feat: assumeutxo: enable loading snapshot in memory

Author: kevkevinpal

src/rpc/blockchain.cpp

@@ -2746,10 +2746,8 @@ static RPCHelpMan loadtxoutset()
         "You can find more information on this process in the `assumeutxo` design "
         "document (<https://github.com/bitcoin/bitcoin/blob/master/doc/design/assumeutxo.md>).",
         {
-            {"path",
-                RPCArg::Type::STR,
-                RPCArg::Optional::NO,
-                "path to the snapshot file. If relative, will be prefixed by datadir."},
+            {"path", RPCArg::Type::STR, RPCArg::Optional::NO, "path to the snapshot file. If relative, will be prefixed by datadir."},
+            {"in_memory", RPCArg::Type::BOOL, RPCArg::Default{false}, "should we load snapshot in memory."},
         },
         RPCResult{
             RPCResult::Type::OBJ, "", "",
@@ -2768,6 +2766,10 @@ static RPCHelpMan loadtxoutset()
     NodeContext& node = EnsureAnyNodeContext(request.context);
     ChainstateManager& chainman = EnsureChainman(node);
     fs::path path{AbsPathForConfigVal(EnsureArgsman(node), fs::u8path(request.params[0].get_str()))};
+    bool in_memory = true;
+    if (!request.params[1].isNull()) {
+        in_memory = request.params[1].get_bool();
+    }
 
     FILE* file{fsbridge::fopen(path, "rb")};
     AutoFile afile{file};
@@ -2794,7 +2796,7 @@ static RPCHelpMan loadtxoutset()
             strprintf("The base block header (%s) must appear in the headers chain. Make sure all headers are syncing, and call this RPC again.",
                       base_blockhash.ToString()));
     }
-    if (!chainman.ActivateSnapshot(afile, metadata, false)) {
+    if (!chainman.ActivateSnapshot(afile, metadata, in_memory)) {
         throw JSONRPCError(RPC_INTERNAL_ERROR, "Unable to load UTXO snapshot " + fs::PathToString(path));
     }
 

test/functional/feature_assumeutxo.py

@@ -397,6 +397,26 @@ def check_tx_counts(final: bool) -> None:
             assert_equal(loaded['coins_loaded'], SNAPSHOT_BASE_HEIGHT)
             assert_equal(loaded['base_height'], SNAPSHOT_BASE_HEIGHT)
 
+
+        normal, snapshot = n2.getchainstates()['chainstates']
+        assert_equal(normal['blocks'], START_HEIGHT)
+        assert_equal(normal.get('snapshot_blockhash'), None)
+        assert_equal(normal['validated'], True)
+        assert_equal(snapshot['blocks'], SNAPSHOT_BASE_HEIGHT)
+        assert_equal(snapshot['snapshot_blockhash'], dump_output['base_hash'])
+        assert_equal(snapshot['validated'], False)
+
+        for reindex_arg in ['-reindex=1', '-reindex-chainstate=1']:
+            self.log.info(f"Check that restarting with {reindex_arg} will delete the snapshot chainstate and load in_memory=true works")
+            self.restart_node(2, extra_args=[reindex_arg, *self.extra_args[2]])
+            assert_equal(1, len(n2.getchainstates()["chainstates"]))
+            for i in range(1, 300):
+                block = n0.getblock(n0.getblockhash(i), 0)
+                n2.submitheader(block)
+            loaded = n2.loadtxoutset(dump_output['path'], True)
+            assert_equal(loaded['coins_loaded'], SNAPSHOT_BASE_HEIGHT)
+            assert_equal(loaded['base_height'], SNAPSHOT_BASE_HEIGHT)
+
         normal, snapshot = n2.getchainstates()['chainstates']
         assert_equal(normal['blocks'], START_HEIGHT)
         assert_equal(normal.get('snapshot_blockhash'), None)