add read only option for mdbx

Author: josibake

src/dbwrapper.cpp

@@ -420,14 +420,14 @@ MDBXWrapper::MDBXWrapper(const DBParams& params)
     : CDBWrapperBase(params),
     m_db_context{std::make_unique<MDBXContext>()}
 {
-    if (params.wipe_data) {
+    if (params.wipe_data && !params.read_only) {
         LogInfo("Wiping MDBX in %s\n", fs::PathToString(params.path));
         DestroyDB(fs::PathToString(params.path));
     }
 
     TryCreateDirectories(params.path);
 
-    LogPrintf("Opening MDBX in %s\n", fs::PathToString(params.path));
+    LogPrintf("Opening MDBX in %s (read-only: %s)\n", fs::PathToString(params.path), params.read_only ? "yes" : "no");
 
     DBContext().create_params.geometry.pagesize = 16384;
 
@@ -436,17 +436,24 @@ MDBXWrapper::MDBXWrapper(const DBParams& params)
     DBContext().operate_params.options.no_sticky_threads = true;
     DBContext().operate_params.durability = mdbx::env::whole_fragile;
 
+    // Set read-only mode if specified
+    if (params.read_only) {
+        DBContext().operate_params.mode = mdbx::env::mode::readonly;
+    }
+
     // initialize the mdbx environment.
     DBContext().env = mdbx::env_managed(params.path, DBContext().create_params, DBContext().operate_params);
 
     auto txn = DBContext().env.start_read();
     DBContext().map = txn.open_map(nullptr, mdbx::key_mode::usual, mdbx::value_mode::single);
     txn.commit();
 
-    if (params.obfuscate && WriteObfuscateKeyIfNotExists()){
-        LogInfo("Wrote new obfuscate key for %s: %s\n", fs::PathToString(params.path), HexStr(obfuscate_key));
+    if (!params.read_only) {
+        if (params.obfuscate && WriteObfuscateKeyIfNotExists()){
+            LogInfo("Wrote new obfuscate key for %s: %s\n", fs::PathToString(params.path), HexStr(obfuscate_key));
+        }
+        LogInfo("Using obfuscation key for %s: %s\n", fs::PathToString(params.path), HexStr(GetObfuscateKey()));
     }
-    LogInfo("Using obfuscation key for %s: %s\n", fs::PathToString(params.path), HexStr(GetObfuscateKey()));
 }
 
 MDBXWrapper::~MDBXWrapper() = default;

src/dbwrapper.h

@@ -42,6 +42,11 @@ struct DBParams {
     //! If true, store data obfuscated via simple XOR. If false, XOR with a
     //! zero'd byte array.
     bool obfuscate = false;
+    //! Open the database in read-only mode, e.g., from a process outside bitcoind
+    //! Note: leveldb does not support multi-process readers, so it might make
+    //! more sense to have this be a DBOptions flag, since it is implementation
+    //! specific?
+    bool read_only = false;
     //! Passed-through options.
     DBOptions options{};
 };

src/kernel/bitcoinkernel.cpp

@@ -1019,6 +1019,10 @@ void kernel_chainstate_load_options_set(
         chainstate_load_opts->coins_db_in_memory = value;
         return;
     }
+    case kernel_ChainstateLoadOptionType::kernel_READONLY: {
+        chainstate_load_opts->read_only = value;
+        return;
+    }
     } // no default case, so the compiler can warn about missing cases
     assert(false);
 }
@@ -1384,7 +1388,7 @@ bool kernel_chainstate_manager_process_transaction(
 bool kernel_chainstate_manager_process_block(
     const kernel_Context* context_,
     kernel_ChainstateManager* chainman_,
-    kernel_Block* block_, 
+    kernel_Block* block_,
     kernel_ProcessBlockStatus* status)
 {
     auto& chainman{*cast_chainstate_manager(chainman_)};
@@ -1565,7 +1569,7 @@ kernel_BlockHeader* kernel_get_block_header(kernel_Block* block_)
 {
     auto block{cast_cblocksharedpointer(block_)};
     return reinterpret_cast<kernel_BlockHeader*>(new CBlockHeader{(*block)->GetBlockHeader()});
-} 
+}
 
 kernel_BlockHeader* kernel_block_header_create(const unsigned char* raw_block_header, size_t raw_block_header_len)
 {

src/kernel/bitcoinkernel.h

@@ -340,6 +340,7 @@ typedef enum {
     kernel_WIPE_CHAINSTATE_DB_CHAINSTATE_LOAD_OPTION,      //! Set the wipe chainstate option, default is false.
     kernel_BLOCK_TREE_DB_IN_MEMORY_CHAINSTATE_LOAD_OPTION, //! Set the block tree db in memory option, default is false.
     kernel_CHAINSTATE_DB_IN_MEMORY_CHAINSTATE_LOAD_OPTION, //! Set the coins db in memory option, default is false.
+    kernel_READONLY,                                       //! Open the block tree db and coins db in read-only mode, e.g., from a process outside bitcoind
 } kernel_ChainstateLoadOptionType;
 
 /**
@@ -1129,7 +1130,7 @@ kernel_BlockUndo* BITCOINKERNEL_WARN_UNUSED_RESULT kernel_read_block_undo_from_d
 
 /**
  * @brief Validates a passed in block header and on success adds it to the header chain.
- * 
+ *
  * @param[in] chainman Non-null.
  * @param[in] header   Non-null, the header to be validated.
  * @return             True if the header was successfully validated.

src/node/chainstate.cpp

@@ -46,6 +46,7 @@ static ChainstateLoadResult CompleteChainstateInitialization(
         .cache_bytes = static_cast<size_t>(cache_sizes.block_tree_db),
         .memory_only = options.block_tree_db_in_memory,
         .wipe_data = options.wipe_block_tree_db,
+        .read_only = options.read_only,
         .options = chainman.m_options.block_tree_db});
 
     if (options.wipe_block_tree_db) {
@@ -110,7 +111,8 @@ static ChainstateLoadResult CompleteChainstateInitialization(
         chainstate->InitCoinsDB(
             /*cache_size_bytes=*/chainman.m_total_coinsdb_cache * init_cache_fraction,
             /*in_memory=*/options.coins_db_in_memory,
-            /*should_wipe=*/options.wipe_chainstate_db);
+            /*should_wipe=*/options.wipe_chainstate_db,
+            /*read_only=*/options.read_only);
 
         if (options.coins_error_cb) {
             chainstate->CoinsErrorCatcher().AddReadErrCallback(options.coins_error_cb);

src/node/chainstate.h

@@ -30,6 +30,9 @@ struct ChainstateLoadOptions {
     // will cause the chainstate database to be rebuilt starting from genesis.
     bool wipe_chainstate_db{false};
     bool prune{false};
+    // Open the block_tree and coins_db databases in read only mode, e.g., from a
+    // process other than bitcoind
+    bool read_only{false};
     //! Setting require_full_verification to true will require all checks at
     //! check_level (below) to succeed for loading to succeed. Setting it to
     //! false will skip checks if cache is not big enough to run them, so may be

src/test/validation_chainstate_tests.cpp

@@ -29,7 +29,7 @@ BOOST_AUTO_TEST_CASE(validation_chainstate_resize_caches)
     CTxMemPool& mempool = *Assert(m_node.mempool);
     Chainstate& c1 = WITH_LOCK(cs_main, return manager.InitializeChainstate(&mempool));
     c1.InitCoinsDB(
-        /*cache_size_bytes=*/1 << 23, /*in_memory=*/true, /*should_wipe=*/false);
+        /*cache_size_bytes=*/1 << 23, /*in_memory=*/true, /*should_wipe=*/false, /*read_only=*/false);
     WITH_LOCK(::cs_main, c1.InitCoinsCache(1 << 23));
     BOOST_REQUIRE(c1.LoadGenesisBlock()); // Need at least one block loaded to be able to flush caches
 

src/test/validation_chainstatemanager_tests.cpp

@@ -72,7 +72,7 @@ BOOST_FIXTURE_TEST_CASE(chainstatemanager, TestChain100Setup)
     Chainstate& c2 = WITH_LOCK(::cs_main, return manager.ActivateExistingSnapshot(snapshot_blockhash));
     chainstates.push_back(&c2);
     c2.InitCoinsDB(
-        /*cache_size_bytes=*/1 << 23, /*in_memory=*/true, /*should_wipe=*/false);
+        /*cache_size_bytes=*/1 << 23, /*in_memory=*/true, /*should_wipe=*/false, /*read_only=*/false);
     {
         LOCK(::cs_main);
         c2.InitCoinsCache(1 << 23);
@@ -138,7 +138,7 @@ BOOST_FIXTURE_TEST_CASE(chainstatemanager_rebalance_caches, TestChain100Setup)
     Chainstate& c2 = WITH_LOCK(cs_main, return manager.ActivateExistingSnapshot(*snapshot_base->phashBlock));
     chainstates.push_back(&c2);
     c2.InitCoinsDB(
-        /*cache_size_bytes=*/1 << 23, /*in_memory=*/true, /*should_wipe=*/false);
+        /*cache_size_bytes=*/1 << 23, /*in_memory=*/true, /*should_wipe=*/false, /*read_only=*/false);
 
     // Reset IBD state so IsInitialBlockDownload() returns true and causes
     // MaybeRebalancesCaches() to prioritize the snapshot chainstate, giving it

src/validation.cpp

@@ -1961,6 +1961,7 @@ void Chainstate::InitCoinsDB(
     size_t cache_size_bytes,
     bool in_memory,
     bool should_wipe,
+    bool read_only,
     fs::path leveldb_name)
 {
     if (m_from_snapshot_blockhash) {
@@ -1974,6 +1975,7 @@ void Chainstate::InitCoinsDB(
             .memory_only = in_memory,
             .wipe_data = should_wipe,
             .obfuscate = true,
+            .read_only = read_only,
             .options = m_chainman.m_options.coins_db},
         m_chainman.m_options.coins_view);
 }

src/validation.h

@@ -574,6 +574,7 @@ class Chainstate
         size_t cache_size_bytes,
         bool in_memory,
         bool should_wipe,
+        bool read_only,
         fs::path leveldb_name = "chainstate");
 
     //! Initialize the in-memory coins cache (to be done after the health of the on-disk database