Merge bitcoin#14982: rpc: Add getrpcinfo command

a0ac154 doc: Add getrpcinfo release notes (João Barbosa)
251a91c qa: Add tests for getrpcinfo (João Barbosa)
d0730f5 rpc: Add getrpcinfo command (João Barbosa)
068a8fc rpc: Track active commands (João Barbosa)
bf43832 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 bitcoin#14958 from where this was extracted).

Tree-SHA512: 7292cb6087f4c429973d991aa2b53ffa1327d5a213df7d6ba5fc69b01b2e1a411f6d1609fed9234896293317dab05f65064da48b8f2b4a998eba532591d31882

src/rpc/server.cpp

@@ -36,11 +36,39 @@ static std::map<std::string, std::unique_ptr<RPCTimerBase> > deadlineTimers;
 // Any commands submitted by this user will have their commands filtered based on the mapPlatformRestrictions
 static const std::string defaultPlatformUser = "platform-user";
 
+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)
@@ -321,7 +349,15 @@ static UniValue uptime(const JSONRPCRequest& jsonRequest)
                 "uptime\n"
                         "\nReturns the total uptime of the server.\n"
                         "\nResult:\n"
-                        "ttt        (numeric) The number of seconds that the server has been running\n"
+                "{\n"
+                " \"active_commands\" (array) All active commands\n"
+                "  [\n"
+                "   {               (object) Information about an active command\n"
+                "    \"method\"       (string)  The name of the RPC command \n"
+                "    \"duration\"     (numeric)  The running time in microseconds\n"
+                "   },...\n"
+                "  ]\n"
+                "}\n"
                         "\nExamples:\n"
                 + HelpExampleCli("uptime", "")
                 + HelpExampleRpc("uptime", "")
@@ -330,14 +366,41 @@ static UniValue uptime(const JSONRPCRequest& jsonRequest)
     return GetTime() - GetStartupTime();
 }
 
-/**
- * Call Table
- */
+static UniValue getrpcinfo(const JSONRPCRequest& request)
+{
+    if (request.fHelp || request.params.size() > 0)
+        throw std::runtime_error(
+                "getrpcinfo\n"
+                    "\nReturns details of the RPC server.\n"
+                    "\nResult:\n"
+                    "ttt        (numeric) The number of seconds that the server has been running\n"
+                    "\nExamples:\n"
+                + HelpExampleCli("getrpcinfo", "")
+                + HelpExampleRpc("getrpcinfo", "")
+        );
+
+    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",            "help",                   &help,                   {"command","subcommand"}  },
+    { "control",            "getrpcinfo",             &getrpcinfo,             {}  },
+    { "control",            "help",                   &help,                   {"command", "subcommand"}  },
     { "control",            "stop",                   &stop,                   {"wait"}  },
     { "control",            "uptime",                 &uptime,                 {}  },
 };
@@ -611,10 +674,9 @@ UniValue CRPCTable::execute(const JSONRPCRequest &request) const
         }
     }
 
-    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

@@ -0,0 +1,57 @@
+#!/usr/bin/env python3
+# Copyright (c) 2018 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Tests some generic aspects of the RPC interface."""
+
+from test_framework.test_framework import BitcoinTestFramework
+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...")
+
+        results = self.nodes[0].batch([
+            # A basic request that will work fine.
+            {"method": "getblockcount", "id": 1},
+            # Request that will fail.  The whole batch request should still
+            # work fine.
+            {"method": "invalidmethod", "id": 2},
+            # Another call that should succeed.
+            {"method": "getbestblockhash", "id": 3},
+        ])
+
+        result_by_id = {}
+        for res in results:
+            result_by_id[res["id"]] = res
+
+        assert_equal(result_by_id[1]['error'], None)
+        assert_equal(result_by_id[1]['result'], 0)
+
+        assert_equal(result_by_id[2]['error']['code'], -32601)
+        assert_equal(result_by_id[2]['result'], None)
+
+        assert_equal(result_by_id[3]['error'], None)
+        assert result_by_id[3]['result'] is not None
+
+    def run_test(self):
+        self.test_getrpcinfo()
+        self.test_batch_request()
+
+
+if __name__ == '__main__':
+    RPCInterfaceTest().main()

test/functional/test_runner.py

@@ -116,6 +116,7 @@
     'wallet_disableprivatekeys.py',
     'wallet_disableprivatekeys.py --usecli',
     'interface_http.py',
+    'interface_rpc.py',
     'rpc_psbt.py',
     'rpc_users.py',
     'feature_proxy.py',