Merge #14982: rpc: Add getrpcinfo command

a0ac15459a doc: Add getrpcinfo release notes (João Barbosa)
251a91c1bf qa: Add tests for getrpcinfo (João Barbosa)
d0730f5ce4 rpc: Add getrpcinfo command (João Barbosa)
068a8fc05f rpc: Track active commands (João Barbosa)
bf4383277d rpc: Remove unused PreCommand signal (João Barbosa)

Pull request description:

  The new `getrpcinfo` command exposes details of the RPC interface. The details can be configuration properties or runtime values/stats.

  This can be particular useful to coordinate concurrent functional tests (see #14958 from where this was extracted).

Tree-SHA512: 7292cb6087f4c429973d991aa2b53ffa1327d5a213df7d6ba5fc69b01b2e1a411f6d1609fed9234896293317dab05f65064da48b8f2b4a998eba532591d31882

doc/release-notes-14982.md

@@ -0,0 +1,5 @@
+New RPCs
+--------
+
+- The RPC `getrpcinfo` returns runtime details of the RPC server. At the moment
+  it returns the active commands and the corresponding execution time.

src/rpc/server.cpp

@@ -31,11 +31,39 @@ static RPCTimerInterface* timerInterface = nullptr;
 /* Map of name to timer. */
 static std::map<std::string, std::unique_ptr<RPCTimerBase> > deadlineTimers;
 
+struct RPCCommandExecutionInfo
+{
+    std::string method;
+    int64_t start;
+};
+
+struct RPCServerInfo
+{
+    Mutex mutex;
+    std::list<RPCCommandExecutionInfo> active_commands GUARDED_BY(mutex);
+};
+
+static RPCServerInfo g_rpc_server_info;
+
+struct RPCCommandExecution
+{
+    std::list<RPCCommandExecutionInfo>::iterator it;
+    explicit RPCCommandExecution(const std::string& method)
+    {
+        LOCK(g_rpc_server_info.mutex);
+        it = g_rpc_server_info.active_commands.insert(g_rpc_server_info.active_commands.cend(), {method, GetTimeMicros()});
+    }
+    ~RPCCommandExecution()
+    {
+        LOCK(g_rpc_server_info.mutex);
+        g_rpc_server_info.active_commands.erase(it);
+    }
+};
+
 static struct CRPCSignals
 {
     boost::signals2::signal<void ()> Started;
     boost::signals2::signal<void ()> Stopped;
-    boost::signals2::signal<void (const CRPCCommand&)> PreCommand;
 } g_rpcSignals;
 
 void RPCServer::OnStarted(std::function<void ()> slot)
@@ -254,11 +282,37 @@ static UniValue uptime(const JSONRPCRequest& jsonRequest)
     return GetTime() - GetStartupTime();
 }
 
+static UniValue getrpcinfo(const JSONRPCRequest& request)
+{
+    if (request.fHelp || request.params.size() > 0) {
+        throw std::runtime_error(
+            RPCHelpMan{"getrpcinfo",
+                "\nReturns details of the RPC server.\n", {}}
+                .ToString()
+        );
+    }
+
+    LOCK(g_rpc_server_info.mutex);
+    UniValue active_commands(UniValue::VARR);
+    for (const RPCCommandExecutionInfo& info : g_rpc_server_info.active_commands) {
+        UniValue entry(UniValue::VOBJ);
+        entry.pushKV("method", info.method);
+        entry.pushKV("duration", GetTimeMicros() - info.start);
+        active_commands.push_back(entry);
+    }
+
+    UniValue result(UniValue::VOBJ);
+    result.pushKV("active_commands", active_commands);
+
+    return result;
+}
+
 // clang-format off
 static const CRPCCommand vRPCCommands[] =
 { //  category              name                      actor (function)         argNames
   //  --------------------- ------------------------  -----------------------  ----------
     /* Overall control/query calls */
+    { "control",            "getrpcinfo",             &getrpcinfo,             {}  },
     { "control",            "help",                   &help,                   {"command"}  },
     { "control",            "stop",                   &stop,                   {"wait"}  },
     { "control",            "uptime",                 &uptime,                 {}  },
@@ -483,10 +537,9 @@ UniValue CRPCTable::execute(const JSONRPCRequest &request) const
     if (!pcmd)
         throw JSONRPCError(RPC_METHOD_NOT_FOUND, "Method not found");
 
-    g_rpcSignals.PreCommand(*pcmd);
-
     try
     {
+        RPCCommandExecution execution(request.strMethod);
         // Execute, convert arguments to array if necessary
         if (request.params.isObject()) {
             return pcmd->actor(transformNamedArguments(request, pcmd->argNames));

test/functional/interface_rpc.py

@@ -5,13 +5,23 @@
 """Tests some generic aspects of the RPC interface."""
 
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal
+from test_framework.util import assert_equal, assert_greater_than_or_equal
 
 class RPCInterfaceTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 1
         self.setup_clean_chain = True
 
+    def test_getrpcinfo(self):
+        self.log.info("Testing getrpcinfo...")
+
+        info = self.nodes[0].getrpcinfo()
+        assert_equal(len(info['active_commands']), 1)
+
+        command = info['active_commands'][0]
+        assert_equal(command['method'], 'getrpcinfo')
+        assert_greater_than_or_equal(command['duration'], 0)
+
     def test_batch_request(self):
         self.log.info("Testing basic JSON-RPC batch request...")
 
@@ -39,6 +49,7 @@ class RPCInterfaceTest(BitcoinTestFramework):
         assert result_by_id[3]['result'] is not None
 
     def run_test(self):
+        self.test_getrpcinfo()
         self.test_batch_request()