Incrementally update sv2 block template

Co-Authored-By: Fi3

src/init.cpp

@@ -654,6 +654,8 @@ void SetupServerArgs(ArgsManager& argsman)
     argsman.AddArg("-blockmintxfee=<amt>", strprintf("Set lowest fee rate (in %s/kvB) for transactions to be included in block creation. (default: %s)", CURRENCY_UNIT, FormatMoney(DEFAULT_BLOCK_MIN_TX_FEE)), ArgsManager::ALLOW_ANY, OptionsCategory::BLOCK_CREATION);
     argsman.AddArg("-blockversion=<n>", "Override block version to test forking scenarios", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::BLOCK_CREATION);
     argsman.AddArg("-sv2", "Bitcoind will act as a Stratum v2 Template Provider (default: false)", ArgsManager::ALLOW_ANY, OptionsCategory::BLOCK_CREATION);
+    argsman.AddArg("-sv2interval", strprintf("Template Provider block template update interval (default: %d seconds)", DEFAULT_SV2_INTERVAL), ArgsManager::ALLOW_ANY, OptionsCategory::BLOCK_CREATION);
+    argsman.AddArg("-sv2feedelta", strprintf("Minimum fee delta for Template Provider to send update upstream (default: %d sat)", DEFAULT_SV2_INTERVAL), ArgsManager::ALLOW_ANY, OptionsCategory::BLOCK_CREATION);
 
     argsman.AddArg("-rest", strprintf("Accept public REST requests (default: %u)", DEFAULT_REST_ENABLE), ArgsManager::ALLOW_ANY, OptionsCategory::RPC);
     argsman.AddArg("-rpcallowip=<ip>", "Allow JSON-RPC connections from specified source. Valid values for <ip> are a single IP (e.g. 1.2.3.4), a network/netmask (e.g. 1.2.3.4/255.255.255.0), a network/CIDR (e.g. 1.2.3.4/24), all ipv4 (0.0.0.0/0), or all ipv6 (::/0). This option can be specified multiple times", ArgsManager::ALLOW_ANY, OptionsCategory::RPC);
@@ -1025,6 +1027,10 @@ bool AppInitParameterInteraction(const ArgsManager& args)
 
     nBytesPerSigOp = args.GetIntArg("-bytespersigop", nBytesPerSigOp);
 
+    if (args.GetIntArg("-sv2interval", DEFAULT_SV2_INTERVAL) < 1) {
+        return InitError(Untranslated("-sv2interval must be at least one second"));
+    }
+
     if (!g_wallet_init_interface.ParameterInteraction()) return false;
 
     // Option to startup with mocktime set (used for regression testing):

src/node/miner.h

@@ -27,6 +27,11 @@ class CScript;
 class Chainstate;
 class ChainstateManager;
 
+/** Default for -sv2interval **/
+static constexpr unsigned int DEFAULT_SV2_INTERVAL{30};
+/** Default for -sv2feedelta */
+static constexpr unsigned int DEFAULT_SV2_FEE_DELTA{1000};
+
 namespace Consensus { struct Params; };
 
 namespace node {

src/node/sv2_template_provider.cpp

@@ -1,5 +1,6 @@
 #include <node/sv2_template_provider.h>
 
+#include <common/args.h>
 #include <consensus/merkle.h>
 #include <txmempool.h>
 #include <util/thread.h>
@@ -52,6 +53,7 @@ bool Sv2TemplateProvider::Start(const Sv2TemplateProviderOptions& options)
 
 void Sv2TemplateProvider::Init(const Sv2TemplateProviderOptions& options)
 {
+    m_minimum_fee_delta = gArgs.GetIntArg("-sv2feedelta", DEFAULT_SV2_FEE_DELTA);
     m_port = options.port;
     m_protocol_version = options.protocol_version;
     m_optional_features = options.optional_features;
@@ -114,6 +116,27 @@ std::shared_ptr<Sock> Sv2TemplateProvider::BindListenPort(uint16_t port) const
 
     return sock;
 }
+class Timer {
+private:
+    std::chrono::seconds m_interval;
+    std::chrono::steady_clock::time_point m_last_triggered;
+
+public:
+    Timer() {
+        m_interval = std::chrono::seconds(gArgs.GetIntArg("-sv2interval", DEFAULT_SV2_INTERVAL));
+        // Initialize the timer to a time point far in the past
+        m_last_triggered = std::chrono::steady_clock::now() - std::chrono::hours(1);
+    }
+
+    bool trigger() {
+        auto now = std::chrono::steady_clock::now();
+        if (now - m_last_triggered >= m_interval) {
+            m_last_triggered = now;
+            return true;
+        }
+        return false;
+    }
+};
 
 void Sv2TemplateProvider::DisconnectFlagged()
 {
@@ -126,6 +149,10 @@ void Sv2TemplateProvider::DisconnectFlagged()
 
 void Sv2TemplateProvider::ThreadSv2Handler()
 {
+    Timer timer;
+    unsigned int mempool_last_update = 0;
+    unsigned int template_last_update = 0;
+
     while (!m_flag_interrupt_sv2) {
         if (m_chainman.IsInitialBlockDownload()) {
             m_interrupt_sv2.sleep_for(std::chrono::milliseconds(100));
@@ -159,6 +186,11 @@ void Sv2TemplateProvider::ThreadSv2Handler()
             return false;
         }();
 
+
+        /** TODO: only look for mempool updates that (likely) impact the next block.
+         *        See `doc/stratum-v2.md#mempool-monitoring`
+         */
+        mempool_last_update = m_mempool.GetTransactionsUpdated();
         bool should_make_template = false;
 
         if (best_block_changed) {
@@ -167,8 +199,15 @@ void Sv2TemplateProvider::ThreadSv2Handler()
             BlockCache block_cache;
             m_block_cache.swap(block_cache);
 
+            for (auto& client : m_sv2_clients) {
+                client->m_latest_submitted_template_fees = 0;
+            }
+
             // Build a new best template, best prev hash and update the block cache.
             should_make_template = true;
+            template_last_update = mempool_last_update;
+        } else if (timer.trigger() && mempool_last_update > template_last_update) {
+            should_make_template = true;
         }
 
         if (should_make_template) {
@@ -348,6 +387,15 @@ bool Sv2TemplateProvider::SendWork(Sv2Client& client, bool send_new_prevhash)
     ++m_template_id;
     auto new_work_set = BuildNewWorkSet(/*future_template=*/send_new_prevhash, client.m_coinbase_tx_outputs_size);
 
+    // Do not submit new template if the fee increase is insufficient:
+    CAmount fees = 0;
+    for (CAmount fee : new_work_set.block_template->vTxFees) {
+        // Skip coinbase
+        if (fee < 0) continue;
+        fees += fee;
+    }
+    if (!send_new_prevhash && client.m_latest_submitted_template_fees + m_minimum_fee_delta > fees) return true;
+
     m_block_cache.insert({m_template_id, std::move(new_work_set.block_template)});
 
     LogPrintLevel(BCLog::SV2, BCLog::Level::Debug, "Send 0x71 NewTemplate\n");
@@ -358,6 +406,8 @@ bool Sv2TemplateProvider::SendWork(Sv2Client& client, bool send_new_prevhash)
         client.m_send_messages.emplace_back(Sv2NetMsg{new_work_set.prev_hash});
     }
 
+    client.m_latest_submitted_template_fees = fees;
+
     return true;
 }
 

src/node/sv2_template_provider.h

@@ -50,6 +50,12 @@ struct Sv2Client
 
     explicit Sv2Client(std::shared_ptr<Sock> sock, std::unique_ptr<Sv2Transport> transport) :
                        m_sock{std::move(sock)}, m_transport{std::move(transport)} {};
+
+    /**
+     * Fees in sat paid by the last submitted template
+     */
+    CAmount m_latest_submitted_template_fees = 0;
+
 };
 
 struct Sv2TemplateProviderOptions
@@ -101,6 +107,12 @@ class Sv2TemplateProvider
      */
     std::shared_ptr<Sock> m_listening_socket;
 
+    /**
+    * Minimum fee delta required before submitting an updated template.
+    * This may be negative.
+    */
+    int m_minimum_fee_delta;
+
     /**
      * The main thread for the template provider.
      */