ceph/src/seastar/tests/unit/lowres_clock_test.cc

   1 /*
   2  * This file is open source software, licensed to you under the terms
   3  * of the Apache License, Version 2.0 (the "License").  See the NOTICE file
   4  * distributed with this work for additional information regarding copyright
   5  * ownership.  You may not use this file except in compliance with the License.
   6  *
   7  * You may obtain a copy of the License at
   8  *
   9  *   http://www.apache.org/licenses/LICENSE-2.0
  10  *
  11  * Unless required by applicable law or agreed to in writing,
  12  * software distributed under the License is distributed on an
  13  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  14  * KIND, either express or implied.  See the License for the
  15  * specific language governing permissions and limitations
  16  * under the License.
  17  */
  18 /*
  19  * Copyright (C) 2017 ScyllaDB
  20  */
  21
  22 #include <seastar/testing/test_case.hh>
  23
  24 #include <seastar/core/do_with.hh>
  25 #include <seastar/core/lowres_clock.hh>
  26 #include <seastar/core/sleep.hh>
  27 #include <seastar/core/loop.hh>
  28
  29 #include <ctime>
  30
  31 #include <algorithm>
  32 #include <array>
  33 #include <chrono>
  34
  35 using namespace seastar;
  36
  37 //
  38 // Sanity check the accuracy of the steady low-resolution clock.
  39 //
  40 SEASTAR_TEST_CASE(steady_clock_sanity) {
  41     return do_with(lowres_clock::now(), [](auto &&t1) {
  42         static constexpr auto sleep_duration = std::chrono::milliseconds(100);
  43
  44         return ::seastar::sleep(sleep_duration).then([&t1] {
  45             auto const elapsed = lowres_clock::now() - t1;
  46             auto const minimum_elapsed = 0.9 * sleep_duration;
  47
  48             BOOST_REQUIRE(elapsed >= minimum_elapsed);
  49
  50             return make_ready_future<>();
  51         });
  52     });
  53 }
  54
  55 //
  56 // At the very least, we can verify that the low-resolution system clock is within a second of the
  57 // high-resolution system clock.
  58 //
  59 SEASTAR_TEST_CASE(system_clock_sanity) {
  60     static const auto check_matching = [] {
  61         auto const system_time = std::chrono::system_clock::now();
  62         auto const lowres_time = lowres_system_clock::now();
  63
  64         auto const t1 = std::chrono::system_clock::to_time_t(system_time);
  65         auto const t2 = lowres_system_clock::to_time_t(lowres_time);
  66
  67         std::tm *lt1 = std::localtime(&t1);
  68         std::tm *lt2 = std::localtime(&t2);
  69
  70         return (lt1->tm_isdst == lt2->tm_isdst) &&
  71                (lt1->tm_year == lt2->tm_year) &&
  72                (lt1->tm_mon == lt2->tm_mon) &&
  73                (lt1->tm_yday == lt2->tm_yday) &&
  74                (lt1->tm_mday == lt2->tm_mday) &&
  75                (lt1->tm_wday == lt2->tm_wday) &&
  76                (lt1->tm_hour == lt2->tm_hour) &&
  77                (lt1->tm_min == lt2->tm_min) &&
  78                (lt1->tm_sec == lt2->tm_sec);
  79     };
  80
  81     //
  82     // Check two out of three samples in order to account for the possibility that the high-resolution clock backing
  83     // the low-resoltuion clock was captured in the range of the 990th to 999th millisecond of the second. This would
  84     // make the low-resolution clock and the high-resolution clock disagree on the current second.
  85     //
  86
  87     return do_with(0ul, 0ul, [](std::size_t& index, std::size_t& success_count) {
  88         return repeat([&index, &success_count] {
  89             if (index >= 3) {
  90                 BOOST_REQUIRE_GE(success_count, 2u);
  91                 return make_ready_future<stop_iteration>(stop_iteration::yes);
  92             }
  93
  94             return ::seastar::sleep(std::chrono::milliseconds(10)).then([&index, &success_count] {
  95                 if (check_matching()) {
  96                     ++success_count;
  97                 }
  98
  99                 ++index;
 100                 return stop_iteration::no;
 101             });
 102         });
 103     });
 104 }
 105
 106 //
 107 // Verify that the low-resolution clock updates its reported time point over time.
 108 //
 109 SEASTAR_TEST_CASE(system_clock_dynamic) {
 110     return do_with(lowres_system_clock::now(), [](auto &&t1) {
 111         return seastar::sleep(std::chrono::milliseconds(100)).then([&t1] {
 112             auto const t2 = lowres_system_clock::now();
 113             BOOST_REQUIRE_NE(t1.time_since_epoch().count(), t2.time_since_epoch().count());
 114
 115             return make_ready_future<>();
 116         });
 117     });
 118 }