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1 : : // Copyright (c) 2017-2022 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 <util/threadinterrupt.h>
11 : : #include <validationinterface.h>
12 : :
13 : : #include <string>
14 : :
15 : : class CBlock;
16 : : class CBlockIndex;
17 : : class Chainstate;
18 : : class ChainstateManager;
19 : : namespace interfaces {
20 : : class Chain;
21 : : } // namespace interfaces
22 : :
23 : 4 : struct IndexSummary {
24 : : std::string name;
25 : : bool synced{false};
26 : : int best_block_height{0};
27 : : uint256 best_block_hash;
28 : : };
29 : :
30 : : /**
31 : : * Base class for indices of blockchain data. This implements
32 : : * CValidationInterface and ensures blocks are indexed sequentially according
33 : : * to their position in the active chain.
34 : : *
35 : : * In the presence of multiple chainstates (i.e. if a UTXO snapshot is loaded),
36 : : * only the background "IBD" chainstate will be indexed to avoid building the
37 : : * index out of order. When the background chainstate completes validation, the
38 : : * index will be reinitialized and indexing will continue.
39 : : */
40 : : class BaseIndex : public CValidationInterface
41 : : {
42 : : protected:
43 : : /**
44 : : * The database stores a block locator of the chain the database is synced to
45 : : * so that the index can efficiently determine the point it last stopped at.
46 : : * A locator is used instead of a simple hash of the chain tip because blocks
47 : : * and block index entries may not be flushed to disk until after this database
48 : : * is updated.
49 : : */
50 : 8 : class DB : public CDBWrapper
51 : : {
52 : : public:
53 : : DB(const fs::path& path, size_t n_cache_size,
54 : : bool f_memory = false, bool f_wipe = false, bool f_obfuscate = false);
55 : :
56 : : /// Read block locator of the chain that the index is in sync with.
57 : : bool ReadBestBlock(CBlockLocator& locator) const;
58 : :
59 : : /// Write block locator of the chain that the index is in sync with.
60 : : void WriteBestBlock(CDBBatch& batch, const CBlockLocator& locator);
61 : : };
62 : :
63 : : private:
64 : : /// Whether the index has been initialized or not.
65 : : std::atomic<bool> m_init{false};
66 : : /// Whether the index is in sync with the main chain. The flag is flipped
67 : : /// from false to true once, after which point this starts processing
68 : : /// ValidationInterface notifications to stay in sync.
69 : : ///
70 : : /// Note that this will latch to true *immediately* upon startup if
71 : : /// `m_chainstate->m_chain` is empty, which will be the case upon startup
72 : : /// with an empty datadir if, e.g., `-txindex=1` is specified.
73 : : std::atomic<bool> m_synced{false};
74 : :
75 : : /// The last block in the chain that the index is in sync with.
76 : : std::atomic<const CBlockIndex*> m_best_block_index{nullptr};
77 : :
78 : : std::thread m_thread_sync;
79 : : CThreadInterrupt m_interrupt;
80 : :
81 : : /// Write the current index state (eg. chain block locator and subclass-specific items) to disk.
82 : : ///
83 : : /// Recommendations for error handling:
84 : : /// If called on a successor of the previous committed best block in the index, the index can
85 : : /// continue processing without risk of corruption, though the index state will need to catch up
86 : : /// from further behind on reboot. If the new state is not a successor of the previous state (due
87 : : /// to a chain reorganization), the index must halt until Commit succeeds or else it could end up
88 : : /// getting corrupted.
89 : : bool Commit();
90 : :
91 : : /// Loop over disconnected blocks and call CustomRewind.
92 : : bool Rewind(const CBlockIndex* current_tip, const CBlockIndex* new_tip);
93 : :
94 : : virtual bool AllowPrune() const = 0;
95 : :
96 : : template <typename... Args>
97 : : void FatalErrorf(const char* fmt, const Args&... args);
98 : :
99 : : protected:
100 : : std::unique_ptr<interfaces::Chain> m_chain;
101 : : Chainstate* m_chainstate{nullptr};
102 : : const std::string m_name;
103 : :
104 : : void BlockConnected(ChainstateRole role, const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex) override;
105 : :
106 : : void ChainStateFlushed(ChainstateRole role, const CBlockLocator& locator) override;
107 : :
108 : : /// Initialize internal state from the database and block index.
109 : 1 : [[nodiscard]] virtual bool CustomInit(const std::optional<interfaces::BlockKey>& block) { return true; }
110 : :
111 : : /// Write update index entries for a newly connected block.
112 : 0 : [[nodiscard]] virtual bool CustomAppend(const interfaces::BlockInfo& block) { return true; }
113 : :
114 : : /// Virtual method called internally by Commit that can be overridden to atomically
115 : : /// commit more index state.
116 : 2 : virtual bool CustomCommit(CDBBatch& batch) { return true; }
117 : :
118 : : /// Rewind index to an earlier chain tip during a chain reorg. The tip must
119 : : /// be an ancestor of the current best block.
120 : 0 : [[nodiscard]] virtual bool CustomRewind(const interfaces::BlockKey& current_tip, const interfaces::BlockKey& new_tip) { return true; }
121 : :
122 : : virtual DB& GetDB() const = 0;
123 : :
124 : : /// Update the internal best block index as well as the prune lock.
125 : : void SetBestBlockIndex(const CBlockIndex* block);
126 : :
127 : : public:
128 : : BaseIndex(std::unique_ptr<interfaces::Chain> chain, std::string name);
129 : : /// Destructor interrupts sync thread if running and blocks until it exits.
130 : : virtual ~BaseIndex();
131 : :
132 : : /// Get the name of the index for display in logs.
133 [ + - + - : 52 : const std::string& GetName() const LIFETIMEBOUND { return m_name; }
+ - - - ]
134 : :
135 : : /// Blocks the current thread until the index is caught up to the current
136 : : /// state of the block chain. This only blocks if the index has gotten in
137 : : /// sync once and only needs to process blocks in the ValidationInterface
138 : : /// queue. If the index is catching up from far behind, this method does
139 : : /// not block and immediately returns false.
140 : : bool BlockUntilSyncedToCurrentChain() const LOCKS_EXCLUDED(::cs_main);
141 : :
142 : : void Interrupt();
143 : :
144 : : /// Initializes the sync state and registers the instance to the
145 : : /// validation interface so that it stays in sync with blockchain updates.
146 : : [[nodiscard]] bool Init();
147 : :
148 : : /// Starts the initial sync process on a background thread.
149 : : [[nodiscard]] bool StartBackgroundSync();
150 : :
151 : : /// Sync the index with the block index starting from the current best block.
152 : : /// Intended to be run in its own thread, m_thread_sync, and can be
153 : : /// interrupted with m_interrupt. Once the index gets in sync, the m_synced
154 : : /// flag is set and the BlockConnected ValidationInterface callback takes
155 : : /// over and the sync thread exits.
156 : : void Sync();
157 : :
158 : : /// Stops the instance from staying in sync with blockchain updates.
159 : : void Stop();
160 : :
161 : : /// Get a summary of the index and its state.
162 : : IndexSummary GetSummary() const;
163 : : };
164 : :
165 : : #endif // BITCOIN_INDEX_BASE_H
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