Add handler performance report

Builds/CMake/RippledCore.cmake

@@ -1079,6 +1079,7 @@ if (tests)
     src/test/rpc/ValidatorInfo_test.cpp
     src/test/rpc/ValidatorRPC_test.cpp
     src/test/rpc/Version_test.cpp
+    src/test/rpc/Handler_test.cpp
     #[===============================[
        test sources:
          subdir: server

src/test/rpc/Handler_test.cpp

@@ -0,0 +1,115 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of rippled: https://github.com/ripple/rippled
+    Copyright (c) 2023 Ripple Labs Inc.
+
+    Permission to use, copy, modify, and/or distribute this software for any
+    purpose  with  or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include <ripple/rpc/impl/Handler.h>
+#include "ripple/overlay/Peer.h"
+#include <limits>
+#include <test/jtx.h>
+
+#include <chrono>
+#include <iostream>
+#include <numeric>
+#include <random>
+
+namespace ripple::RPC {
+
+// NOTE This is a rather naiive effort at a microbenchmark. Ideally we want
+// Google Benchmark, or something similar. Also, this actually does not belong
+// to unit tests, as it makes little sense to run it in conditions very
+// dissimilar to how rippled will normally work.
+// TODO as https://github.com/XRPLF/rippled/issues/4765
+
+class Handler_test : public beast::unit_test::suite
+{
+    std::tuple<double, double, std::size_t>
+    time(std::size_t n, auto f, auto prng)
+    {
+        assert(n > 0);
+        // Prepare randomness cache away from performance measurements
+        std::vector<decltype(prng())> randomness;
+        randomness.reserve(n + 6);
+        for (std::size_t i = 0; i < n; i += 6)
+        {
+            randomness.push_back(prng());
+        }
+
+        double sum = 0;
+        double sum_squared = 0;
+        std::size_t j = 0;
+        while (j < n)
+        {
+            // Take 20 samples and throw away 7 from each end, using middle 6
+            std::array<long, 20> samples = {};
+            for (auto& s : samples)
+            {
+                auto start = std::chrono::high_resolution_clock::now();
+                f(randomness[j]);
+                s = (std::chrono::high_resolution_clock::now() - start).count();
+            }
+
+            std::sort(samples.begin(), samples.end());
+            for (std::size_t k = 7; k < 13; ++k)
+            {
+                j += 1;
+                sum += samples[k];
+                sum_squared += (samples[k] * samples[k]);
+            }
+        }
+
+        double const mean = sum / j;
+        return {mean, std::sqrt((sum_squared / j) - (mean * mean)), j};
+    }
+
+    void
+    reportLookupPerformance()
+    {
+        testcase("Handler lookup performance");
+
+        std::random_device dev;
+        std::ranlux48 prng(dev());
+
+        auto const names = getHandlerNames();
+        std::uniform_int_distribution<std::size_t> distr{0, names.size() - 1};
+
+        std::size_t dummy = 0;
+        auto const [mean, stdev, n] = time(
+            1'000'000,
+            [&](std::size_t i) {
+                auto const d = getHandler(1, false, names[i]);
+                dummy = dummy + i + (int)d->role_;
+            },
+            [&]() -> std::size_t { return distr(prng); });
+
+        std::cout << "mean=" << mean << " stdev=" << stdev << " N=" << n
+                  << '\n';
+
+        BEAST_EXPECT(dummy != 0);
+    }
+
+public:
+    void
+    run() override
+    {
+        reportLookupPerformance();
+    }
+};
+
+BEAST_DEFINE_TESTSUITE(Handler, rpc, ripple);
+
+}  // namespace ripple::RPC