public Func <IChangeToken> Build(out IDisposable factoryLifetime)
{
var disposables = _disposables.ToArray(); // capture snapshot.
factoryLifetime = new InvokeOnDispose(() =>
{
foreach (var item in disposables)
{
item?.Dispose();
}
});
if (Factories == null || Factories.Count == 0)
{
return(() => EmptyChangeToken.Instance);
}
if (Factories.Count == 1)
{
return(Factories[0]); // pass through - no need to build composite for single producer.
}
var factories = Factories.ToArray(); // capture snapshot
Reset(); // so builder is empty again to build another.
return(() =>
{
var tokens = new IChangeToken[factories.Length];
for (var i = 0; i < factories.Length; i++)
{
tokens[i] = factories[i].Invoke();
}
return new CompositeChangeToken(tokens);
});
}
/// <summary>
/// Adds <see cref="ReloadPipelineMiddleware"/> to the middleware pipeline, with a change token to invalidate it and rebuild it whenever <typeparamref name="TOptions"/> changes.
/// </summary>
/// <typeparam name="TOptions"></typeparam>
/// <param name="builder"></param>
/// <param name="configure"></param>
/// <param name="isTerminal"></param>
/// <returns></returns>
/// <remarks>You must ensure <typeparamref name="TOptions"/></remarks> has been registered with the options system in ConfigureServices.
private static IApplicationBuilder AddReloadablePipeline <TOptions>(this IApplicationBuilder builder, Action <IApplicationBuilder, IWebHostEnvironment, TOptions> configure, bool isTerminal)
where TOptions : class
{
var env = builder.ApplicationServices.GetRequiredService <IWebHostEnvironment>();
var monitor = builder.ApplicationServices.GetRequiredService <IOptionsMonitor <TOptions> >();
IDisposable previousRegistration = null;
var factory = new RequestDelegateFactory(env, () =>
{
// When should ensure any previous CancellationTokenSource is disposed,
// and we remove old monitor OnChange listener, before creating new ones.
previousRegistration?.Dispose();
var changeTokenSource = new CancellationTokenSource();
var monitorListener = monitor.OnChange(a => changeTokenSource.Cancel());
previousRegistration = new InvokeOnDispose(() =>
{
// Ensure disposal of listener and token source that we created.
monitorListener.Dispose();
changeTokenSource.Dispose();
});
var changeToken = new CancellationChangeToken(changeTokenSource.Token);
return(changeToken);
}, (a, b) =>
{
configure(a, b, monitor.CurrentValue);
});
builder.UseMiddleware <ReloadPipelineMiddleware>(builder, factory, isTerminal);
return(builder);
}
public static Func <IChangeToken> UseCallbackRegistrations(Func <Action, IDisposable> registerListener)
{
IDisposable previousRegistration = null;
Func <IChangeToken> changeTokenFactory = () =>
{
// When should ensure any previous CancellationTokenSource is disposed,
// and we remove old monitor OnChange listener, before creating new ones.
previousRegistration?.Dispose();
var changeTokenSource = new CancellationTokenSource();
var disposable = registerListener(() => changeTokenSource.Cancel());
previousRegistration = new InvokeOnDispose(() =>
{
// Ensure disposal of listener and token source that we created.
disposable.Dispose();
changeTokenSource.Dispose();
});
var changeToken = new CancellationChangeToken(changeTokenSource.Token);
return(changeToken);
};
return(changeTokenFactory);
}
