public void GetDatabaseTimeCached_BestLatency()
{
var tests = new ListOfTuples <ListOfTuples <int, double>, int>
{
// Format: 3 x (db latency ms, db clock offset seconds) => expected clock offset
{ new ListOfTuples <int, double> {
{ 20, 11 }, { 30, 22 }, { 40, 33 }
}, 11 },
{ new ListOfTuples <int, double> {
{ 40, 11 }, { 20, 22 }, { 30, 33 }
}, 22 },
{ new ListOfTuples <int, double> {
{ 40, 11 }, { 30, 22 }, { 20, 33 }
}, 33 },
};
for (int t = 0; t < tests.Count(); t++)
{
var test = tests[t];
var dbUsage = new List <bool>();
TimeSpan lastDbOffset = TimeSpan.MaxValue;
DatabaseTimeCache.Reset();
DateTime systemTime = new DateTime(2001, 2, 3, 4, 5, 6);
foreach (var sqlClock in test.Item1.Concat(new[] { Tuple.Create <int, double>(70, 70) }))
{
DateTime dbTime = DateTime.MinValue;
bool dbRead = false;
DateTime computed = DatabaseTimeCache.GetDatabaseTimeCached(
() =>
{
dbRead = true;
// There is no need to use Thred.Sleep(sqlClock.Item1) here, because db latency is simulated by increasing the systemTime value.
return(dbTime = systemTime.AddSeconds(sqlClock.Item2));
},
() =>
{
return(systemTime = systemTime.AddMilliseconds(sqlClock.Item1));
});
dbUsage.Add(dbRead);
lastDbOffset = computed.Subtract(systemTime);
Console.WriteLine($"Test {t} {sqlClock.Item1} {sqlClock.Item2}: sys {systemTime.ToString("o")}, db {dbTime.ToString("o")} " +
$"=> {ReportDbOrCache(dbRead)} {computed.ToString("o")}");
}
Assert.AreEqual("read db, read db, read db, read cache", TestUtility.Dump(dbUsage, ReportDbOrCache),
$"Test {t}: Should use cache after 3rd query from database.");
Assert.AreEqual(test.Item2, Convert.ToInt32(lastDbOffset.TotalSeconds),
$"Test {t}: When using datetime cache, the database offset should be the one taken with the smallest latency.");
}
}
private void RunTests(DateTime baseSysTime, TimeSpan dbOffset, ListOfTuples <int, double, bool> tests)
{
DatabaseTimeCache.Reset();
foreach (var test in tests)
{
DateTime systemTime = baseSysTime.AddMinutes(test.Item1).AddSeconds(test.Item2);
DateTime dbTime = systemTime.Add(dbOffset);
bool dbRead = false;
DateTime computed = DatabaseTimeCache.GetDatabaseTimeCached(() => { dbRead = true; return(dbTime); }, () => systemTime);
string report = $"Test {test.Item1} {test.Item2}: sys {systemTime.ToString("o")}, db {dbTime.ToString("o")} " +
$"=> {ReportDbOrCache(dbRead)} {computed.ToString("o")}";
Console.WriteLine(report);
Assert.AreEqual(ReportDbOrCache(test.Item3), ReportDbOrCache(dbRead), report);
Assert.AreEqual(dbTime, computed, report);
}
}