rpc: add getchainstates

Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

doc/release-notes-27596.md

@@ -24,3 +24,5 @@ are always checked by hash.
 
 You can find more information on this process in the `assumeutxo` design
 document (<https://github.com/bitcoin/bitcoin/blob/master/doc/design/assumeutxo.md>).
+
+`getchainstates` has been added to aid in monitoring the assumeutxo sync process.

src/rpc/blockchain.cpp

@@ -2799,6 +2799,79 @@ static RPCHelpMan loadtxoutset()
     };
 }
 
+const std::vector<RPCResult> RPCHelpForChainstate{
+    {RPCResult::Type::NUM, "blocks", "number of blocks in this chainstate"},
+    {RPCResult::Type::STR_HEX, "bestblockhash", "blockhash of the tip"},
+    {RPCResult::Type::NUM, "difficulty", "difficulty of the tip"},
+    {RPCResult::Type::NUM, "verificationprogress", "progress towards the network tip"},
+    {RPCResult::Type::STR_HEX, "snapshot_blockhash", /*optional=*/true, "the base block of the snapshot this chainstate is based on, if any"},
+    {RPCResult::Type::NUM, "coins_db_cache_bytes", "size of the coinsdb cache"},
+    {RPCResult::Type::NUM, "coins_tip_cache_bytes", "size of the coinstip cache"},
+};
+
+static RPCHelpMan getchainstates()
+{
+return RPCHelpMan{
+        "getchainstates",
+        "\nReturn information about chainstates.\n",
+        {},
+        RPCResult{
+            RPCResult::Type::OBJ, "", "", {
+                {RPCResult::Type::NUM, "headers", "the number of headers seen so far"},
+                {RPCResult::Type::OBJ, "normal", /*optional=*/true, "fully validated chainstate containing blocks this node has validated starting from the genesis block", RPCHelpForChainstate},
+                {RPCResult::Type::OBJ, "snapshot", /*optional=*/true, "only present if an assumeutxo snapshot is loaded. Partially validated chainstate containing blocks this node has validated starting from the snapshot. After the snapshot is validated (when the 'normal' chainstate advances far enough to validate it), this chainstate will replace and become the 'normal' chainstate.", RPCHelpForChainstate},
+            }
+        },
+        RPCExamples{
+            HelpExampleCli("getchainstates", "")
+    + HelpExampleRpc("getchainstates", "")
+        },
+        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
+{
+    LOCK(cs_main);
+    UniValue obj(UniValue::VOBJ);
+
+    NodeContext& node = EnsureAnyNodeContext(request.context);
+    ChainstateManager& chainman = *node.chainman;
+
+    auto make_chain_data = [&](const Chainstate& cs) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
+        AssertLockHeld(::cs_main);
+        UniValue data(UniValue::VOBJ);
+        if (!cs.m_chain.Tip()) {
+            return data;
+        }
+        const CChain& chain = cs.m_chain;
+        const CBlockIndex* tip = chain.Tip();
+
+        data.pushKV("blocks",                (int)chain.Height());
+        data.pushKV("bestblockhash",         tip->GetBlockHash().GetHex());
+        data.pushKV("difficulty",            (double)GetDifficulty(tip));
+        data.pushKV("verificationprogress",  GuessVerificationProgress(Params().TxData(), tip));
+        data.pushKV("coins_db_cache_bytes",  cs.m_coinsdb_cache_size_bytes);
+        data.pushKV("coins_tip_cache_bytes", cs.m_coinstip_cache_size_bytes);
+        if (cs.m_from_snapshot_blockhash) {
+            data.pushKV("snapshot_blockhash", cs.m_from_snapshot_blockhash->ToString());
+        }
+        return data;
+    };
+
+    if (chainman.GetAll().size() > 1) {
+        for (Chainstate* chainstate : chainman.GetAll()) {
+            obj.pushKV(
+                chainstate->m_from_snapshot_blockhash ? "snapshot" : "normal",
+                make_chain_data(*chainstate));
+        }
+    } else {
+        obj.pushKV("normal", make_chain_data(chainman.ActiveChainstate()));
+    }
+    obj.pushKV("headers", chainman.m_best_header ? chainman.m_best_header->nHeight : -1);
+
+    return obj;
+}
+    };
+}
+
+
 void RegisterBlockchainRPCCommands(CRPCTable& t)
 {
     static const CRPCCommand commands[]{
@@ -2824,6 +2897,7 @@ void RegisterBlockchainRPCCommands(CRPCTable& t)
         {"blockchain", &getblockfilter},
         {"blockchain", &dumptxoutset},
         {"blockchain", &loadtxoutset},
+        {"blockchain", &getchainstates},
         {"hidden", &invalidateblock},
         {"hidden", &reconsiderblock},
         {"hidden", &waitfornewblock},

src/test/fuzz/rpc.cpp

@@ -123,6 +123,7 @@ const std::vector<std::string> RPC_COMMANDS_SAFE_FOR_FUZZING{
     "getblockstats",
     "getblocktemplate",
     "getchaintips",
+    "getchainstates",
     "getchaintxstats",
     "getconnectioncount",
     "getdeploymentinfo",