public async Task GetRequiredService_ResolvingSameSingletonInTwoThreads_SameServiceReturned()
{
using (var mreForThread1 = new ManualResetEvent(false))
using (var mreForThread2 = new ManualResetEvent(false))
using (var mreForThread3 = new ManualResetEvent(false))
{
InnerSingleton innerSingleton = null;
OuterSingleton outerSingleton = null;
IServiceProvider sp = null;
// Arrange
var services = new ServiceCollection();
services.AddSingleton <OuterSingleton>();
services.AddSingleton(sp => new InnerSingleton(mreForThread1, mreForThread2));
sp = services.BuildServiceProvider();
var t1 = Task.Run(() =>
{
outerSingleton = sp.GetRequiredService <OuterSingleton>();
});
// Wait until mre2 gets set in InnerSingleton ctor
mreForThread2.WaitOne();
var t2 = Task.Run(() =>
{
mreForThread3.Set();
// This waits on InnerSingleton singleton lock that is taken in thread 1
innerSingleton = sp.GetRequiredService <InnerSingleton>();
});
mreForThread3.WaitOne();
// Set a timeout before unblocking execution of both thread1 and thread2 via mre1:
Assert.False(mreForThread1.WaitOne(10));
// By this time thread 1 has already reached InnerSingleton ctor and is waiting for mre1.
// within the GetRequiredService call, thread 2 should be waiting on a singleton lock for InnerSingleton
// (rather than trying to instantiating InnerSingleton twice).
mreForThread1.Set();
// Act
await t1;
await t2;
// Assert
Assert.NotNull(outerSingleton);
Assert.NotNull(innerSingleton);
Assert.Same(outerSingleton.InnerSingleton, innerSingleton);
}
}
public OuterSingleton(InnerSingleton innerSingleton)
{
InnerSingleton = innerSingleton;
}
