise the main graph is queried. The queried graph must not be oversized.
138 : : * Returns {} if arg does not exist in the graph. */
139 : : virtual std::vector<Ref*> GetAncestors(const Ref& arg, bool main_only = false) noexcept = 0;
140 : : /** Get pointers to all descendants of the specified transaction (including the transaction
141 : : * itself), in unspecified order. If main_only is false and a staging graph exists, it is
142 : : * queried; otherwise the main graph is queried. The queried graph must not be oversized.
143 : : * Returns {} if arg does not exist in the graph. */
144 : : virtual std::vector<Ref*> GetDescendants(const Ref& arg, bool main_only = false) noexcept = 0;
145 : : /** Like GetAncestors, but return the Refs for all transactions in the union of the provided
146 : : * arguments' ancestors (each transaction is only reported once). Refs that do not exist in
147 : : * the queried graph are ignored. */
148 : : virtual std::vector<Ref*> GetAncestorsUnion(std::span<const Ref* const> args, bool main_only = false) noexcept = 0;
149 : : /** Like GetDescendants, but return the Refs for all transactions in the union of the provided
150 : : * arguments' descendants (each transaction is only reported once). Refs that do not exist in
151 : : * the queried graph are ignored. */
152 : : virtual std::vector<Ref*> GetDescendantsUnion(std::span<const Ref* const> args, bool main_only = false) noexcept = 0;
153 : : /** Get the total number of transactions in the graph. If main_only is false and a staging
154 : : * graph exists, it is queried; otherwise the main graph is queried. This is available even
155 : : * for oversized graphs. */
156 : : virtual GraphIndex GetTransactionCount(bool main_only = false) noexcept = 0;
157 : : /** Compare two transactions according to their order in the main graph. Both transactions must
158 : : * be in the main graph. The main graph must not be oversized. */
159 : : virtual std::strong_ordering CompareMainOrder(const Ref& a, const Ref& b) noexcept = 0;
160 : : /** Count the number of distinct clusters that the specified transactions belong to. If
161 : : * main_only is false and a staging graph exists, staging clusters are counted. Otherwise,
162 : : * main clusters are counted. Refs that do not exist in the queried graph are ignored. The
163 : : * queried graph must not be oversized. */
164 : : virtual GraphIndex CountDistinctClusters(std::span<const Ref* const>, bool main_only = false) noexcept = 0;
165 : :
166 : : /** Perform an internal consistency check on this object. */
167 : : virtual void SanityCheck() const = 0;
168 : :
169 : : protected:
170 : : // Allow TxGraph::Ref to call UpdateRef and UnlinkRef.
171 : : friend class TxGraph::Ref;
172 : : /** Inform the TxGraph implementation that a TxGraph::Ref has moved. */
173 : : virtual void UpdateRef(GraphIndex index, Ref& new_location) noexcept = 0;
174 : : /** Inform the TxGraph implementation that a TxGraph::Ref was destroyed. */
175 : : virtual void UnlinkRef(GraphIndex index) noexcept = 0;
176 : : // Allow TxGraph implementations (inheriting from it) to access Ref internals.
177 : 0 : static TxGraph*& GetRefGraph(Ref& arg) noexcept { return arg.m_graph; }
178 [ # # # # : 0 : static TxGraph* GetRefGraph(const Ref& arg) noexcept { return arg.m_graph; }
# # # # #
# # # # #
# # # # #
# # # # #
# # ]
179 : : static GraphIndex& GetRefIndex(Ref& arg) noexcept { return arg.m_index; }
180 [ # # # # : 0 : static GraphIndex GetRefIndex(const Ref& arg) noexcept { return arg.m_index; }
# # # # #
# # # # #
# # # # #
# ]
181 : :
182 : : public:
183 : : class Ref
184 : : {
185 : : // Allow TxGraph's GetRefGraph and GetRefIndex to access internals.
186 : : friend class TxGraph;
187 : : /** Which Graph the Entry lives in. nullptr if this Ref is empty. */
188 : : TxGraph* m_graph = nullptr;
189 : : /** Index into the Graph's m_entries. Only used if m_graph != nullptr. */
190 : : GraphIndex m_index = GraphIndex(-1);
191 : : public:
192 : : /** Construct an empty Ref. Non-empty Refs can only be created using
193 : : * TxGraph::AddTransaction. */
194 : : Ref() noexcept = default;
195 : : /** Destroy this Ref. If it is not empty, the corresponding transaction is removed (in both
196 : : * main and staging, if it exists). */
197 : : virtual ~Ref();
198 : : // Support moving a Ref.
199 : : Ref& operator=(Ref&& other) noexcept;
200 : : Ref(Ref&& other) noexcept;
201 : : // Do not permit copy constructing or copy assignment. A TxGraph entry can have at most one
202 : : // Ref pointing to it.
203 : : Ref& operator=(const Ref&) = delete;
204 : : Ref(const Ref&) = delete;
205 : : };
206 : : };
207 : :
208 : : /** Construct a new TxGraph with the specified limit on transactions within a cluster. That
209 : : * number cannot exceed MAX_CLUSTER_COUNT_LIMIT. */
210 : : std::unique_ptr<TxGraph> MakeTxGraph(unsigned max_cluster_count) noexcept;
211 : :
212 : : #endif // BITCOIN_TXGRAPH_H
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