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1 : : // Copyright (c) 2017-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_INDEX_BASE_H
6 : : #define BITCOIN_INDEX_BASE_H
7 : :
8 : : #include <dbwrapper.h>
9 : : #include <interfaces/chain.h>
10 : : #include <interfaces/types.h>
11 : : #include <util/string.h>
12 : : #include <util/threadinterrupt.h>
13 : : #include <validationinterface.h>
14 : :
15 : : #include <string>
16 : :
17 : : class CBlock;
18 : : class CBlockIndex;
19 : : class Chainstate;
20 : : class ChainstateManager;
21 : : namespace interfaces {
22 : : class Chain;
23 : : } // namespace interfaces
24 : :
25 : 4 : struct IndexSummary {
26 : : std::string name;
27 : : bool synced{false};
28 : : int best_block_height{0};
29 : : uint256 best_block_hash;
30 : : };
31 : :
32 : : /**
33 : : * Base class for indices of blockchain data. This implements
34 : : * CValidationInterface and ensures blocks are indexed sequentially according
35 : : * to their position in the active chain.
36 : : *
37 : : * In the presence of multiple chainstates (i.e. if a UTXO snapshot is loaded),
38 : : * only the background "IBD" chainstate will be indexed to avoid building the
39 : : * index out of order. When the background chainstate completes validation, the
40 : : * index will be reinitialized and indexing will continue.
41 : : */
42 : : class BaseIndex : public CValidationInterface
43 : : {
44 : : protected:
45 : : /**
46 : : * The database stores a block locator of the chain the database is synced to
47 : : * so that the index can efficiently determine the point it last stopped at.
48 : : * A locator is used instead of a simple hash of the chain tip because blocks
49 : : * and block index entries may not be flushed to disk until after this database
50 : : * is updated.
51 : : */
52 : 8 : class DB : public CDBWrapper
53 : : {
54 : : public:
55 : : DB(const fs::path& path, size_t n_cache_size,
56 : : bool f_memory = false, bool f_wipe = false, bool f_obfuscate = false);
57 : :
58 : : /// Read block locator of the chain that the index is in sync with.
59 : : bool ReadBestBlock(CBlockLocator& locator) const;
60 : :
61 : : /// Write block locator of the chain that the index is in sync with.
62 : : void WriteBestBlock(CDBBatch& batch, const CBlockLocator& locator);
63 : : };
64 : :
65 : : private:
66 : : /// Whether the index has been initialized or not.
67 : : std::atomic<bool> m_init{false};
68 : : /// Whether the index is in sync with the main chain. The flag is flipped
69 : : /// from false to true once, after which point this starts processing
70 : : /// ValidationInterface notifications to stay in sync.
71 : : ///
72 : : /// Note that this will latch to true *immediately* upon startup if
73 : : /// `m_chainstate->m_chain` is empty, which will be the case upon startup
74 : : /// with an empty datadir if, e.g., `-txindex=1` is specified.
75 : : std::atomic<bool> m_synced{false};
76 : :
77 : : /// The last block in the chain that the index is in sync with.
78 : : std::atomic<const CBlockIndex*> m_best_block_index{nullptr};
79 : :
80 : : std::thread m_thread_sync;
81 : : CThreadInterrupt m_interrupt;
82 : :
83 : : /// Write the current index state (eg. chain block locator and subclass-specific items) to disk.
84 : : ///
85 : : /// Recommendations for error handling:
86 : : /// If called on a successor of the previous committed best block in the index, the index can
87 : : /// continue processing without risk of corruption, though the index state will need to catch up
88 : : /// from further behind on reboot. If the new state is not a successor of the previous state (due
89 : : /// to a chain reorganization), the index must halt until Commit succeeds or else it could end up
90 : : /// getting corrupted.
91 : : bool Commit();
92 : :
93 : : /// Loop over disconnected blocks and call CustomRewind.
94 : : bool Rewind(const CBlockIndex* current_tip, const CBlockIndex* new_tip);
95 : :
96 : : virtual bool AllowPrune() const = 0;
97 : :
98 : : template <typename... Args>
99 : : void FatalErrorf(util::ConstevalFormatString<sizeof...(Args)> fmt, const Args&... args);
100 : :
101 : : protected:
102 : : std::unique_ptr<interfaces::Chain> m_chain;
103 : : Chainstate* m_chainstate{nullptr};
104 : : const std::string m_name;
105 : :
106 : : void BlockConnected(ChainstateRole role, const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex) override;
107 : :
108 : : void ChainStateFlushed(ChainstateRole role, const CBlockLocator& locator) override;
109 : :
110 : : /// Initialize internal state from the database and block index.
111 : 1 : [[nodiscard]] virtual bool CustomInit(const std::optional<interfaces::BlockRef>& block) { return true; }
112 : :
113 : : /// Write update index entries for a newly connected block.
114 : 0 : [[nodiscard]] virtual bool CustomAppend(const interfaces::BlockInfo& block) { return true; }
115 : :
116 : : /// Virtual method called internally by Commit that can be overridden to atomically
117 : : /// commit more index state.
118 : 2 : virtual bool CustomCommit(CDBBatch& batch) { return true; }
119 : :
120 : : /// Rewind index to an earlier chain tip during a chain reorg. The tip must
121 : : /// be an ancestor of the current best block.
122 : 0 : [[nodiscard]] virtual bool CustomRewind(const interfaces::BlockRef& current_tip, const interfaces::BlockRef& new_tip) { return true; }
123 : :
124 : : virtual DB& GetDB() const = 0;
125 : :
126 : : /// Update the internal best block index as well as the prune lock.
127 : : void SetBestBlockIndex(const CBlockIndex* block);
128 : :
129 : : public:
130 : : BaseIndex(std::unique_ptr<interfaces::Chain> chain, std::string name);
131 : : /// Destructor interrupts sync thread if running and blocks until it exits.
132 : : virtual ~BaseIndex();
133 : :
134 : : /// Get the name of the index for display in logs.
135 [ + - + - : 52 : const std::string& GetName() const LIFETIMEBOUND { return m_name; }
+ - - - ]
136 : :
137 : : /// Blocks the current thread until the index is caught up to the current
138 : : /// state of the block chain. This only blocks if the index has gotten in
139 : : /// sync once and only needs to process blocks in the ValidationInterface
140 : : /// queue. If the index is catching up from far behind, this method does
141 : : /// not block and immediately returns false.
142 : : bool BlockUntilSyncedToCurrentChain() const LOCKS_EXCLUDED(::cs_main);
143 : :
144 : : void Interrupt();
145 : :
146 : : /// Initializes the sync state and registers the instance to the
147 : : /// validation interface so that it stays in sync with blockchain updates.
148 : : [[nodiscard]] bool Init();
149 : :
150 : : /// Starts the initial sync process on a background thread.
151 : : [[nodiscard]] bool StartBackgroundSync();
152 : :
153 : : /// Sync the index with the block index starting from the current best block.
154 : : /// Intended to be run in its own thread, m_thread_sync, and can be
155 : : /// interrupted with m_interrupt. Once the index gets in sync, the m_synced
156 : : /// flag is set and the BlockConnected ValidationInterface callback takes
157 : : /// over and the sync thread exits.
158 : : void Sync();
159 : :
160 : : /// Stops the instance from staying in sync with blockchain updates.
161 : : void Stop();
162 : :
163 : : /// Get a summary of the index and its state.
164 : : IndexSummary GetSummary() const;
165 : : };
166 : :
167 : : #endif // BITCOIN_INDEX_BASE_H
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