aos/events/logging/logfile_utils_test.cc

#include "aos/events/logging/logfile_utils.h"

#include <chrono>
#include <string>

#include "aos/events/logging/logfile_sorting.h"
#include "aos/events/logging/test_message_generated.h"
#include "aos/flatbuffer_merge.h"
#include "aos/flatbuffers.h"
#include "aos/json_to_flatbuffer.h"
#include "aos/testing/tmpdir.h"
#include "gtest/gtest.h"

namespace aos {
namespace logger {
namespace testing {
namespace chrono = std::chrono;

// Creates a size prefixed flatbuffer from json.
template <typename T>
SizePrefixedFlatbufferDetachedBuffer<T> JsonToSizedFlatbuffer(
    const std::string_view data) {
  flatbuffers::FlatBufferBuilder fbb;
  fbb.ForceDefaults(true);
  fbb.FinishSizePrefixed(JsonToFlatbuffer<T>(data, &fbb));
  return fbb.Release();
}

// Tests that we can write and read 2 flatbuffers to file.
TEST(SpanReaderTest, ReadWrite) {
  const std::string logfile = aos::testing::TestTmpDir() + "/log.bfbs";
  unlink(logfile.c_str());

  const aos::SizePrefixedFlatbufferDetachedBuffer<TestMessage> m1 =
      JsonToSizedFlatbuffer<TestMessage>(R"({ "value": 1 })");
  const aos::SizePrefixedFlatbufferDetachedBuffer<TestMessage> m2 =
      JsonToSizedFlatbuffer<TestMessage>(R"({ "value": 2 })");

  {
    DetachedBufferWriter writer(logfile, std::make_unique<DummyEncoder>());
    writer.QueueSpan(m1.span());
    writer.QueueSpan(m2.span());
  }

  SpanReader reader(logfile);

  EXPECT_EQ(reader.filename(), logfile);
  EXPECT_EQ(reader.ReadMessage(), m1.span());
  EXPECT_EQ(reader.ReadMessage(), m2.span());
  EXPECT_EQ(reader.ReadMessage(), absl::Span<const uint8_t>());
}

// Tests that we can actually parse the resulting messages at a basic level
// through MessageReader.
TEST(MessageReaderTest, ReadWrite) {
  const std::string logfile = aos::testing::TestTmpDir() + "/log.bfbs";
  unlink(logfile.c_str());

  const aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> config =
      JsonToSizedFlatbuffer<LogFileHeader>(
          R"({ "max_out_of_order_duration": 100000000 })");
  const aos::SizePrefixedFlatbufferDetachedBuffer<MessageHeader> m1 =
      JsonToSizedFlatbuffer<MessageHeader>(
          R"({ "channel_index": 0, "monotonic_sent_time": 1 })");
  const aos::SizePrefixedFlatbufferDetachedBuffer<MessageHeader> m2 =
      JsonToSizedFlatbuffer<MessageHeader>(
          R"({ "channel_index": 0, "monotonic_sent_time": 2 })");

  {
    DetachedBufferWriter writer(logfile, std::make_unique<DummyEncoder>());
    writer.QueueSpan(config.span());
    writer.QueueSpan(m1.span());
    writer.QueueSpan(m2.span());
  }

  MessageReader reader(logfile);

  EXPECT_EQ(reader.filename(), logfile);

  EXPECT_EQ(
      reader.max_out_of_order_duration(),
      std::chrono::nanoseconds(config.message().max_out_of_order_duration()));
  EXPECT_EQ(reader.newest_timestamp(), monotonic_clock::min_time);
  EXPECT_TRUE(reader.ReadMessage());
  EXPECT_EQ(reader.newest_timestamp(),
            monotonic_clock::time_point(chrono::nanoseconds(1)));
  EXPECT_TRUE(reader.ReadMessage());
  EXPECT_EQ(reader.newest_timestamp(),
            monotonic_clock::time_point(chrono::nanoseconds(2)));
  EXPECT_FALSE(reader.ReadMessage());
}

// Tests that we explode when messages are too far out of order.
TEST(PartsMessageReaderDeathTest, TooFarOutOfOrder) {
  const std::string logfile0 = aos::testing::TestTmpDir() + "/log0.bfbs";
  unlink(logfile0.c_str());

  const aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> config0 =
      JsonToSizedFlatbuffer<LogFileHeader>(
          R"({
  "max_out_of_order_duration": 100000000,
  "configuration": {},
  "log_event_uuid": "30ef1283-81d7-4004-8c36-1c162dbcb2b2",
  "parts_uuid": "2a05d725-5d5c-4c0b-af42-88de2f3c3876",
  "parts_index": 0
})");

  const aos::SizePrefixedFlatbufferDetachedBuffer<MessageHeader> m1 =
      JsonToSizedFlatbuffer<MessageHeader>(
          R"({ "channel_index": 0, "monotonic_sent_time": 100000000 })");
  const aos::SizePrefixedFlatbufferDetachedBuffer<MessageHeader> m2 =
      JsonToSizedFlatbuffer<MessageHeader>(
          R"({ "channel_index": 0, "monotonic_sent_time": 0 })");
  const aos::SizePrefixedFlatbufferDetachedBuffer<MessageHeader> m3 =
      JsonToSizedFlatbuffer<MessageHeader>(
          R"({ "channel_index": 0, "monotonic_sent_time": -1 })");

  {
    DetachedBufferWriter writer(logfile0, std::make_unique<DummyEncoder>());
    writer.QueueSpan(config0.span());
    writer.QueueSpan(m1.span());
    writer.QueueSpan(m2.span());
    writer.QueueSpan(m3.span());
  }

  const std::vector<LogFile> parts = SortParts({logfile0});

  PartsMessageReader reader(parts[0].parts[0]);

  EXPECT_TRUE(reader.ReadMessage());
  EXPECT_TRUE(reader.ReadMessage());
  EXPECT_DEATH({ reader.ReadMessage(); }, "-0.000000001sec vs. 0.000000000sec");
}

// Tests that we can transparently re-assemble part files with a
// PartsMessageReader.
TEST(PartsMessageReaderTest, ReadWrite) {
  const std::string logfile0 = aos::testing::TestTmpDir() + "/log0.bfbs";
  const std::string logfile1 = aos::testing::TestTmpDir() + "/log1.bfbs";
  unlink(logfile0.c_str());
  unlink(logfile1.c_str());

  const aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> config0 =
      JsonToSizedFlatbuffer<LogFileHeader>(
          R"({
  "max_out_of_order_duration": 100000000,
  "configuration": {},
  "log_event_uuid": "30ef1283-81d7-4004-8c36-1c162dbcb2b2",
  "parts_uuid": "2a05d725-5d5c-4c0b-af42-88de2f3c3876",
  "parts_index": 0
})");
  const aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> config1 =
      JsonToSizedFlatbuffer<LogFileHeader>(
          R"({
  "max_out_of_order_duration": 200000000,
  "monotonic_start_time": 0,
  "realtime_start_time": 0,
  "configuration": {},
  "log_event_uuid": "30ef1283-81d7-4004-8c36-1c162dbcb2b2",
  "parts_uuid": "2a05d725-5d5c-4c0b-af42-88de2f3c3876",
  "parts_index": 1
})");

  const aos::SizePrefixedFlatbufferDetachedBuffer<MessageHeader> m1 =
      JsonToSizedFlatbuffer<MessageHeader>(
          R"({ "channel_index": 0, "monotonic_sent_time": 1 })");
  const aos::SizePrefixedFlatbufferDetachedBuffer<MessageHeader> m2 =
      JsonToSizedFlatbuffer<MessageHeader>(
          R"({ "channel_index": 0, "monotonic_sent_time": 2 })");

  {
    DetachedBufferWriter writer(logfile0, std::make_unique<DummyEncoder>());
    writer.QueueSpan(config0.span());
    writer.QueueSpan(m1.span());
  }
  {
    DetachedBufferWriter writer(logfile1, std::make_unique<DummyEncoder>());
    writer.QueueSpan(config1.span());
    writer.QueueSpan(m2.span());
  }

  const std::vector<LogFile> parts = SortParts({logfile0, logfile1});

  PartsMessageReader reader(parts[0].parts[0]);

  EXPECT_EQ(reader.filename(), logfile0);

  // Confirm that the timestamps track, and the filename also updates.
  // Read the first message.
  EXPECT_EQ(reader.newest_timestamp(), monotonic_clock::min_time);
  EXPECT_EQ(
      reader.max_out_of_order_duration(),
      std::chrono::nanoseconds(config0.message().max_out_of_order_duration()));
  EXPECT_TRUE(reader.ReadMessage());
  EXPECT_EQ(reader.filename(), logfile0);
  EXPECT_EQ(reader.newest_timestamp(),
            monotonic_clock::time_point(chrono::nanoseconds(1)));
  EXPECT_EQ(
      reader.max_out_of_order_duration(),
      std::chrono::nanoseconds(config0.message().max_out_of_order_duration()));

  // Read the second message.
  EXPECT_TRUE(reader.ReadMessage());
  EXPECT_EQ(reader.filename(), logfile1);
  EXPECT_EQ(reader.newest_timestamp(),
            monotonic_clock::time_point(chrono::nanoseconds(2)));
  EXPECT_EQ(
      reader.max_out_of_order_duration(),
      std::chrono::nanoseconds(config1.message().max_out_of_order_duration()));

  // And then confirm that reading again returns no message.
  EXPECT_FALSE(reader.ReadMessage());
  EXPECT_EQ(reader.filename(), logfile1);
  EXPECT_EQ(
      reader.max_out_of_order_duration(),
      std::chrono::nanoseconds(config1.message().max_out_of_order_duration()));
  EXPECT_EQ(reader.newest_timestamp(), monotonic_clock::max_time);
}

// Tests that Message's operator < works as expected.
TEST(MessageTest, Sorting) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();

  Message m1{.channel_index = 0,
             .queue_index = 0,
             .timestamp = e + chrono::milliseconds(1),
             .data = SizePrefixedFlatbufferVector<MessageHeader>::Empty()};
  Message m2{.channel_index = 0,
             .queue_index = 0,
             .timestamp = e + chrono::milliseconds(2),
             .data = SizePrefixedFlatbufferVector<MessageHeader>::Empty()};

  EXPECT_LT(m1, m2);
  EXPECT_GE(m2, m1);

  m1.timestamp = e;
  m2.timestamp = e;

  m1.channel_index = 1;
  m2.channel_index = 2;

  EXPECT_LT(m1, m2);
  EXPECT_GE(m2, m1);

  m1.channel_index = 0;
  m2.channel_index = 0;
  m1.queue_index = 0;
  m2.queue_index = 1;

  EXPECT_LT(m1, m2);
  EXPECT_GE(m2, m1);
}

aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> MakeHeader(
    const aos::FlatbufferDetachedBuffer<Configuration> &config,
    const std::string_view json) {
  flatbuffers::FlatBufferBuilder fbb;
  fbb.ForceDefaults(true);
  flatbuffers::Offset<Configuration> config_offset =
      aos::CopyFlatBuffer(config, &fbb);
  LogFileHeader::Builder header_builder(fbb);
  header_builder.add_configuration(config_offset);
  fbb.Finish(header_builder.Finish());
  aos::FlatbufferDetachedBuffer<LogFileHeader> config_header(fbb.Release());

  aos::FlatbufferDetachedBuffer<LogFileHeader> header_updates(
      JsonToFlatbuffer<LogFileHeader>(json));
  CHECK(header_updates.Verify());
  flatbuffers::FlatBufferBuilder fbb2;
  fbb2.ForceDefaults(true);
  fbb2.FinishSizePrefixed(
      aos::MergeFlatBuffers(config_header, header_updates, &fbb2));
  return fbb2.Release();
}

class SortingElementTest : public ::testing::Test {
 public:
  SortingElementTest()
      : config_(JsonToFlatbuffer<Configuration>(
            R"({
  "channels": [
    {
      "name": "/a",
      "type": "aos.logger.testing.TestMessage",
      "source_node": "pi1",
      "destination_nodes": [
        {
          "name": "pi2"
        },
        {
          "name": "pi3"
        }
      ]
    },
    {
      "name": "/b",
      "type": "aos.logger.testing.TestMessage",
      "source_node": "pi1"
    },
    {
      "name": "/c",
      "type": "aos.logger.testing.TestMessage",
      "source_node": "pi1"
    }
  ],
  "nodes": [
    {
      "name": "pi1"
    },
    {
      "name": "pi2"
    },
    {
      "name": "pi3"
    }
  ]
}
)")),
        config0_(MakeHeader(config_, R"({
  /* 100ms */
  "max_out_of_order_duration": 100000000,
  "node": {
    "name": "pi1"
  },
  "logger_node": {
    "name": "pi1"
  },
  "monotonic_start_time": 1000000,
  "realtime_start_time": 1000000000000,
  "log_event_uuid": "30ef1283-81d7-4004-8c36-1c162dbcb2b2",
  "parts_uuid": "2a05d725-5d5c-4c0b-af42-88de2f3c3876",
  "parts_index": 0
})")),
        config1_(MakeHeader(config_,
                            R"({
  /* 100ms */
  "max_out_of_order_duration": 100000000,
  "node": {
    "name": "pi1"
  },
  "logger_node": {
    "name": "pi1"
  },
  "monotonic_start_time": 1000000,
  "realtime_start_time": 1000000000000,
  "log_event_uuid": "30ef1283-81d7-4004-8c36-1c162dbcb2b2",
  "parts_uuid": "bafe9f8e-7dea-4bd9-95f5-3d8390e49208",
  "parts_index": 0
})")),
        config2_(MakeHeader(config_,
                            R"({
  /* 100ms */
  "max_out_of_order_duration": 100000000,
  "node": {
    "name": "pi2"
  },
  "logger_node": {
    "name": "pi2"
  },
  "monotonic_start_time": 0,
  "realtime_start_time": 1000000000000,
  "log_event_uuid": "cb89a1ce-c4b6-4747-a647-051f09ac888c",
  "parts_uuid": "e6bff6c6-757f-4675-90d8-3bfb642870e6",
  "parts_index": 0
})")),
        config3_(MakeHeader(config_,
                            R"({
  /* 100ms */
  "max_out_of_order_duration": 100000000,
  "node": {
    "name": "pi1"
  },
  "logger_node": {
    "name": "pi1"
  },
  "monotonic_start_time": 2000000,
  "realtime_start_time": 1000000000,
  "log_event_uuid": "cb26b86a-473e-4f74-8403-50eb92ed60ad",
  "parts_uuid": "1f098701-949f-4392-81f9-be463e2d7bd4",
  "parts_index": 0
})")),
        config4_(MakeHeader(config_,
                            R"({
  /* 100ms */
  "max_out_of_order_duration": 100000000,
  "node": {
    "name": "pi2"
  },
  "logger_node": {
    "name": "pi1"
  },
  "monotonic_start_time": 2000000,
  "realtime_start_time": 1000000000,
  "log_event_uuid": "30ef1283-81d7-4004-8c36-1c162dbcb2b2",
  "parts_uuid": "4e560a47-e2a6-4ce3-a925-490bebc947c5",
  "parts_index": 0
})")) {
    unlink(logfile0_.c_str());
    unlink(logfile1_.c_str());
    unlink(logfile2_.c_str());
    queue_index_.resize(kChannels);
  }

 protected:
  static constexpr size_t kChannels = 3u;

  flatbuffers::DetachedBuffer MakeLogMessage(
      const aos::monotonic_clock::time_point monotonic_now, int channel_index,
      int value) {
    flatbuffers::FlatBufferBuilder message_fbb;
    message_fbb.ForceDefaults(true);
    TestMessage::Builder test_message_builder(message_fbb);
    test_message_builder.add_value(value);
    message_fbb.Finish(test_message_builder.Finish());

    aos::Context context;
    context.monotonic_event_time = monotonic_now;
    context.realtime_event_time = aos::realtime_clock::epoch() +
                                  chrono::seconds(1000) +
                                  monotonic_now.time_since_epoch();
    context.queue_index = queue_index_[channel_index];
    context.size = message_fbb.GetSize();
    context.data = message_fbb.GetBufferPointer();

    ++queue_index_[channel_index];

    flatbuffers::FlatBufferBuilder fbb;
    fbb.FinishSizePrefixed(
        PackMessage(&fbb, context, channel_index, LogType::kLogMessage));

    return fbb.Release();
  }

  flatbuffers::DetachedBuffer MakeTimestampMessage(
      const aos::monotonic_clock::time_point sender_monotonic_now,
      int channel_index, chrono::nanoseconds receiver_monotonic_offset,
      monotonic_clock::time_point monotonic_timestamp_time =
          monotonic_clock::min_time) {
    const monotonic_clock::time_point monotonic_sent_time =
        sender_monotonic_now + receiver_monotonic_offset;

    flatbuffers::FlatBufferBuilder fbb;
    fbb.ForceDefaults(true);

    logger::MessageHeader::Builder message_header_builder(fbb);

    message_header_builder.add_channel_index(channel_index);

    message_header_builder.add_queue_index(queue_index_[channel_index] - 1 +
                                           100);
    message_header_builder.add_monotonic_sent_time(
        monotonic_sent_time.time_since_epoch().count());
    message_header_builder.add_realtime_sent_time(
        (aos::realtime_clock::epoch() + chrono::seconds(1000) +
         monotonic_sent_time.time_since_epoch())
            .time_since_epoch()
            .count());

    message_header_builder.add_monotonic_remote_time(
        sender_monotonic_now.time_since_epoch().count());
    message_header_builder.add_realtime_remote_time(
        (aos::realtime_clock::epoch() + chrono::seconds(1000) +
         sender_monotonic_now.time_since_epoch())
            .time_since_epoch()
            .count());
    message_header_builder.add_remote_queue_index(queue_index_[channel_index] -
                                                  1);

    if (monotonic_timestamp_time != monotonic_clock::min_time) {
      message_header_builder.add_monotonic_timestamp_time(
          monotonic_timestamp_time.time_since_epoch().count());
    }

    fbb.FinishSizePrefixed(message_header_builder.Finish());
    LOG(INFO) << aos::FlatbufferToJson(
        aos::SizePrefixedFlatbufferSpan<MessageHeader>(
            absl::Span<uint8_t>(fbb.GetBufferPointer(), fbb.GetSize())));

    return fbb.Release();
  }

  const std::string logfile0_ = aos::testing::TestTmpDir() + "/log0.bfbs";
  const std::string logfile1_ = aos::testing::TestTmpDir() + "/log1.bfbs";
  const std::string logfile2_ = aos::testing::TestTmpDir() + "/log2.bfbs";

  const aos::FlatbufferDetachedBuffer<Configuration> config_;
  const aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> config0_;
  const aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> config1_;
  const aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> config2_;
  const aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> config3_;
  const aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> config4_;

  std::vector<uint32_t> queue_index_;
};

using LogPartsSorterTest = SortingElementTest;
using LogPartsSorterDeathTest = LogPartsSorterTest;
using NodeMergerTest = SortingElementTest;
using TimestampMapperTest = SortingElementTest;

// Tests that we can pull messages out of a log sorted in order.
TEST_F(LogPartsSorterTest, Pull) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer(logfile0_, std::make_unique<DummyEncoder>());
    writer.QueueSpan(config0_.span());
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005));
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 1, 0x105));
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x006));
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1901), 1, 0x107));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_});

  LogPartsSorter parts_sorter(parts[0].parts[0]);

  // Confirm we aren't sorted until any time until the message is popped.
  // Peeking shouldn't change the sorted until time.
  EXPECT_EQ(parts_sorter.sorted_until(), monotonic_clock::min_time);

  std::deque<Message> output;

  ASSERT_TRUE(parts_sorter.Front() != nullptr);
  output.emplace_back(std::move(*parts_sorter.Front()));
  parts_sorter.PopFront();
  EXPECT_EQ(parts_sorter.sorted_until(), e + chrono::milliseconds(1900));

  ASSERT_TRUE(parts_sorter.Front() != nullptr);
  output.emplace_back(std::move(*parts_sorter.Front()));
  parts_sorter.PopFront();
  EXPECT_EQ(parts_sorter.sorted_until(), e + chrono::milliseconds(1900));

  ASSERT_TRUE(parts_sorter.Front() != nullptr);
  output.emplace_back(std::move(*parts_sorter.Front()));
  parts_sorter.PopFront();
  EXPECT_EQ(parts_sorter.sorted_until(), monotonic_clock::max_time);

  ASSERT_TRUE(parts_sorter.Front() != nullptr);
  output.emplace_back(std::move(*parts_sorter.Front()));
  parts_sorter.PopFront();
  EXPECT_EQ(parts_sorter.sorted_until(), monotonic_clock::max_time);

  ASSERT_TRUE(parts_sorter.Front() == nullptr);

  EXPECT_EQ(output[0].timestamp, e + chrono::milliseconds(1000));
  EXPECT_EQ(output[1].timestamp, e + chrono::milliseconds(1000));
  EXPECT_EQ(output[2].timestamp, e + chrono::milliseconds(1901));
  EXPECT_EQ(output[3].timestamp, e + chrono::milliseconds(2000));
}

// Tests that we can pull messages out of a log sorted in order.
TEST_F(LogPartsSorterTest, WayBeforeStart) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer(logfile0_, std::make_unique<DummyEncoder>());
    writer.QueueSpan(config0_.span());
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e - chrono::milliseconds(500), 0, 0x005));
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e - chrono::milliseconds(10), 2, 0x005));
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e - chrono::milliseconds(1000), 1, 0x105));
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x006));
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1901), 1, 0x107));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_});

  LogPartsSorter parts_sorter(parts[0].parts[0]);

  // Confirm we aren't sorted until any time until the message is popped.
  // Peeking shouldn't change the sorted until time.
  EXPECT_EQ(parts_sorter.sorted_until(), monotonic_clock::min_time);

  std::deque<Message> output;

  for (monotonic_clock::time_point t :
       {e + chrono::milliseconds(1900), e + chrono::milliseconds(1900),
        e + chrono::milliseconds(1900), monotonic_clock::max_time,
        monotonic_clock::max_time}) {
    ASSERT_TRUE(parts_sorter.Front() != nullptr);
    output.emplace_back(std::move(*parts_sorter.Front()));
    parts_sorter.PopFront();
    EXPECT_EQ(parts_sorter.sorted_until(), t);
  }

  ASSERT_TRUE(parts_sorter.Front() == nullptr);

  EXPECT_EQ(output[0].timestamp, e - chrono::milliseconds(1000));
  EXPECT_EQ(output[1].timestamp, e - chrono::milliseconds(500));
  EXPECT_EQ(output[2].timestamp, e - chrono::milliseconds(10));
  EXPECT_EQ(output[3].timestamp, e + chrono::milliseconds(1901));
  EXPECT_EQ(output[4].timestamp, e + chrono::milliseconds(2000));
}

// Tests that messages too far out of order trigger death.
TEST_F(LogPartsSorterDeathTest, Pull) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer(logfile0_, std::make_unique<DummyEncoder>());
    writer.QueueSpan(config0_.span());
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005));
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 1, 0x105));
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2001), 0, 0x006));
    // The following message is too far out of order and will trigger the CHECK.
    writer.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1900), 1, 0x107));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_});

  LogPartsSorter parts_sorter(parts[0].parts[0]);

  // Confirm we aren't sorted until any time until the message is popped.
  // Peeking shouldn't change the sorted until time.
  EXPECT_EQ(parts_sorter.sorted_until(), monotonic_clock::min_time);
  std::deque<Message> output;

  ASSERT_TRUE(parts_sorter.Front() != nullptr);
  parts_sorter.PopFront();
  ASSERT_TRUE(parts_sorter.Front() != nullptr);
  ASSERT_TRUE(parts_sorter.Front() != nullptr);
  parts_sorter.PopFront();

  EXPECT_DEATH({ parts_sorter.Front(); }, "Max out of order of 100000000ns exceeded.");
}

// Tests that we can merge data from 2 separate files, including duplicate data.
TEST_F(NodeMergerTest, TwoFileMerger) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config1_.span());

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005));
    writer1.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1001), 1, 0x105));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x006));
    writer1.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1002), 1, 0x106));

    // Make a duplicate!
    SizePrefixedFlatbufferDetachedBuffer<MessageHeader> msg(
        MakeLogMessage(e + chrono::milliseconds(3000), 0, 0x007));
    writer0.QueueSpan(msg.span());
    writer1.QueueSpan(msg.span());

    writer1.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(3002), 1, 0x107));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});
  ASSERT_EQ(parts.size(), 1u);

  NodeMerger merger(FilterPartsForNode(parts, "pi1"));

  EXPECT_EQ(merger.sorted_until(), monotonic_clock::min_time);

  std::deque<Message> output;

  EXPECT_EQ(merger.sorted_until(), monotonic_clock::min_time);
  ASSERT_TRUE(merger.Front() != nullptr);
  EXPECT_EQ(merger.sorted_until(), e + chrono::milliseconds(1900));

  output.emplace_back(std::move(*merger.Front()));
  merger.PopFront();
  EXPECT_EQ(merger.sorted_until(), e + chrono::milliseconds(1900));

  ASSERT_TRUE(merger.Front() != nullptr);
  output.emplace_back(std::move(*merger.Front()));
  merger.PopFront();
  EXPECT_EQ(merger.sorted_until(), e + chrono::milliseconds(2900));

  ASSERT_TRUE(merger.Front() != nullptr);
  output.emplace_back(std::move(*merger.Front()));
  merger.PopFront();
  EXPECT_EQ(merger.sorted_until(), e + chrono::milliseconds(2900));

  ASSERT_TRUE(merger.Front() != nullptr);
  output.emplace_back(std::move(*merger.Front()));
  merger.PopFront();
  EXPECT_EQ(merger.sorted_until(), e + chrono::milliseconds(2900));

  ASSERT_TRUE(merger.Front() != nullptr);
  output.emplace_back(std::move(*merger.Front()));
  merger.PopFront();
  EXPECT_EQ(merger.sorted_until(), monotonic_clock::max_time);

  ASSERT_TRUE(merger.Front() != nullptr);
  output.emplace_back(std::move(*merger.Front()));
  merger.PopFront();
  EXPECT_EQ(merger.sorted_until(), monotonic_clock::max_time);

  ASSERT_TRUE(merger.Front() == nullptr);

  EXPECT_EQ(output[0].timestamp, e + chrono::milliseconds(1000));
  EXPECT_EQ(output[1].timestamp, e + chrono::milliseconds(1001));
  EXPECT_EQ(output[2].timestamp, e + chrono::milliseconds(1002));
  EXPECT_EQ(output[3].timestamp, e + chrono::milliseconds(2000));
  EXPECT_EQ(output[4].timestamp, e + chrono::milliseconds(3000));
  EXPECT_EQ(output[5].timestamp, e + chrono::milliseconds(3002));
}

// Tests that we can merge timestamps with various combinations of
// monotonic_timestamp_time.
TEST_F(NodeMergerTest, TwoFileTimestampMerger) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config1_.span());

    // Neither has it.
    MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005);
    writer0.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100)));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100)));

    // First only has it.
    MakeLogMessage(e + chrono::milliseconds(1001), 0, 0x006);
    writer0.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1001), 0, chrono::seconds(100),
        e + chrono::nanoseconds(971)));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1001), 0, chrono::seconds(100)));

    // Second only has it.
    MakeLogMessage(e + chrono::milliseconds(1002), 0, 0x007);
    writer0.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1002), 0, chrono::seconds(100)));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1002), 0, chrono::seconds(100),
        e + chrono::nanoseconds(972)));

    // Both have it.
    MakeLogMessage(e + chrono::milliseconds(1003), 0, 0x008);
    writer0.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1003), 0, chrono::seconds(100),
        e + chrono::nanoseconds(973)));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1003), 0, chrono::seconds(100),
        e + chrono::nanoseconds(973)));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});
  ASSERT_EQ(parts.size(), 1u);

  NodeMerger merger(FilterPartsForNode(parts, "pi1"));

  EXPECT_EQ(merger.sorted_until(), monotonic_clock::min_time);

  std::deque<Message> output;

  for (int i = 0; i < 4; ++i) {
    ASSERT_TRUE(merger.Front() != nullptr);
    output.emplace_back(std::move(*merger.Front()));
    merger.PopFront();
  }
  ASSERT_TRUE(merger.Front() == nullptr);

  EXPECT_EQ(output[0].timestamp, e + chrono::milliseconds(101000));
  EXPECT_FALSE(output[0].data.message().has_monotonic_timestamp_time());
  EXPECT_EQ(output[1].timestamp, e + chrono::milliseconds(101001));
  EXPECT_TRUE(output[1].data.message().has_monotonic_timestamp_time());
  EXPECT_EQ(output[1].data.message().monotonic_timestamp_time(), 971);
  EXPECT_EQ(output[2].timestamp, e + chrono::milliseconds(101002));
  EXPECT_TRUE(output[2].data.message().has_monotonic_timestamp_time());
  EXPECT_EQ(output[2].data.message().monotonic_timestamp_time(), 972);
  EXPECT_EQ(output[3].timestamp, e + chrono::milliseconds(101003));
  EXPECT_TRUE(output[3].data.message().has_monotonic_timestamp_time());
  EXPECT_EQ(output[3].data.message().monotonic_timestamp_time(), 973);
}

// Tests that we can match timestamps on delivered messages.
TEST_F(TimestampMapperTest, ReadNode0First) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config2_.span());

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x006));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(2000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(3000), 0, 0x007));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(3000), 0, chrono::seconds(100)));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});

  ASSERT_EQ(parts[0].logger_node, "pi1");
  ASSERT_EQ(parts[1].logger_node, "pi2");

  size_t mapper0_count = 0;
  TimestampMapper mapper0(FilterPartsForNode(parts, "pi1"));
  mapper0.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper0_count; });
  size_t mapper1_count = 0;
  TimestampMapper mapper1(FilterPartsForNode(parts, "pi2"));
  mapper1.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper1_count; });

  mapper0.AddPeer(&mapper1);
  mapper1.AddPeer(&mapper0);

  {
    std::deque<TimestampedMessage> output0;

    EXPECT_EQ(mapper0_count, 0u);
    EXPECT_EQ(mapper1_count, 0u);
    ASSERT_TRUE(mapper0.Front() != nullptr);
    EXPECT_EQ(mapper0_count, 1u);
    EXPECT_EQ(mapper1_count, 0u);
    output0.emplace_back(std::move(*mapper0.Front()));
    mapper0.PopFront();
    EXPECT_EQ(mapper0.sorted_until(), e + chrono::milliseconds(1900));
    EXPECT_EQ(mapper0_count, 1u);
    EXPECT_EQ(mapper1_count, 0u);

    ASSERT_TRUE(mapper0.Front() != nullptr);
    EXPECT_EQ(mapper0_count, 2u);
    EXPECT_EQ(mapper1_count, 0u);
    output0.emplace_back(std::move(*mapper0.Front()));
    mapper0.PopFront();
    EXPECT_EQ(mapper0.sorted_until(), e + chrono::milliseconds(2900));

    ASSERT_TRUE(mapper0.Front() != nullptr);
    output0.emplace_back(std::move(*mapper0.Front()));
    mapper0.PopFront();
    EXPECT_EQ(mapper0.sorted_until(), monotonic_clock::max_time);

    EXPECT_EQ(mapper0_count, 3u);
    EXPECT_EQ(mapper1_count, 0u);

    ASSERT_TRUE(mapper0.Front() == nullptr);

    EXPECT_EQ(output0[0].monotonic_event_time, e + chrono::milliseconds(1000));
    EXPECT_TRUE(output0[0].data.Verify());
    EXPECT_EQ(output0[1].monotonic_event_time, e + chrono::milliseconds(2000));
    EXPECT_TRUE(output0[1].data.Verify());
    EXPECT_EQ(output0[2].monotonic_event_time, e + chrono::milliseconds(3000));
    EXPECT_TRUE(output0[2].data.Verify());
  }

  {
    SCOPED_TRACE("Trying node1 now");
    std::deque<TimestampedMessage> output1;

    EXPECT_EQ(mapper0_count, 3u);
    EXPECT_EQ(mapper1_count, 0u);

    ASSERT_TRUE(mapper1.Front() != nullptr);
    EXPECT_EQ(mapper0_count, 3u);
    EXPECT_EQ(mapper1_count, 1u);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(),
              e + chrono::seconds(100) + chrono::milliseconds(1900));
    EXPECT_EQ(mapper0_count, 3u);
    EXPECT_EQ(mapper1_count, 1u);

    ASSERT_TRUE(mapper1.Front() != nullptr);
    EXPECT_EQ(mapper0_count, 3u);
    EXPECT_EQ(mapper1_count, 2u);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(),
              e + chrono::seconds(100) + chrono::milliseconds(2900));

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(), monotonic_clock::max_time);

    EXPECT_EQ(mapper0_count, 3u);
    EXPECT_EQ(mapper1_count, 3u);

    ASSERT_TRUE(mapper1.Front() == nullptr);

    EXPECT_EQ(mapper0_count, 3u);
    EXPECT_EQ(mapper1_count, 3u);

    EXPECT_EQ(output1[0].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(1000));
    EXPECT_TRUE(output1[0].data.Verify());
    EXPECT_EQ(output1[1].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(2000));
    EXPECT_TRUE(output1[1].data.Verify());
    EXPECT_EQ(output1[2].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(3000));
    EXPECT_TRUE(output1[2].data.Verify());
  }
}

// Tests that a MessageHeader with monotonic_timestamp_time set gets properly
// returned.
TEST_F(TimestampMapperTest, MessageWithTimestampTime) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config4_.span());

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100),
        e + chrono::nanoseconds(971)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x006));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(2000), 0, chrono::seconds(100),
        e + chrono::nanoseconds(5458)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(3000), 0, 0x007));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(3000), 0, chrono::seconds(100)));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});

  for (const auto &p : parts) {
    LOG(INFO) << p;
  }

  ASSERT_EQ(parts.size(), 1u);

  size_t mapper0_count = 0;
  TimestampMapper mapper0(FilterPartsForNode(parts, "pi1"));
  mapper0.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper0_count; });
  size_t mapper1_count = 0;
  TimestampMapper mapper1(FilterPartsForNode(parts, "pi2"));
  mapper1.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper1_count; });

  mapper0.AddPeer(&mapper1);
  mapper1.AddPeer(&mapper0);

  {
    std::deque<TimestampedMessage> output0;

    for (int i = 0; i < 3; ++i) {
      ASSERT_TRUE(mapper0.Front() != nullptr) << ": " << i;
      output0.emplace_back(std::move(*mapper0.Front()));
      mapper0.PopFront();
    }

    ASSERT_TRUE(mapper0.Front() == nullptr);

    EXPECT_EQ(output0[0].monotonic_event_time, e + chrono::milliseconds(1000));
    EXPECT_EQ(output0[0].monotonic_timestamp_time, monotonic_clock::min_time);
    EXPECT_TRUE(output0[0].data.Verify());
    EXPECT_EQ(output0[1].monotonic_event_time, e + chrono::milliseconds(2000));
    EXPECT_EQ(output0[1].monotonic_timestamp_time, monotonic_clock::min_time);
    EXPECT_TRUE(output0[1].data.Verify());
    EXPECT_EQ(output0[2].monotonic_event_time, e + chrono::milliseconds(3000));
    EXPECT_EQ(output0[2].monotonic_timestamp_time, monotonic_clock::min_time);
    EXPECT_TRUE(output0[2].data.Verify());
  }

  {
    SCOPED_TRACE("Trying node1 now");
    std::deque<TimestampedMessage> output1;

    for (int i = 0; i < 3; ++i) {
      ASSERT_TRUE(mapper1.Front() != nullptr);
      output1.emplace_back(std::move(*mapper1.Front()));
      mapper1.PopFront();
    }

    ASSERT_TRUE(mapper1.Front() == nullptr);

    EXPECT_EQ(output1[0].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(1000));
    EXPECT_EQ(output1[0].monotonic_timestamp_time,
              e + chrono::nanoseconds(971));
    EXPECT_TRUE(output1[0].data.Verify());
    EXPECT_EQ(output1[1].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(2000));
    EXPECT_EQ(output1[1].monotonic_timestamp_time,
              e + chrono::nanoseconds(5458));
    EXPECT_TRUE(output1[1].data.Verify());
    EXPECT_EQ(output1[2].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(3000));
    EXPECT_EQ(output1[2].monotonic_timestamp_time, monotonic_clock::min_time);
    EXPECT_TRUE(output1[2].data.Verify());
  }

  EXPECT_EQ(mapper0_count, 3u);
  EXPECT_EQ(mapper1_count, 3u);
}

// Tests that we can match timestamps on delivered messages.  By doing this in
// the reverse order, the second node needs to queue data up from the first node
// to find the matching timestamp.
TEST_F(TimestampMapperTest, ReadNode1First) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config2_.span());

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x006));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(2000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(3000), 0, 0x007));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(3000), 0, chrono::seconds(100)));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});

  ASSERT_EQ(parts[0].logger_node, "pi1");
  ASSERT_EQ(parts[1].logger_node, "pi2");

  size_t mapper0_count = 0;
  TimestampMapper mapper0(FilterPartsForNode(parts, "pi1"));
  mapper0.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper0_count; });
  size_t mapper1_count = 0;
  TimestampMapper mapper1(FilterPartsForNode(parts, "pi2"));
  mapper1.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper1_count; });

  mapper0.AddPeer(&mapper1);
  mapper1.AddPeer(&mapper0);

  {
    SCOPED_TRACE("Trying node1 now");
    std::deque<TimestampedMessage> output1;

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(),
              e + chrono::seconds(100) + chrono::milliseconds(1900));

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(),
              e + chrono::seconds(100) + chrono::milliseconds(2900));

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(), monotonic_clock::max_time);

    ASSERT_TRUE(mapper1.Front() == nullptr);

    EXPECT_EQ(output1[0].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(1000));
    EXPECT_TRUE(output1[0].data.Verify());
    EXPECT_EQ(output1[1].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(2000));
    EXPECT_TRUE(output1[1].data.Verify());
    EXPECT_EQ(output1[2].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(3000));
    EXPECT_TRUE(output1[2].data.Verify());
  }

  {
    std::deque<TimestampedMessage> output0;

    ASSERT_TRUE(mapper0.Front() != nullptr);
    output0.emplace_back(std::move(*mapper0.Front()));
    mapper0.PopFront();
    EXPECT_EQ(mapper0.sorted_until(), monotonic_clock::max_time);

    ASSERT_TRUE(mapper0.Front() != nullptr);
    output0.emplace_back(std::move(*mapper0.Front()));
    mapper0.PopFront();
    EXPECT_EQ(mapper0.sorted_until(), monotonic_clock::max_time);

    ASSERT_TRUE(mapper0.Front() != nullptr);
    output0.emplace_back(std::move(*mapper0.Front()));
    mapper0.PopFront();
    EXPECT_EQ(mapper0.sorted_until(), monotonic_clock::max_time);

    ASSERT_TRUE(mapper0.Front() == nullptr);

    EXPECT_EQ(output0[0].monotonic_event_time, e + chrono::milliseconds(1000));
    EXPECT_TRUE(output0[0].data.Verify());
    EXPECT_EQ(output0[1].monotonic_event_time, e + chrono::milliseconds(2000));
    EXPECT_TRUE(output0[1].data.Verify());
    EXPECT_EQ(output0[2].monotonic_event_time, e + chrono::milliseconds(3000));
    EXPECT_TRUE(output0[2].data.Verify());
  }

  EXPECT_EQ(mapper0_count, 3u);
  EXPECT_EQ(mapper1_count, 3u);
}

// Tests that we return just the timestamps if we couldn't find the data and the
// missing data was at the beginning of the file.
TEST_F(TimestampMapperTest, ReadMissingDataBefore) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config2_.span());

    MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005);
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x006));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(2000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(3000), 0, 0x007));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(3000), 0, chrono::seconds(100)));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});

  ASSERT_EQ(parts[0].logger_node, "pi1");
  ASSERT_EQ(parts[1].logger_node, "pi2");

  size_t mapper0_count = 0;
  TimestampMapper mapper0(FilterPartsForNode(parts, "pi1"));
  mapper0.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper0_count; });
  size_t mapper1_count = 0;
  TimestampMapper mapper1(FilterPartsForNode(parts, "pi2"));
  mapper1.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper1_count; });

  mapper0.AddPeer(&mapper1);
  mapper1.AddPeer(&mapper0);

  {
    SCOPED_TRACE("Trying node1 now");
    std::deque<TimestampedMessage> output1;

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(),
              e + chrono::seconds(100) + chrono::milliseconds(1900));

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(),
              e + chrono::seconds(100) + chrono::milliseconds(2900));

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(), monotonic_clock::max_time);

    ASSERT_TRUE(mapper1.Front() == nullptr);

    EXPECT_EQ(output1[0].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(1000));
    EXPECT_FALSE(output1[0].data.Verify());
    EXPECT_EQ(output1[1].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(2000));
    EXPECT_TRUE(output1[1].data.Verify());
    EXPECT_EQ(output1[2].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(3000));
    EXPECT_TRUE(output1[2].data.Verify());
  }

  EXPECT_EQ(mapper0_count, 0u);
  EXPECT_EQ(mapper1_count, 3u);
}

// Tests that we return just the timestamps if we couldn't find the data and the
// missing data was at the end of the file.
TEST_F(TimestampMapperTest, ReadMissingDataAfter) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config2_.span());

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x006));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(2000), 0, chrono::seconds(100)));

    MakeLogMessage(e + chrono::milliseconds(3000), 0, 0x007);
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(3000), 0, chrono::seconds(100)));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});

  ASSERT_EQ(parts[0].logger_node, "pi1");
  ASSERT_EQ(parts[1].logger_node, "pi2");

  size_t mapper0_count = 0;
  TimestampMapper mapper0(FilterPartsForNode(parts, "pi1"));
  mapper0.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper0_count; });
  size_t mapper1_count = 0;
  TimestampMapper mapper1(FilterPartsForNode(parts, "pi2"));
  mapper1.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper1_count; });

  mapper0.AddPeer(&mapper1);
  mapper1.AddPeer(&mapper0);

  {
    SCOPED_TRACE("Trying node1 now");
    std::deque<TimestampedMessage> output1;

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(),
              e + chrono::seconds(100) + chrono::milliseconds(1900));

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(),
              e + chrono::seconds(100) + chrono::milliseconds(2900));

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    EXPECT_EQ(mapper1.sorted_until(), monotonic_clock::max_time);

    ASSERT_TRUE(mapper1.Front() == nullptr);

    EXPECT_EQ(output1[0].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(1000));
    EXPECT_TRUE(output1[0].data.Verify());
    EXPECT_EQ(output1[1].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(2000));
    EXPECT_TRUE(output1[1].data.Verify());
    EXPECT_EQ(output1[2].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(3000));
    EXPECT_FALSE(output1[2].data.Verify());
  }

  EXPECT_EQ(mapper0_count, 0u);
  EXPECT_EQ(mapper1_count, 3u);
}

// Tests that we handle a message which failed to forward or be logged.
TEST_F(TimestampMapperTest, ReadMissingDataMiddle) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config2_.span());

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100)));

    // Create both the timestamp and message, but don't log them, simulating a
    // forwarding drop.
    MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x006);
    MakeTimestampMessage(e + chrono::milliseconds(2000), 0,
                         chrono::seconds(100));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(3000), 0, 0x007));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(3000), 0, chrono::seconds(100)));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});

  ASSERT_EQ(parts[0].logger_node, "pi1");
  ASSERT_EQ(parts[1].logger_node, "pi2");

  size_t mapper0_count = 0;
  TimestampMapper mapper0(FilterPartsForNode(parts, "pi1"));
  mapper0.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper0_count; });
  size_t mapper1_count = 0;
  TimestampMapper mapper1(FilterPartsForNode(parts, "pi2"));
  mapper1.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper1_count; });

  mapper0.AddPeer(&mapper1);
  mapper1.AddPeer(&mapper0);

  {
    std::deque<TimestampedMessage> output1;

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));

    ASSERT_FALSE(mapper1.Front() == nullptr);

    EXPECT_EQ(output1[0].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(1000));
    EXPECT_TRUE(output1[0].data.Verify());
    EXPECT_EQ(output1[1].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(3000));
    EXPECT_TRUE(output1[1].data.Verify());
  }

  EXPECT_EQ(mapper0_count, 0u);
  EXPECT_EQ(mapper1_count, 2u);
}

// Tests that we properly sort log files with duplicate timestamps.
TEST_F(TimestampMapperTest, ReadSameTimestamp) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config2_.span());

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x006));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(2000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x007));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(2000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(3000), 0, 0x008));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(3000), 0, chrono::seconds(100)));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});

  ASSERT_EQ(parts[0].logger_node, "pi1");
  ASSERT_EQ(parts[1].logger_node, "pi2");

  size_t mapper0_count = 0;
  TimestampMapper mapper0(FilterPartsForNode(parts, "pi1"));
  mapper0.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper0_count; });
  size_t mapper1_count = 0;
  TimestampMapper mapper1(FilterPartsForNode(parts, "pi2"));
  mapper1.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper1_count; });

  mapper0.AddPeer(&mapper1);
  mapper1.AddPeer(&mapper0);

  {
    SCOPED_TRACE("Trying node1 now");
    std::deque<TimestampedMessage> output1;

    for (int i = 0; i < 4; ++i) {
      ASSERT_TRUE(mapper1.Front() != nullptr);
      output1.emplace_back(std::move(*mapper1.Front()));
      mapper1.PopFront();
    }
    ASSERT_TRUE(mapper1.Front() == nullptr);

    EXPECT_EQ(output1[0].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(1000));
    EXPECT_TRUE(output1[0].data.Verify());
    EXPECT_EQ(output1[1].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(2000));
    EXPECT_TRUE(output1[1].data.Verify());
    EXPECT_EQ(output1[2].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(2000));
    EXPECT_TRUE(output1[2].data.Verify());
    EXPECT_EQ(output1[3].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(3000));
    EXPECT_TRUE(output1[3].data.Verify());
  }

  EXPECT_EQ(mapper0_count, 0u);
  EXPECT_EQ(mapper1_count, 4u);
}

// Tests that we properly sort log files with duplicate timestamps.
TEST_F(TimestampMapperTest, StartTime) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config1_.span());
    DetachedBufferWriter writer2(logfile2_, std::make_unique<DummyEncoder>());
    writer2.QueueSpan(config3_.span());
  }

  const std::vector<LogFile> parts =
      SortParts({logfile0_, logfile1_, logfile2_});

  size_t mapper0_count = 0;
  TimestampMapper mapper0(FilterPartsForNode(parts, "pi1"));
  mapper0.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper0_count; });

  EXPECT_EQ(mapper0.monotonic_start_time(), e + chrono::milliseconds(1));
  EXPECT_EQ(mapper0.realtime_start_time(),
            realtime_clock::time_point(chrono::seconds(1000)));
  EXPECT_EQ(mapper0_count, 0u);
}

// Tests that when a peer isn't registered, we treat that as if there was no
// data available.
TEST_F(TimestampMapperTest, NoPeer) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config2_.span());

    MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005);
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x006));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(2000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(3000), 0, 0x007));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(3000), 0, chrono::seconds(100)));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});

  ASSERT_EQ(parts[0].logger_node, "pi1");
  ASSERT_EQ(parts[1].logger_node, "pi2");

  size_t mapper1_count = 0;
  TimestampMapper mapper1(FilterPartsForNode(parts, "pi2"));
  mapper1.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper1_count; });

  {
    std::deque<TimestampedMessage> output1;

    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    ASSERT_TRUE(mapper1.Front() == nullptr);

    EXPECT_EQ(output1[0].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(1000));
    EXPECT_FALSE(output1[0].data.Verify());
    EXPECT_EQ(output1[1].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(2000));
    EXPECT_FALSE(output1[1].data.Verify());
    EXPECT_EQ(output1[2].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(3000));
    EXPECT_FALSE(output1[2].data.Verify());
  }
  EXPECT_EQ(mapper1_count, 3u);
}

// Tests that we can queue messages and call the timestamp callback for both
// nodes.
TEST_F(TimestampMapperTest, QueueUntilNode0) {
  const aos::monotonic_clock::time_point e = monotonic_clock::epoch();
  {
    DetachedBufferWriter writer0(logfile0_, std::make_unique<DummyEncoder>());
    writer0.QueueSpan(config0_.span());
    DetachedBufferWriter writer1(logfile1_, std::make_unique<DummyEncoder>());
    writer1.QueueSpan(config2_.span());

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x005));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(1000), 0, 0x006));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(1000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(2000), 0, 0x007));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(2000), 0, chrono::seconds(100)));

    writer0.QueueSizedFlatbuffer(
        MakeLogMessage(e + chrono::milliseconds(3000), 0, 0x008));
    writer1.QueueSizedFlatbuffer(MakeTimestampMessage(
        e + chrono::milliseconds(3000), 0, chrono::seconds(100)));
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});

  ASSERT_EQ(parts[0].logger_node, "pi1");
  ASSERT_EQ(parts[1].logger_node, "pi2");

  size_t mapper0_count = 0;
  TimestampMapper mapper0(FilterPartsForNode(parts, "pi1"));
  mapper0.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper0_count; });
  size_t mapper1_count = 0;
  TimestampMapper mapper1(FilterPartsForNode(parts, "pi2"));
  mapper1.set_timestamp_callback(
      [&](TimestampedMessage *) { ++mapper1_count; });

  mapper0.AddPeer(&mapper1);
  mapper1.AddPeer(&mapper0);

  {
    std::deque<TimestampedMessage> output0;

    EXPECT_EQ(mapper0_count, 0u);
    EXPECT_EQ(mapper1_count, 0u);
    mapper0.QueueUntil(e + chrono::milliseconds(1000));
    EXPECT_EQ(mapper0_count, 3u);
    EXPECT_EQ(mapper1_count, 0u);

    ASSERT_TRUE(mapper0.Front() != nullptr);
    EXPECT_EQ(mapper0_count, 3u);
    EXPECT_EQ(mapper1_count, 0u);

    mapper0.QueueUntil(e + chrono::milliseconds(1500));
    EXPECT_EQ(mapper0_count, 3u);
    EXPECT_EQ(mapper1_count, 0u);

    mapper0.QueueUntil(e + chrono::milliseconds(2500));
    EXPECT_EQ(mapper0_count, 4u);
    EXPECT_EQ(mapper1_count, 0u);

    output0.emplace_back(std::move(*mapper0.Front()));
    mapper0.PopFront();
    output0.emplace_back(std::move(*mapper0.Front()));
    mapper0.PopFront();
    output0.emplace_back(std::move(*mapper0.Front()));
    mapper0.PopFront();
    output0.emplace_back(std::move(*mapper0.Front()));
    mapper0.PopFront();

    EXPECT_EQ(mapper0_count, 4u);
    EXPECT_EQ(mapper1_count, 0u);

    ASSERT_TRUE(mapper0.Front() == nullptr);

    EXPECT_EQ(output0[0].monotonic_event_time, e + chrono::milliseconds(1000));
    EXPECT_TRUE(output0[0].data.Verify());
    EXPECT_EQ(output0[1].monotonic_event_time, e + chrono::milliseconds(1000));
    EXPECT_TRUE(output0[1].data.Verify());
    EXPECT_EQ(output0[2].monotonic_event_time, e + chrono::milliseconds(2000));
    EXPECT_TRUE(output0[2].data.Verify());
    EXPECT_EQ(output0[3].monotonic_event_time, e + chrono::milliseconds(3000));
    EXPECT_TRUE(output0[3].data.Verify());
  }

  {
    SCOPED_TRACE("Trying node1 now");
    std::deque<TimestampedMessage> output1;

    EXPECT_EQ(mapper0_count, 4u);
    EXPECT_EQ(mapper1_count, 0u);
    mapper1.QueueUntil(e + chrono::seconds(100) + chrono::milliseconds(1000));
    EXPECT_EQ(mapper0_count, 4u);
    EXPECT_EQ(mapper1_count, 3u);

    ASSERT_TRUE(mapper1.Front() != nullptr);
    EXPECT_EQ(mapper0_count, 4u);
    EXPECT_EQ(mapper1_count, 3u);

    mapper1.QueueUntil(e + chrono::seconds(100) + chrono::milliseconds(1500));
    EXPECT_EQ(mapper0_count, 4u);
    EXPECT_EQ(mapper1_count, 3u);

    mapper1.QueueUntil(e + chrono::seconds(100) + chrono::milliseconds(2500));
    EXPECT_EQ(mapper0_count, 4u);
    EXPECT_EQ(mapper1_count, 4u);

    ASSERT_TRUE(mapper1.Front() != nullptr);
    EXPECT_EQ(mapper0_count, 4u);
    EXPECT_EQ(mapper1_count, 4u);

    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();
    ASSERT_TRUE(mapper1.Front() != nullptr);
    output1.emplace_back(std::move(*mapper1.Front()));
    mapper1.PopFront();

    EXPECT_EQ(mapper0_count, 4u);
    EXPECT_EQ(mapper1_count, 4u);

    ASSERT_TRUE(mapper1.Front() == nullptr);

    EXPECT_EQ(mapper0_count, 4u);
    EXPECT_EQ(mapper1_count, 4u);

    EXPECT_EQ(output1[0].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(1000));
    EXPECT_TRUE(output1[0].data.Verify());
    EXPECT_EQ(output1[1].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(1000));
    EXPECT_TRUE(output1[1].data.Verify());
    EXPECT_EQ(output1[2].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(2000));
    EXPECT_TRUE(output1[2].data.Verify());
    EXPECT_EQ(output1[3].monotonic_event_time,
              e + chrono::seconds(100) + chrono::milliseconds(3000));
    EXPECT_TRUE(output1[3].data.Verify());
  }
}

// This tests that we can properly sort a multi-node log file which has the old
// (and buggy) timestamps in the header, and the non-resetting parts_index.
// These make it so we can just bairly figure out what happened first and what
// happened second, but not in a way that is robust to multiple nodes rebooting.
TEST_F(SortingElementTest, OldReboot) {
  const aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> boot0 =
      MakeHeader(config_, R"({
  /* 100ms */
  "max_out_of_order_duration": 100000000,
  "node": {
    "name": "pi2"
  },
  "logger_node": {
    "name": "pi1"
  },
  "monotonic_start_time": 1000000,
  "realtime_start_time": 1000000000000,
  "logger_monotonic_start_time": 1000000,
  "logger_realtime_start_time": 1000000000000,
  "log_event_uuid": "30ef1283-81d7-4004-8c36-1c162dbcb2b2",
  "parts_uuid": "1a9e5ca2-31b2-475b-8282-88f6d1ce5109",
  "parts_index": 0,
  "logger_instance_uuid": "1c3142ad-10a5-408d-a760-b63b73d3b904",
  "logger_node_boot_uuid": "a570df8b-5cc2-4dbe-89bd-286f9ddd02b7",
  "source_node_boot_uuid": "6ba4f28d-21a2-4d7f-83f4-ee365cf86464"
})");
  const aos::SizePrefixedFlatbufferDetachedBuffer<LogFileHeader> boot1 =
      MakeHeader(config_, R"({
  /* 100ms */
  "max_out_of_order_duration": 100000000,
  "node": {
    "name": "pi2"
  },
  "logger_node": {
    "name": "pi1"
  },
  "monotonic_start_time": 1000000,
  "realtime_start_time": 1000000000000,
  "logger_monotonic_start_time": 1000000,
  "logger_realtime_start_time": 1000000000000,
  "log_event_uuid": "30ef1283-81d7-4004-8c36-1c162dbcb2b2",
  "parts_uuid": "2a05d725-5d5c-4c0b-af42-88de2f3c3876",
  "parts_index": 1,
  "logger_instance_uuid": "1c3142ad-10a5-408d-a760-b63b73d3b904",
  "logger_node_boot_uuid": "a570df8b-5cc2-4dbe-89bd-286f9ddd02b7",
  "source_node_boot_uuid": "b728d27a-9181-4eac-bfc1-5d09b80469d2"
})");

  {
    DetachedBufferWriter writer(logfile0_, std::make_unique<DummyEncoder>());
    writer.QueueSpan(boot0.span());
  }
  {
    DetachedBufferWriter writer(logfile1_, std::make_unique<DummyEncoder>());
    writer.QueueSpan(boot1.span());
  }

  const std::vector<LogFile> parts = SortParts({logfile0_, logfile1_});

  ASSERT_EQ(parts.size(), 1u);
  ASSERT_EQ(parts[0].parts.size(), 2u);

  EXPECT_EQ(parts[0].parts[0].boot_count, 0);
  EXPECT_EQ(parts[0].parts[0].source_boot_uuid,
            boot0.message().source_node_boot_uuid()->string_view());

  EXPECT_EQ(parts[0].parts[1].boot_count, 1);
  EXPECT_EQ(parts[0].parts[1].source_boot_uuid,
            boot1.message().source_node_boot_uuid()->string_view());
}

}  // namespace testing
}  // namespace logger
}  // namespace aos