Merge #18740: Remove g_rpc_node global

b3f7f375ef refactor: Remove g_rpc_node global (Russell Yanofsky)
ccb5059ee8 scripted-diff: Remove g_rpc_node references (Russell Yanofsky)
6fca33b2ed refactor: Pass NodeContext to RPC and REST methods through util::Ref (Russell Yanofsky)
691c817b34 Add util::Ref class as temporary alternative for c++17 std::any (Russell Yanofsky)

Pull request description:

  This PR removes the `g_rpc_node` global, to get same benefits we see removing other globals and make RPC code more testable, modular, and reusable.

  This uses a hybrid of the approaches suggested in #17548. Instead of using `std::any`, which isn't available in c++11, or `void*`, which isn't type safe, it uses a small new `util::Ref` helper class, which acts like a simplified `std::any` that only holds references, not values.

  Motivation for writing this was to provide an simpler alternative to #18647 by Harris Brakmić (brakmic) which avoids some shortcomings of that PR (https://github.com/bitcoin/bitcoin/pull/18647#issuecomment-617878826)

ACKs for top commit:
  MarcoFalke:
    re-ACK b3f7f375ef, only change is adding back const and more tests 🚾
  ajtowns:
    ACK b3f7f375ef

Tree-SHA512: 56292268a001bdbe34d641db1180c215351503966ff451e55cc96c9137f1d262225d7d7733de9c9da7ce7d7a4b34213a98c2476266b58c89dbbb0f3cb5aa5d70

src/Makefile.am

@@ -227,6 +227,7 @@ BITCOIN_CORE_H = \
   util/message.h \
   util/moneystr.h \
   util/rbf.h \
+  util/ref.h \
   util/settings.h \
   util/string.h \
   util/threadnames.h \

src/Makefile.test.include

@@ -229,6 +229,7 @@ BITCOIN_TESTS =\
   test/prevector_tests.cpp \
   test/raii_event_tests.cpp \
   test/random_tests.cpp \
+  test/ref_tests.cpp \
   test/reverselock_tests.cpp \
   test/rpc_tests.cpp \
   test/sanity_tests.cpp \

src/bitcoind.cpp

@@ -16,6 +16,7 @@
 #include <noui.h>
 #include <shutdown.h>
 #include <ui_interface.h>
+#include <util/ref.h>
 #include <util/strencodings.h>
 #include <util/system.h>
 #include <util/threadnames.h>
@@ -77,6 +78,7 @@ static bool AppInit(int argc, char* argv[])
         return true;
     }
 
+    util::Ref context{node};
     try
     {
         if (!CheckDataDirOption()) {
@@ -145,7 +147,7 @@ static bool AppInit(int argc, char* argv[])
             // If locking the data directory failed, exit immediately
             return false;
         }
-        fRet = AppInitMain(node);
+        fRet = AppInitMain(context, node);
     }
     catch (const std::exception& e) {
         PrintExceptionContinue(&e, "AppInit()");

src/httprpc.cpp

@@ -150,7 +150,7 @@ static bool RPCAuthorized(const std::string& strAuth, std::string& strAuthUserna
     return multiUserAuthorized(strUserPass);
 }
 
-static bool HTTPReq_JSONRPC(HTTPRequest* req, const std::string &)
+static bool HTTPReq_JSONRPC(const util::Ref& context, HTTPRequest* req)
 {
     // JSONRPC handles only POST
     if (req->GetRequestMethod() != HTTPRequest::POST) {
@@ -165,7 +165,7 @@ static bool HTTPReq_JSONRPC(HTTPRequest* req, const std::string &)
         return false;
     }
 
-    JSONRPCRequest jreq;
+    JSONRPCRequest jreq(context);
     jreq.peerAddr = req->GetPeer().ToString();
     if (!RPCAuthorized(authHeader.second, jreq.authUser)) {
         LogPrintf("ThreadRPCServer incorrect password attempt from %s\n", jreq.peerAddr);
@@ -284,15 +284,16 @@ static bool InitRPCAuthentication()
     return true;
 }
 
-bool StartHTTPRPC()
+bool StartHTTPRPC(const util::Ref& context)
 {
     LogPrint(BCLog::RPC, "Starting HTTP RPC server\n");
     if (!InitRPCAuthentication())
         return false;
 
-    RegisterHTTPHandler("/", true, HTTPReq_JSONRPC);
+    auto handle_rpc = [&context](HTTPRequest* req, const std::string&) { return HTTPReq_JSONRPC(context, req); };
+    RegisterHTTPHandler("/", true, handle_rpc);
     if (g_wallet_init_interface.HasWalletSupport()) {
-        RegisterHTTPHandler("/wallet/", false, HTTPReq_JSONRPC);
+        RegisterHTTPHandler("/wallet/", false, handle_rpc);
     }
     struct event_base* eventBase = EventBase();
     assert(eventBase);

src/httprpc.h

@@ -5,11 +5,14 @@
 #ifndef BITCOIN_HTTPRPC_H
 #define BITCOIN_HTTPRPC_H
 
+namespace util {
+class Ref;
+} // namespace util
 
 /** Start HTTP RPC subsystem.
  * Precondition; HTTP and RPC has been started.
  */
-bool StartHTTPRPC();
+bool StartHTTPRPC(const util::Ref& context);
 /** Interrupt HTTP RPC subsystem.
  */
 void InterruptHTTPRPC();
@@ -21,7 +24,7 @@ void StopHTTPRPC();
 /** Start HTTP REST subsystem.
  * Precondition; HTTP and RPC has been started.
  */
-void StartREST();
+void StartREST(const util::Ref& context);
 /** Interrupt RPC REST subsystem.
  */
 void InterruptREST();

src/init.cpp

@@ -784,16 +784,16 @@ static bool InitSanityCheck()
     return true;
 }
 
-static bool AppInitServers()
+static bool AppInitServers(const util::Ref& context)
 {
     RPCServer::OnStarted(&OnRPCStarted);
     RPCServer::OnStopped(&OnRPCStopped);
     if (!InitHTTPServer())
         return false;
     StartRPC();
-    if (!StartHTTPRPC())
+    if (!StartHTTPRPC(context))
         return false;
-    if (gArgs.GetBoolArg("-rest", DEFAULT_REST_ENABLE)) StartREST();
+    if (gArgs.GetBoolArg("-rest", DEFAULT_REST_ENABLE)) StartREST(context);
     StartHTTPServer();
     return true;
 }
@@ -1238,7 +1238,7 @@ bool AppInitLockDataDirectory()
     return true;
 }
 
-bool AppInitMain(NodeContext& node)
+bool AppInitMain(const util::Ref& context, NodeContext& node)
 {
     const CChainParams& chainparams = Params();
     // ********************************************************* Step 4a: application initialization
@@ -1340,7 +1340,6 @@ bool AppInitMain(NodeContext& node)
     for (const auto& client : node.chain_clients) {
         client->registerRpcs();
     }
-    g_rpc_node = &node;
 #if ENABLE_ZMQ
     RegisterZMQRPCCommands(tableRPC);
 #endif
@@ -1353,7 +1352,7 @@ bool AppInitMain(NodeContext& node)
     if (gArgs.GetBoolArg("-server", false))
     {
         uiInterface.InitMessage_connect(SetRPCWarmupStatus);
-        if (!AppInitServers())
+        if (!AppInitServers(context))
             return InitError(_("Unable to start HTTP server. See debug log for details."));
     }
 

src/init.h

@@ -14,6 +14,9 @@ struct NodeContext;
 namespace boost {
 class thread_group;
 } // namespace boost
+namespace util {
+class Ref;
+} // namespace util
 
 /** Interrupt threads */
 void Interrupt(NodeContext& node);
@@ -51,7 +54,7 @@ bool AppInitLockDataDirectory();
  * @note This should only be done after daemonization. Call Shutdown() if this function fails.
  * @pre Parameters should be parsed and config file should be read, AppInitLockDataDirectory should have been called.
  */
-bool AppInitMain(NodeContext& node);
+bool AppInitMain(const util::Ref& context, NodeContext& node);
 
 /**
  * Register all arguments with the ArgsManager

src/interfaces/node.cpp

@@ -27,6 +27,7 @@
 #include <sync.h>
 #include <txmempool.h>
 #include <ui_interface.h>
+#include <util/ref.h>
 #include <util/system.h>
 #include <util/translation.h>
 #include <validation.h>
@@ -80,7 +81,7 @@ public:
     bool appInitMain() override
     {
         m_context.chain = MakeChain(m_context);
-        return AppInitMain(m_context);
+        return AppInitMain(m_context_ref, m_context);
     }
     void appShutdown() override
     {
@@ -225,7 +226,7 @@ public:
     CFeeRate getDustRelayFee() override { return ::dustRelayFee; }
     UniValue executeRpc(const std::string& command, const UniValue& params, const std::string& uri) override
     {
-        JSONRPCRequest req;
+        JSONRPCRequest req(m_context_ref);
         req.params = params;
         req.strMethod = command;
         req.URI = uri;
@@ -323,6 +324,7 @@ public:
     }
     NodeContext* context() override { return &m_context; }
     NodeContext m_context;
+    util::Ref m_context_ref{m_context};
 };
 
 } // namespace

src/rest.cpp

@@ -18,6 +18,7 @@
 #include <sync.h>
 #include <txmempool.h>
 #include <util/check.h>
+#include <util/ref.h>
 #include <util/strencodings.h>
 #include <validation.h>
 #include <version.h>
@@ -75,13 +76,14 @@ static bool RESTERR(HTTPRequest* req, enum HTTPStatusCode status, std::string me
  * @param[in]  req the HTTP request
  * return pointer to the mempool or nullptr if no mempool found
  */
-static CTxMemPool* GetMemPool(HTTPRequest* req)
+static CTxMemPool* GetMemPool(const util::Ref& context, HTTPRequest* req)
 {
-    if (!g_rpc_node || !g_rpc_node->mempool) {
+    NodeContext* node = context.Has<NodeContext>() ? &context.Get<NodeContext>() : nullptr;
+    if (!node || !node->mempool) {
         RESTERR(req, HTTP_NOT_FOUND, "Mempool disabled or instance not found");
         return nullptr;
     }
-    return g_rpc_node->mempool;
+    return node->mempool;
 }
 
 static RetFormat ParseDataFormat(std::string& param, const std::string& strReq)
@@ -129,7 +131,8 @@ static bool CheckWarmup(HTTPRequest* req)
     return true;
 }
 
-static bool rest_headers(HTTPRequest* req,
+static bool rest_headers(const util::Ref& context,
+                         HTTPRequest* req,
                          const std::string& strURIPart)
 {
     if (!CheckWarmup(req))
@@ -270,12 +273,12 @@ static bool rest_block(HTTPRequest* req,
     }
 }
 
-static bool rest_block_extended(HTTPRequest* req, const std::string& strURIPart)
+static bool rest_block_extended(const util::Ref& context, HTTPRequest* req, const std::string& strURIPart)
 {
     return rest_block(req, strURIPart, true);
 }
 
-static bool rest_block_notxdetails(HTTPRequest* req, const std::string& strURIPart)
+static bool rest_block_notxdetails(const util::Ref& context, HTTPRequest* req, const std::string& strURIPart)
 {
     return rest_block(req, strURIPart, false);
 }
@@ -283,7 +286,7 @@ static bool rest_block_notxdetails(HTTPRequest* req, const std::string& strURIPa
 // A bit of a hack - dependency on a function defined in rpc/blockchain.cpp
 UniValue getblockchaininfo(const JSONRPCRequest& request);
 
-static bool rest_chaininfo(HTTPRequest* req, const std::string& strURIPart)
+static bool rest_chaininfo(const util::Ref& context, HTTPRequest* req, const std::string& strURIPart)
 {
     if (!CheckWarmup(req))
         return false;
@@ -292,7 +295,7 @@ static bool rest_chaininfo(HTTPRequest* req, const std::string& strURIPart)
 
     switch (rf) {
     case RetFormat::JSON: {
-        JSONRPCRequest jsonRequest;
+        JSONRPCRequest jsonRequest(context);
         jsonRequest.params = UniValue(UniValue::VARR);
         UniValue chainInfoObject = getblockchaininfo(jsonRequest);
         std::string strJSON = chainInfoObject.write() + "\n";
@@ -306,11 +309,11 @@ static bool rest_chaininfo(HTTPRequest* req, const std::string& strURIPart)
     }
 }
 
-static bool rest_mempool_info(HTTPRequest* req, const std::string& strURIPart)
+static bool rest_mempool_info(const util::Ref& context, HTTPRequest* req, const std::string& strURIPart)
 {
     if (!CheckWarmup(req))
         return false;
-    const CTxMemPool* mempool = GetMemPool(req);
+    const CTxMemPool* mempool = GetMemPool(context, req);
     if (!mempool) return false;
     std::string param;
     const RetFormat rf = ParseDataFormat(param, strURIPart);
@@ -330,10 +333,10 @@ static bool rest_mempool_info(HTTPRequest* req, const std::string& strURIPart)
     }
 }
 
-static bool rest_mempool_contents(HTTPRequest* req, const std::string& strURIPart)
+static bool rest_mempool_contents(const util::Ref& context, HTTPRequest* req, const std::string& strURIPart)
 {
     if (!CheckWarmup(req)) return false;
-    const CTxMemPool* mempool = GetMemPool(req);
+    const CTxMemPool* mempool = GetMemPool(context, req);
     if (!mempool) return false;
     std::string param;
     const RetFormat rf = ParseDataFormat(param, strURIPart);
@@ -353,7 +356,7 @@ static bool rest_mempool_contents(HTTPRequest* req, const std::string& strURIPar
     }
 }
 
-static bool rest_tx(HTTPRequest* req, const std::string& strURIPart)
+static bool rest_tx(const util::Ref& context, HTTPRequest* req, const std::string& strURIPart)
 {
     if (!CheckWarmup(req))
         return false;
@@ -409,7 +412,7 @@ static bool rest_tx(HTTPRequest* req, const std::string& strURIPart)
     }
 }
 
-static bool rest_getutxos(HTTPRequest* req, const std::string& strURIPart)
+static bool rest_getutxos(const util::Ref& context, HTTPRequest* req, const std::string& strURIPart)
 {
     if (!CheckWarmup(req))
         return false;
@@ -518,7 +521,7 @@ static bool rest_getutxos(HTTPRequest* req, const std::string& strURIPart)
         };
 
         if (fCheckMemPool) {
-            const CTxMemPool* mempool = GetMemPool(req);
+            const CTxMemPool* mempool = GetMemPool(context, req);
             if (!mempool) return false;
             // use db+mempool as cache backend in case user likes to query mempool
             LOCK2(cs_main, mempool->cs);
@@ -595,7 +598,7 @@ static bool rest_getutxos(HTTPRequest* req, const std::string& strURIPart)
     }
 }
 
-static bool rest_blockhash_by_height(HTTPRequest* req,
+static bool rest_blockhash_by_height(const util::Ref& context, HTTPRequest* req,
                        const std::string& str_uri_part)
 {
     if (!CheckWarmup(req)) return false;
@@ -643,7 +646,7 @@ static bool rest_blockhash_by_height(HTTPRequest* req,
 
 static const struct {
     const char* prefix;
-    bool (*handler)(HTTPRequest* req, const std::string& strReq);
+    bool (*handler)(const util::Ref& context, HTTPRequest* req, const std::string& strReq);
 } uri_prefixes[] = {
       {"/rest/tx/", rest_tx},
       {"/rest/block/notxdetails/", rest_block_notxdetails},
@@ -656,10 +659,12 @@ static const struct {
       {"/rest/blockhashbyheight/", rest_blockhash_by_height},
 };
 
-void StartREST()
+void StartREST(const util::Ref& context)
 {
-    for (unsigned int i = 0; i < ARRAYLEN(uri_prefixes); i++)
+    for (const auto& up : uri_prefixes) {
-        RegisterHTTPHandler(uri_prefixes[i].prefix, false, uri_prefixes[i].handler);
+        auto handler = [&context, up](HTTPRequest* req, const std::string& prefix) { return up.handler(context, req, prefix); };
+        RegisterHTTPHandler(up.prefix, false, handler);
+    }
 }
 
 void InterruptREST()

src/rpc/blockchain.cpp

@@ -29,6 +29,7 @@
 #include <txdb.h>
 #include <txmempool.h>
 #include <undo.h>
+#include <util/ref.h>
 #include <util/strencodings.h>
 #include <util/system.h>
 #include <validation.h>
@@ -53,13 +54,21 @@ static Mutex cs_blockchange;
 static std::condition_variable cond_blockchange;
 static CUpdatedBlock latestblock;
 
-CTxMemPool& EnsureMemPool()
+NodeContext& EnsureNodeContext(const util::Ref& context)
 {
-    CHECK_NONFATAL(g_rpc_node);
+    if (!context.Has<NodeContext>()) {
-    if (!g_rpc_node->mempool) {
+        throw JSONRPCError(RPC_INTERNAL_ERROR, "Node context not found");
+    }
+    return context.Get<NodeContext>();
+}
+
+CTxMemPool& EnsureMemPool(const util::Ref& context)
+{
+    NodeContext& node = EnsureNodeContext(context);
+    if (!node.mempool) {
         throw JSONRPCError(RPC_CLIENT_MEMPOOL_DISABLED, "Mempool disabled or instance not found");
     }
-    return *g_rpc_node->mempool;
+    return *node.mempool;
 }
 
 /* Calculate the difficulty for a given block index.
@@ -519,7 +528,7 @@ static UniValue getrawmempool(const JSONRPCRequest& request)
     if (!request.params[0].isNull())
         fVerbose = request.params[0].get_bool();
 
-    return MempoolToJSON(EnsureMemPool(), fVerbose);
+    return MempoolToJSON(EnsureMemPool(request.context), fVerbose);
 }
 
 static UniValue getmempoolancestors(const JSONRPCRequest& request)
@@ -549,7 +558,7 @@ static UniValue getmempoolancestors(const JSONRPCRequest& request)
 
     uint256 hash = ParseHashV(request.params[0], "parameter 1");
 
-    const CTxMemPool& mempool = EnsureMemPool();
+    const CTxMemPool& mempool = EnsureMemPool(request.context);
     LOCK(mempool.cs);
 
     CTxMemPool::txiter it = mempool.mapTx.find(hash);
@@ -612,7 +621,7 @@ static UniValue getmempooldescendants(const JSONRPCRequest& request)
 
     uint256 hash = ParseHashV(request.params[0], "parameter 1");
 
-    const CTxMemPool& mempool = EnsureMemPool();
+    const CTxMemPool& mempool = EnsureMemPool(request.context);
     LOCK(mempool.cs);
 
     CTxMemPool::txiter it = mempool.mapTx.find(hash);
@@ -662,7 +671,7 @@ static UniValue getmempoolentry(const JSONRPCRequest& request)
 
     uint256 hash = ParseHashV(request.params[0], "parameter 1");
 
-    const CTxMemPool& mempool = EnsureMemPool();
+    const CTxMemPool& mempool = EnsureMemPool(request.context);
     LOCK(mempool.cs);
 
     CTxMemPool::txiter it = mempool.mapTx.find(hash);
@@ -1045,7 +1054,7 @@ UniValue gettxout(const JSONRPCRequest& request)
     CCoinsViewCache* coins_view = &::ChainstateActive().CoinsTip();
 
     if (fMempool) {
-        const CTxMemPool& mempool = EnsureMemPool();
+        const CTxMemPool& mempool = EnsureMemPool(request.context);
         LOCK(mempool.cs);
         CCoinsViewMemPool view(coins_view, mempool);
         if (!view.GetCoin(out, coin) || mempool.isSpent(out)) {
@@ -1415,7 +1424,7 @@ static UniValue getmempoolinfo(const JSONRPCRequest& request)
                 },
             }.Check(request);
 
-    return MempoolInfoToJSON(EnsureMemPool());
+    return MempoolInfoToJSON(EnsureMemPool(request.context));
 }
 
 static UniValue preciousblock(const JSONRPCRequest& request)
@@ -1934,7 +1943,7 @@ static UniValue savemempool(const JSONRPCRequest& request)
                 },
             }.Check(request);
 
-    const CTxMemPool& mempool = EnsureMemPool();
+    const CTxMemPool& mempool = EnsureMemPool(request.context);
 
     if (!mempool.IsLoaded()) {
         throw JSONRPCError(RPC_MISC_ERROR, "The mempool was not loaded yet");
@@ -2385,5 +2394,3 @@ static const CRPCCommand commands[] =
     for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++)
         t.appendCommand(commands[vcidx].name, &commands[vcidx]);
 }
-
-NodeContext* g_rpc_node = nullptr;

src/rpc/blockchain.h

@@ -18,6 +18,9 @@ class CBlockIndex;
 class CTxMemPool;
 class UniValue;
 struct NodeContext;
+namespace util {
+class Ref;
+} // namespace util
 
 static constexpr int NUM_GETBLOCKSTATS_PERCENTILES = 5;
 
@@ -47,11 +50,7 @@ UniValue blockheaderToJSON(const CBlockIndex* tip, const CBlockIndex* blockindex
 /** Used by getblockstats to get feerates at different percentiles by weight  */
 void CalculatePercentilesByWeight(CAmount result[NUM_GETBLOCKSTATS_PERCENTILES], std::vector<std::pair<CAmount, int64_t>>& scores, int64_t total_weight);
 
-//! Pointer to node state that needs to be declared as a global to be accessible
+NodeContext& EnsureNodeContext(const util::Ref& context);
-//! RPC methods. Due to limitations of the RPC framework, there's currently no
+CTxMemPool& EnsureMemPool(const util::Ref& context);
-//! direct way to pass in state to RPC methods without globals.
-extern NodeContext* g_rpc_node;
-
-CTxMemPool& EnsureMemPool();
 
 #endif

src/rpc/mining.cpp

@@ -227,7 +227,7 @@ static UniValue generatetodescriptor(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, error);
     }
 
-    const CTxMemPool& mempool = EnsureMemPool();
+    const CTxMemPool& mempool = EnsureMemPool(request.context);
 
     return generateBlocks(mempool, coinbase_script, num_blocks, max_tries);
 }
@@ -265,7 +265,7 @@ static UniValue generatetoaddress(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Error: Invalid address");
     }
 
-    const CTxMemPool& mempool = EnsureMemPool();
+    const CTxMemPool& mempool = EnsureMemPool(request.context);
 
     CScript coinbase_script = GetScriptForDestination(destination);
 
@@ -311,7 +311,7 @@ static UniValue generateblock(const JSONRPCRequest& request)
         coinbase_script = GetScriptForDestination(destination);
     }
 
-    const CTxMemPool& mempool = EnsureMemPool();
+    const CTxMemPool& mempool = EnsureMemPool(request.context);
 
     std::vector<CTransactionRef> txs;
     const auto raw_txs_or_txids = request.params[1].get_array();
@@ -403,7 +403,7 @@ static UniValue getmininginfo(const JSONRPCRequest& request)
             }.Check(request);
 
     LOCK(cs_main);
-    const CTxMemPool& mempool = EnsureMemPool();
+    const CTxMemPool& mempool = EnsureMemPool(request.context);
 
     UniValue obj(UniValue::VOBJ);
     obj.pushKV("blocks",           (int)::ChainActive().Height());
@@ -449,7 +449,7 @@ static UniValue prioritisetransaction(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Priority is no longer supported, dummy argument to prioritisetransaction must be 0.");
     }
 
-    EnsureMemPool().PrioritiseTransaction(hash, nAmount);
+    EnsureMemPool(request.context).PrioritiseTransaction(hash, nAmount);
     return true;
 }
 
@@ -635,17 +635,18 @@ static UniValue getblocktemplate(const JSONRPCRequest& request)
     if (strMode != "template")
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid mode");
 
-    if(!g_rpc_node->connman)
+    NodeContext& node = EnsureNodeContext(request.context);
+    if(!node.connman)
         throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
 
-    if (g_rpc_node->connman->GetNodeCount(CConnman::CONNECTIONS_ALL) == 0)
+    if (node.connman->GetNodeCount(CConnman::CONNECTIONS_ALL) == 0)
         throw JSONRPCError(RPC_CLIENT_NOT_CONNECTED, PACKAGE_NAME " is not connected!");
 
     if (::ChainstateActive().IsInitialBlockDownload())
         throw JSONRPCError(RPC_CLIENT_IN_INITIAL_DOWNLOAD, PACKAGE_NAME " is in initial sync and waiting for blocks...");
 
     static unsigned int nTransactionsUpdatedLast;
-    const CTxMemPool& mempool = EnsureMemPool();
+    const CTxMemPool& mempool = EnsureMemPool(request.context);
 
     if (!lpval.isNull())
     {

src/rpc/misc.cpp

@@ -15,6 +15,7 @@
 #include <script/descriptor.h>
 #include <util/check.h>
 #include <util/message.h> // For MessageSign(), MessageVerify()
+#include <util/ref.h>
 #include <util/strencodings.h>
 #include <util/system.h>
 
@@ -366,8 +367,8 @@ static UniValue setmocktime(const JSONRPCRequest& request)
     RPCTypeCheck(request.params, {UniValue::VNUM});
     int64_t time = request.params[0].get_int64();
     SetMockTime(time);
-    if (g_rpc_node) {
+    if (request.context.Has<NodeContext>()) {
-        for (const auto& chain_client : g_rpc_node->chain_clients) {
+        for (const auto& chain_client : request.context.Get<NodeContext>().chain_clients) {
             chain_client->setMockTime(time);
         }
     }
@@ -398,9 +399,10 @@ static UniValue mockscheduler(const JSONRPCRequest& request)
     }
 
     // protect against null pointer dereference
-    CHECK_NONFATAL(g_rpc_node);
+    CHECK_NONFATAL(request.context.Has<NodeContext>());
-    CHECK_NONFATAL(g_rpc_node->scheduler);
+    NodeContext& node = request.context.Get<NodeContext>();
-    g_rpc_node->scheduler->MockForward(std::chrono::seconds(delta_seconds));
+    CHECK_NONFATAL(node.scheduler);
+    node.scheduler->MockForward(std::chrono::seconds(delta_seconds));
 
     return NullUniValue;
 }

src/rpc/net.cpp

@@ -42,10 +42,11 @@ static UniValue getconnectioncount(const JSONRPCRequest& request)
                 },
             }.Check(request);
 
-    if(!g_rpc_node->connman)
+    NodeContext& node = EnsureNodeContext(request.context);
+    if(!node.connman)
         throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
 
-    return (int)g_rpc_node->connman->GetNodeCount(CConnman::CONNECTIONS_ALL);
+    return (int)node.connman->GetNodeCount(CConnman::CONNECTIONS_ALL);
 }
 
 static UniValue ping(const JSONRPCRequest& request)
@@ -62,11 +63,12 @@ static UniValue ping(const JSONRPCRequest& request)
                 },
             }.Check(request);
 
-    if(!g_rpc_node->connman)
+    NodeContext& node = EnsureNodeContext(request.context);
+    if(!node.connman)
         throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
 
     // Request that each node send a ping during next message processing pass
-    g_rpc_node->connman->ForEachNode([](CNode* pnode) {
+    node.connman->ForEachNode([](CNode* pnode) {
         pnode->fPingQueued = true;
     });
     return NullUniValue;
@@ -139,11 +141,12 @@ static UniValue getpeerinfo(const JSONRPCRequest& request)
                 },
             }.Check(request);
 
-    if(!g_rpc_node->connman)
+    NodeContext& node = EnsureNodeContext(request.context);
+    if(!node.connman)
         throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
 
     std::vector<CNodeStats> vstats;
-    g_rpc_node->connman->GetNodeStats(vstats);
+    node.connman->GetNodeStats(vstats);
 
     UniValue ret(UniValue::VARR);
 
@@ -248,7 +251,8 @@ static UniValue addnode(const JSONRPCRequest& request)
                 },
             }.ToString());
 
-    if(!g_rpc_node->connman)
+    NodeContext& node = EnsureNodeContext(request.context);
+    if(!node.connman)
         throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
 
     std::string strNode = request.params[0].get_str();
@@ -256,18 +260,18 @@ static UniValue addnode(const JSONRPCRequest& request)
     if (strCommand == "onetry")
     {
         CAddress addr;
-        g_rpc_node->connman->OpenNetworkConnection(addr, false, nullptr, strNode.c_str(), false, false, true);
+        node.connman->OpenNetworkConnection(addr, false, nullptr, strNode.c_str(), false, false, true);
         return NullUniValue;
     }
 
     if (strCommand == "add")
     {
-        if(!g_rpc_node->connman->AddNode(strNode))
+        if(!node.connman->AddNode(strNode))
             throw JSONRPCError(RPC_CLIENT_NODE_ALREADY_ADDED, "Error: Node already added");
     }
     else if(strCommand == "remove")
     {
-        if(!g_rpc_node->connman->RemoveAddedNode(strNode))
+        if(!node.connman->RemoveAddedNode(strNode))
             throw JSONRPCError(RPC_CLIENT_NODE_NOT_ADDED, "Error: Node has not been added.");
     }
 
@@ -293,7 +297,8 @@ static UniValue disconnectnode(const JSONRPCRequest& request)
                 },
             }.Check(request);
 
-    if(!g_rpc_node->connman)
+    NodeContext& node = EnsureNodeContext(request.context);
+    if(!node.connman)
         throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
 
     bool success;
@@ -302,11 +307,11 @@ static UniValue disconnectnode(const JSONRPCRequest& request)
 
     if (!address_arg.isNull() && id_arg.isNull()) {
         /* handle disconnect-by-address */
-        success = g_rpc_node->connman->DisconnectNode(address_arg.get_str());
+        success = node.connman->DisconnectNode(address_arg.get_str());
     } else if (!id_arg.isNull() && (address_arg.isNull() || (address_arg.isStr() && address_arg.get_str().empty()))) {
         /* handle disconnect-by-id */
         NodeId nodeid = (NodeId) id_arg.get_int64();
-        success = g_rpc_node->connman->DisconnectNode(nodeid);
+        success = node.connman->DisconnectNode(nodeid);
     } else {
         throw JSONRPCError(RPC_INVALID_PARAMS, "Only one of address and nodeid should be provided.");
     }
@@ -350,10 +355,11 @@ static UniValue getaddednodeinfo(const JSONRPCRequest& request)
                 },
             }.Check(request);
 
-    if(!g_rpc_node->connman)
+    NodeContext& node = EnsureNodeContext(request.context);
+    if(!node.connman)
         throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
 
-    std::vector<AddedNodeInfo> vInfo = g_rpc_node->connman->GetAddedNodeInfo();
+    std::vector<AddedNodeInfo> vInfo = node.connman->GetAddedNodeInfo();
 
     if (!request.params[0].isNull()) {
         bool found = false;
@@ -417,21 +423,22 @@ static UniValue getnettotals(const JSONRPCRequest& request)
             + HelpExampleRpc("getnettotals", "")
                 },
             }.Check(request);
-    if(!g_rpc_node->connman)
+    NodeContext& node = EnsureNodeContext(request.context);
+    if(!node.connman)
         throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
 
     UniValue obj(UniValue::VOBJ);
-    obj.pushKV("totalbytesrecv", g_rpc_node->connman->GetTotalBytesRecv());
+    obj.pushKV("totalbytesrecv", node.connman->GetTotalBytesRecv());
-    obj.pushKV("totalbytessent", g_rpc_node->connman->GetTotalBytesSent());
+    obj.pushKV("totalbytessent", node.connman->GetTotalBytesSent());
     obj.pushKV("timemillis", GetTimeMillis());
 
     UniValue outboundLimit(UniValue::VOBJ);
-    outboundLimit.pushKV("timeframe", g_rpc_node->connman->GetMaxOutboundTimeframe());
+    outboundLimit.pushKV("timeframe", node.connman->GetMaxOutboundTimeframe());
-    outboundLimit.pushKV("target", g_rpc_node->connman->GetMaxOutboundTarget());
+    outboundLimit.pushKV("target", node.connman->GetMaxOutboundTarget());
-    outboundLimit.pushKV("target_reached", g_rpc_node->connman->OutboundTargetReached(false));
+    outboundLimit.pushKV("target_reached", node.connman->OutboundTargetReached(false));
-    outboundLimit.pushKV("serve_historical_blocks", !g_rpc_node->connman->OutboundTargetReached(true));
+    outboundLimit.pushKV("serve_historical_blocks", !node.connman->OutboundTargetReached(true));
-    outboundLimit.pushKV("bytes_left_in_cycle", g_rpc_node->connman->GetOutboundTargetBytesLeft());
+    outboundLimit.pushKV("bytes_left_in_cycle", node.connman->GetOutboundTargetBytesLeft());
-    outboundLimit.pushKV("time_left_in_cycle", g_rpc_node->connman->GetMaxOutboundTimeLeftInCycle());
+    outboundLimit.pushKV("time_left_in_cycle", node.connman->GetMaxOutboundTimeLeftInCycle());
     obj.pushKV("uploadtarget", outboundLimit);
     return obj;
 }
@@ -513,16 +520,17 @@ static UniValue getnetworkinfo(const JSONRPCRequest& request)
     obj.pushKV("version",       CLIENT_VERSION);
     obj.pushKV("subversion",    strSubVersion);
     obj.pushKV("protocolversion",PROTOCOL_VERSION);
-    if (g_rpc_node->connman) {
+    NodeContext& node = EnsureNodeContext(request.context);
-        ServiceFlags services = g_rpc_node->connman->GetLocalServices();
+    if (node.connman) {
+        ServiceFlags services = node.connman->GetLocalServices();
         obj.pushKV("localservices", strprintf("%016x", services));
         obj.pushKV("localservicesnames", GetServicesNames(services));
     }
     obj.pushKV("localrelay", g_relay_txes);
     obj.pushKV("timeoffset",    GetTimeOffset());
-    if (g_rpc_node->connman) {
+    if (node.connman) {
-        obj.pushKV("networkactive", g_rpc_node->connman->GetNetworkActive());
+        obj.pushKV("networkactive", node.connman->GetNetworkActive());
-        obj.pushKV("connections",   (int)g_rpc_node->connman->GetNodeCount(CConnman::CONNECTIONS_ALL));
+        obj.pushKV("connections",   (int)node.connman->GetNodeCount(CConnman::CONNECTIONS_ALL));
     }
     obj.pushKV("networks",      GetNetworksInfo());
     obj.pushKV("relayfee",      ValueFromAmount(::minRelayTxFee.GetFeePerK()));
@@ -567,7 +575,8 @@ static UniValue setban(const JSONRPCRequest& request)
     if (request.fHelp || !help.IsValidNumArgs(request.params.size()) || (strCommand != "add" && strCommand != "remove")) {
         throw std::runtime_error(help.ToString());
     }
-    if (!g_rpc_node->banman) {
+    NodeContext& node = EnsureNodeContext(request.context);
+    if (!node.banman) {
         throw JSONRPCError(RPC_DATABASE_ERROR, "Error: Ban database not loaded");
     }
 
@@ -591,7 +600,7 @@ static UniValue setban(const JSONRPCRequest& request)
 
     if (strCommand == "add")
     {
-        if (isSubnet ? g_rpc_node->banman->IsBanned(subNet) : g_rpc_node->banman->IsBanned(netAddr)) {
+        if (isSubnet ? node.banman->IsBanned(subNet) : node.banman->IsBanned(netAddr)) {
             throw JSONRPCError(RPC_CLIENT_NODE_ALREADY_ADDED, "Error: IP/Subnet already banned");
         }
 
@@ -604,20 +613,20 @@ static UniValue setban(const JSONRPCRequest& request)
             absolute = true;
 
         if (isSubnet) {
-            g_rpc_node->banman->Ban(subNet, BanReasonManuallyAdded, banTime, absolute);
+            node.banman->Ban(subNet, BanReasonManuallyAdded, banTime, absolute);
-            if (g_rpc_node->connman) {
+            if (node.connman) {
-                g_rpc_node->connman->DisconnectNode(subNet);
+                node.connman->DisconnectNode(subNet);
             }
         } else {
-            g_rpc_node->banman->Ban(netAddr, BanReasonManuallyAdded, banTime, absolute);
+            node.banman->Ban(netAddr, BanReasonManuallyAdded, banTime, absolute);
-            if (g_rpc_node->connman) {
+            if (node.connman) {
-                g_rpc_node->connman->DisconnectNode(netAddr);
+                node.connman->DisconnectNode(netAddr);
             }
         }
     }
     else if(strCommand == "remove")
     {
-        if (!( isSubnet ? g_rpc_node->banman->Unban(subNet) : g_rpc_node->banman->Unban(netAddr) )) {
+        if (!( isSubnet ? node.banman->Unban(subNet) : node.banman->Unban(netAddr) )) {
             throw JSONRPCError(RPC_CLIENT_INVALID_IP_OR_SUBNET, "Error: Unban failed. Requested address/subnet was not previously banned.");
         }
     }
@@ -645,12 +654,13 @@ static UniValue listbanned(const JSONRPCRequest& request)
                 },
             }.Check(request);
 
-    if(!g_rpc_node->banman) {
+    NodeContext& node = EnsureNodeContext(request.context);
+    if(!node.banman) {
         throw JSONRPCError(RPC_DATABASE_ERROR, "Error: Ban database not loaded");
     }
 
     banmap_t banMap;
-    g_rpc_node->banman->GetBanned(banMap);
+    node.banman->GetBanned(banMap);
 
     UniValue bannedAddresses(UniValue::VARR);
     for (const auto& entry : banMap)
@@ -679,11 +689,12 @@ static UniValue clearbanned(const JSONRPCRequest& request)
                             + HelpExampleRpc("clearbanned", "")
                 },
             }.Check(request);
-    if (!g_rpc_node->banman) {
+    NodeContext& node = EnsureNodeContext(request.context);
+    if (!node.banman) {
         throw JSONRPCError(RPC_DATABASE_ERROR, "Error: Ban database not loaded");
     }
 
-    g_rpc_node->banman->ClearBanned();
+    node.banman->ClearBanned();
 
     return NullUniValue;
 }
@@ -699,13 +710,14 @@ static UniValue setnetworkactive(const JSONRPCRequest& request)
                 RPCExamples{""},
             }.Check(request);
 
-    if (!g_rpc_node->connman) {
+    NodeContext& node = EnsureNodeContext(request.context);
+    if (!node.connman) {
         throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
     }
 
-    g_rpc_node->connman->SetNetworkActive(request.params[0].get_bool());
+    node.connman->SetNetworkActive(request.params[0].get_bool());
 
-    return g_rpc_node->connman->GetNetworkActive();
+    return node.connman->GetNetworkActive();
 }
 
 static UniValue getnodeaddresses(const JSONRPCRequest& request)
@@ -732,7 +744,8 @@ static UniValue getnodeaddresses(const JSONRPCRequest& request)
             + HelpExampleRpc("getnodeaddresses", "8")
                 },
             }.Check(request);
-    if (!g_rpc_node->connman) {
+    NodeContext& node = EnsureNodeContext(request.context);
+    if (!node.connman) {
         throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
     }
 
@@ -744,7 +757,7 @@ static UniValue getnodeaddresses(const JSONRPCRequest& request)
         }
     }
     // returns a shuffled list of CAddress
-    std::vector<CAddress> vAddr = g_rpc_node->connman->GetAddresses();
+    std::vector<CAddress> vAddr = node.connman->GetAddresses();
     UniValue ret(UniValue::VARR);
 
     int address_return_count = std::min<int>(count, vAddr.size());

src/rpc/rawtransaction.cpp

@@ -653,7 +653,7 @@ static UniValue combinerawtransaction(const JSONRPCRequest& request)
     CCoinsView viewDummy;
     CCoinsViewCache view(&viewDummy);
     {
-        const CTxMemPool& mempool = EnsureMemPool();
+        const CTxMemPool& mempool = EnsureMemPool(request.context);
         LOCK(cs_main);
         LOCK(mempool.cs);
         CCoinsViewCache &viewChain = ::ChainstateActive().CoinsTip();
@@ -778,7 +778,8 @@ static UniValue signrawtransactionwithkey(const JSONRPCRequest& request)
     for (const CTxIn& txin : mtx.vin) {
         coins[txin.prevout]; // Create empty map entry keyed by prevout.
     }
-    FindCoins(*g_rpc_node, coins);
+    NodeContext& node = EnsureNodeContext(request.context);
+    FindCoins(node, coins);
 
     // Parse the prevtxs array
     ParsePrevouts(request.params[2], &keystore, coins);
@@ -837,7 +838,8 @@ static UniValue sendrawtransaction(const JSONRPCRequest& request)
 
     std::string err_string;
     AssertLockNotHeld(cs_main);
-    const TransactionError err = BroadcastTransaction(*g_rpc_node, tx, err_string, max_raw_tx_fee, /*relay*/ true, /*wait_callback*/ true);
+    NodeContext& node = EnsureNodeContext(request.context);
+    const TransactionError err = BroadcastTransaction(node, tx, err_string, max_raw_tx_fee, /*relay*/ true, /*wait_callback*/ true);
     if (TransactionError::OK != err) {
         throw JSONRPCTransactionError(err, err_string);
     }
@@ -904,7 +906,7 @@ static UniValue testmempoolaccept(const JSONRPCRequest& request)
                                              DEFAULT_MAX_RAW_TX_FEE_RATE :
                                              CFeeRate(AmountFromValue(request.params[1]));
 
-    CTxMemPool& mempool = EnsureMemPool();
+    CTxMemPool& mempool = EnsureMemPool(request.context);
     int64_t virtual_size = GetVirtualTransactionSize(*tx);
     CAmount max_raw_tx_fee = max_raw_tx_fee_rate.GetFee(virtual_size);
 
@@ -1555,7 +1557,7 @@ UniValue utxoupdatepsbt(const JSONRPCRequest& request)
     CCoinsView viewDummy;
     CCoinsViewCache view(&viewDummy);
     {
-        const CTxMemPool& mempool = EnsureMemPool();
+        const CTxMemPool& mempool = EnsureMemPool(request.context);
         LOCK2(cs_main, mempool.cs);
         CCoinsViewCache &viewChain = ::ChainstateActive().CoinsTip();
         CCoinsViewMemPool viewMempool(&viewChain, mempool);

src/rpc/request.h

@@ -10,6 +10,10 @@
 
 #include <univalue.h>
 
+namespace util {
+class Ref;
+} // namespace util
+
 UniValue JSONRPCRequestObj(const std::string& strMethod, const UniValue& params, const UniValue& id);
 UniValue JSONRPCReplyObj(const UniValue& result, const UniValue& error, const UniValue& id);
 std::string JSONRPCReply(const UniValue& result, const UniValue& error, const UniValue& id);
@@ -34,8 +38,9 @@ public:
     std::string URI;
     std::string authUser;
     std::string peerAddr;
+    const util::Ref& context;
 
-    JSONRPCRequest() : id(NullUniValue), params(NullUniValue), fHelp(false) {}
+    JSONRPCRequest(const util::Ref& context) : id(NullUniValue), params(NullUniValue), fHelp(false), context(context) {}
     void parse(const UniValue& valRequest);
 };
 

src/test/ref_tests.cpp

@@ -0,0 +1,33 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <util/ref.h>
+
+#include <boost/test/unit_test.hpp>
+
+BOOST_AUTO_TEST_SUITE(ref_tests)
+
+BOOST_AUTO_TEST_CASE(ref_test)
+{
+    util::Ref ref;
+    BOOST_CHECK(!ref.Has<int>());
+    BOOST_CHECK_THROW(ref.Get<int>(), NonFatalCheckError);
+    int value = 5;
+    ref.Set(value);
+    BOOST_CHECK(ref.Has<int>());
+    BOOST_CHECK_EQUAL(ref.Get<int>(), 5);
+    ++ref.Get<int>();
+    BOOST_CHECK_EQUAL(ref.Get<int>(), 6);
+    BOOST_CHECK_EQUAL(value, 6);
+    ++value;
+    BOOST_CHECK_EQUAL(value, 7);
+    BOOST_CHECK_EQUAL(ref.Get<int>(), 7);
+    BOOST_CHECK(!ref.Has<bool>());
+    BOOST_CHECK_THROW(ref.Get<bool>(), NonFatalCheckError);
+    ref.Clear();
+    BOOST_CHECK(!ref.Has<int>());
+    BOOST_CHECK_THROW(ref.Get<int>(), NonFatalCheckError);
+}
+
+BOOST_AUTO_TEST_SUITE_END()

src/test/rpc_tests.cpp

@@ -10,6 +10,7 @@
 #include <interfaces/chain.h>
 #include <node/context.h>
 #include <test/util/setup_common.h>
+#include <util/ref.h>
 #include <util/time.h>
 
 #include <boost/algorithm/string.hpp>
@@ -19,13 +20,20 @@
 
 #include <rpc/blockchain.h>
 
-UniValue CallRPC(std::string args)
+class RPCTestingSetup : public TestingSetup
+{
+public:
+    UniValue CallRPC(std::string args);
+};
+
+UniValue RPCTestingSetup::CallRPC(std::string args)
 {
     std::vector<std::string> vArgs;
     boost::split(vArgs, args, boost::is_any_of(" \t"));
     std::string strMethod = vArgs[0];
     vArgs.erase(vArgs.begin());
-    JSONRPCRequest request;
+    util::Ref context{m_node};
+    JSONRPCRequest request(context);
     request.strMethod = strMethod;
     request.params = RPCConvertValues(strMethod, vArgs);
     request.fHelp = false;
@@ -40,7 +48,7 @@ UniValue CallRPC(std::string args)
 }
 
 
-BOOST_FIXTURE_TEST_SUITE(rpc_tests, TestingSetup)
+BOOST_FIXTURE_TEST_SUITE(rpc_tests, RPCTestingSetup)
 
 BOOST_AUTO_TEST_CASE(rpc_rawparams)
 {

src/test/util/setup_common.cpp

@@ -123,7 +123,6 @@ TestingSetup::TestingSetup(const std::string& chainName, const std::vector<const
     const CChainParams& chainparams = Params();
     // Ideally we'd move all the RPC tests to the functional testing framework
     // instead of unit tests, but for now we need these here.
-    g_rpc_node = &m_node;
     RegisterAllCoreRPCCommands(tableRPC);
 
     m_node.scheduler = MakeUnique<CScheduler>();
@@ -131,7 +130,7 @@ TestingSetup::TestingSetup(const std::string& chainName, const std::vector<const
     // We have to run a scheduler thread to prevent ActivateBestChain
     // from blocking due to queue overrun.
     threadGroup.create_thread([&]{ m_node.scheduler->serviceQueue(); });
-    GetMainSignals().RegisterBackgroundSignalScheduler(*g_rpc_node->scheduler);
+    GetMainSignals().RegisterBackgroundSignalScheduler(*m_node.scheduler);
 
     pblocktree.reset(new CBlockTreeDB(1 << 20, true));
 
@@ -176,7 +175,6 @@ TestingSetup::~TestingSetup()
     threadGroup.join_all();
     GetMainSignals().FlushBackgroundCallbacks();
     GetMainSignals().UnregisterBackgroundSignalScheduler();
-    g_rpc_node = nullptr;
     m_node.connman.reset();
     m_node.banman.reset();
     m_node.args = nullptr;

src/util/check.h

@@ -5,6 +5,10 @@
 #ifndef BITCOIN_UTIL_CHECK_H
 #define BITCOIN_UTIL_CHECK_H
 
+#if defined(HAVE_CONFIG_H)
+#include <config/bitcoin-config.h>
+#endif
+
 #include <tinyformat.h>
 
 #include <stdexcept>

src/util/ref.h

@@ -0,0 +1,38 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_REF_H
+#define BITCOIN_UTIL_REF_H
+
+#include <util/check.h>
+
+#include <typeindex>
+
+namespace util {
+
+/**
+ * Type-safe dynamic reference.
+ *
+ * This implements a small subset of the functionality in C++17's std::any
+ * class, and can be dropped when the project updates to C++17
+ * (https://github.com/bitcoin/bitcoin/issues/16684)
+ */
+class Ref
+{
+public:
+    Ref() = default;
+    template<typename T> Ref(T& value) { Set(value); }
+    template<typename T> T& Get() const { CHECK_NONFATAL(Has<T>()); return *static_cast<T*>(m_value); }
+    template<typename T> void Set(T& value) { m_value = &value; m_type = std::type_index(typeid(T)); }
+    template<typename T> bool Has() const { return m_value && m_type == std::type_index(typeid(T)); }
+    void Clear() { m_value = nullptr; m_type = std::type_index(typeid(void)); }
+
+private:
+    void* m_value = nullptr;
+    std::type_index m_type = std::type_index(typeid(void));
+};
+
+} // namespace util
+
+#endif // BITCOIN_UTIL_REF_H

src/wallet/test/wallet_tests.cpp

@@ -15,6 +15,7 @@
 #include <rpc/server.h>
 #include <test/util/logging.h>
 #include <test/util/setup_common.h>
+#include <util/ref.h>
 #include <util/translation.h>
 #include <validation.h>
 #include <wallet/coincontrol.h>
@@ -208,7 +209,8 @@ BOOST_FIXTURE_TEST_CASE(importmulti_rescan, TestChain100Setup)
         key.pushKV("timestamp", newTip->GetBlockTimeMax() + TIMESTAMP_WINDOW + 1);
         key.pushKV("internal", UniValue(true));
         keys.push_back(key);
-        JSONRPCRequest request;
+        util::Ref context;
+        JSONRPCRequest request(context);
         request.params.setArray();
         request.params.push_back(keys);
 
@@ -262,7 +264,8 @@ BOOST_FIXTURE_TEST_CASE(importwallet_rescan, TestChain100Setup)
             AddWallet(wallet);
             wallet->SetLastBlockProcessed(::ChainActive().Height(), ::ChainActive().Tip()->GetBlockHash());
         }
-        JSONRPCRequest request;
+        util::Ref context;
+        JSONRPCRequest request(context);
         request.params.setArray();
         request.params.push_back(backup_file);
 
@@ -277,7 +280,8 @@ BOOST_FIXTURE_TEST_CASE(importwallet_rescan, TestChain100Setup)
         LOCK(wallet->cs_wallet);
         wallet->SetupLegacyScriptPubKeyMan();
 
-        JSONRPCRequest request;
+        util::Ref context;
+        JSONRPCRequest request(context);
         request.params.setArray();
         request.params.push_back(backup_file);
         AddWallet(wallet);