1 files changed, 117 insertions, 0 deletions
diff --git a/src/seastar/tests/unit/lowres_clock_test.cc b/src/seastar/tests/unit/lowres_clock_test.cc
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+++ b/src/seastar/tests/unit/lowres_clock_test.cc
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+/*
+ * This file is open source software, licensed to you under the terms
+ * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+ * distributed with this work for additional information regarding copyright
+ * ownership.  You may not use this file except in compliance with the License.
+ *
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+/*
+ * Copyright (C) 2017 ScyllaDB
+ */
+
+#include <seastar/testing/test_case.hh>
+
+#include <seastar/core/do_with.hh>
+#include <seastar/core/lowres_clock.hh>
+#include <seastar/core/sleep.hh>
+
+#include <ctime>
+
+#include <algorithm>
+#include <array>
+#include <chrono>
+
+using namespace seastar;
+
+//
+// Sanity check the accuracy of the steady low-resolution clock.
+//
+SEASTAR_TEST_CASE(steady_clock_sanity) {
+    return do_with(lowres_clock::now(), [](auto &&t1) {
+        static constexpr auto sleep_duration = std::chrono::milliseconds(100);
+
+        return ::seastar::sleep(sleep_duration).then([&t1] {
+            auto const elapsed = lowres_clock::now() - t1;
+            auto const minimum_elapsed = 0.9 * sleep_duration;
+
+            BOOST_REQUIRE(elapsed >= minimum_elapsed);
+
+            return make_ready_future<>();
+        });
+    });
+}
+
+//
+// At the very least, we can verify that the low-resolution system clock is within a second of the
+// high-resolution system clock.
+//
+SEASTAR_TEST_CASE(system_clock_sanity) {
+    static const auto check_matching = [] {
+        auto const system_time = std::chrono::system_clock::now();
+        auto const lowres_time = lowres_system_clock::now();
+
+        auto const t1 = std::chrono::system_clock::to_time_t(system_time);
+        auto const t2 = lowres_system_clock::to_time_t(lowres_time);
+
+        std::tm *lt1 = std::localtime(&t1);
+        std::tm *lt2 = std::localtime(&t2);
+
+        return (lt1->tm_isdst == lt2->tm_isdst) &&
+               (lt1->tm_year == lt2->tm_year) &&
+               (lt1->tm_mon == lt2->tm_mon) &&
+               (lt1->tm_yday == lt2->tm_yday) &&
+               (lt1->tm_mday == lt2->tm_mday) &&
+               (lt1->tm_wday == lt2->tm_wday) &&
+               (lt1->tm_hour == lt2->tm_hour) &&
+               (lt1->tm_min == lt2->tm_min) &&
+               (lt1->tm_sec == lt2->tm_sec);
+    };
+
+    //
+    // Check two out of three samples in order to account for the possibility that the high-resolution clock backing
+    // the low-resoltuion clock was captured in the range of the 990th to 999th millisecond of the second. This would
+    // make the low-resolution clock and the high-resolution clock disagree on the current second.
+    //
+
+    return do_with(0ul, 0ul, [](std::size_t& index, std::size_t& success_count) {
+        return repeat([&index, &success_count] {
+            if (index >= 3) {
+                BOOST_REQUIRE_GE(success_count, 2u);
+                return make_ready_future<stop_iteration>(stop_iteration::yes);
+            }
+
+            return ::seastar::sleep(std::chrono::milliseconds(10)).then([&index, &success_count] {
+                if (check_matching()) {
+                    ++success_count;
+                }
+
+                ++index;
+                return stop_iteration::no;
+            });
+        });
+    });
+}
+
+//
+// Verify that the low-resolution clock updates its reported time point over time.
+//
+SEASTAR_TEST_CASE(system_clock_dynamic) {
+    return do_with(lowres_system_clock::now(), [](auto &&t1) {
+        return seastar::sleep(std::chrono::milliseconds(100)).then([&t1] {
+            auto const t2 = lowres_system_clock::now();
+            BOOST_REQUIRE_NE(t1.time_since_epoch().count(), t2.time_since_epoch().count());
+
+            return make_ready_future<>();
+        });
+    });
+}