/// <summary>
/// Builds a bulkhead isolation <see cref="Policy" />, which limits the maximum concurrency of actions executed through the policy. Imposing a maximum concurrency limits the potential of governed actions, when faulting, to bring down the system.
/// <para>When an execution would cause the number of actions executing concurrently through the policy to exceed <paramref name="maxParallelization" />, the policy allows a further <paramref name="maxQueuingActions" /> executions to queue, waiting for a concurrent execution slot. When an execution would cause the number of queuing actions to exceed <paramref name="maxQueuingActions" />, a <see cref="BulkheadRejectedException" /> is thrown.</para>
/// </summary>
/// <param name="maxParallelization">The maximum number of concurrent actions that may be executing through the policy.</param>
/// <param name="maxQueuingActions">The maximum number of actions that may be queuing, waiting for an execution slot.</param>
/// <param name="onBulkheadRejectedAsync">An action to call asynchronously, if the bulkhead rejects execution due to oversubscription.</param>
/// <returns>The policy instance.</returns>
/// <exception cref="System.ArgumentOutOfRangeException">maxParallelization;Value must be greater than zero.</exception>
/// <exception cref="System.ArgumentOutOfRangeException">maxQueuingActions;Value must be greater than or equal to zero.</exception>
/// <exception cref="System.ArgumentNullException">onBulkheadRejectedAsync</exception>
public static BulkheadPolicy BulkheadAsync(int maxParallelization, int maxQueuingActions, Func <Context, Task> onBulkheadRejectedAsync)
{
if (maxParallelization <= 0)
{
throw new ArgumentOutOfRangeException(nameof(maxParallelization), "Value must be greater than zero.");
}
if (maxQueuingActions < 0)
{
throw new ArgumentOutOfRangeException(nameof(maxQueuingActions), "Value must be greater than or equal to zero.");
}
if (onBulkheadRejectedAsync == null)
{
throw new ArgumentNullException(nameof(onBulkheadRejectedAsync));
}
SemaphoreSlim maxParallelizationSemaphore = SemaphoreSlimFactory.CreateSemaphoreSlim(maxParallelization);
var maxQueuingCompounded = maxQueuingActions <= int.MaxValue - maxParallelization
? maxQueuingActions + maxParallelization
: int.MaxValue;
SemaphoreSlim maxQueuedActionsSemaphore = SemaphoreSlimFactory.CreateSemaphoreSlim(maxQueuingCompounded);
return(new BulkheadPolicy((action, context, cancellationToken, continueOnCapturedContext) =>
BulkheadEngine.ImplementationAsync(
async(ctx, ct) => { await action(ctx, ct).ConfigureAwait(continueOnCapturedContext); return EmptyStruct.Instance; },
context,
onBulkheadRejectedAsync,
maxParallelizationSemaphore,
maxQueuedActionsSemaphore,
cancellationToken,
continueOnCapturedContext),
maxParallelization,
maxQueuingActions,
maxParallelizationSemaphore,
maxQueuedActionsSemaphore
));
}
/// <summary>
/// Builds a bulkhead isolation <see cref="Policy" />, which limits the maximum concurrency of actions executed through the policy. Imposing a maximum concurrency limits the potential of governed actions, when faulting, to bring down the system.
/// <para>When an execution would cause the number of actions executing concurrently through the policy to exceed <paramref name="maxParallelization" />, the policy allows a further <paramref name="maxQueuingActions" /> executions to queue, waiting for a concurrent execution slot. When an execution would cause the number of queuing actions to exceed <paramref name="maxQueuingActions" />, a <see cref="BulkheadRejectedException" /> is thrown.</para>
/// </summary>
/// <param name="maxParallelization">The maximum number of concurrent actions that may be executing through the policy.</param>
/// <param name="maxQueuingActions">The maxmimum number of actions that may be queuing, waiting for an execution slot.</param>
/// <param name="onBulkheadRejectedAsync">An action to call asynchronously, if the bulkhead rejects execution due to oversubscription.</param>
/// <returns>The policy instance.</returns>
/// <exception cref="System.ArgumentOutOfRangeException">maxParallelization;Value must be greater than zero.</exception>
/// <exception cref="System.ArgumentOutOfRangeException">maxQueuingActions;Value must be greater than or equal to zero.</exception>
/// <exception cref="System.ArgumentNullException">onBulkheadRejectedAsync</exception>
public static BulkheadPolicy <TResult> BulkheadAsync <TResult>(int maxParallelization, int maxQueuingActions, Func <Context, Task> onBulkheadRejectedAsync)
{
if (maxParallelization <= 0)
{
throw new ArgumentOutOfRangeException(nameof(maxParallelization), "Value must be greater than zero.");
}
if (maxQueuingActions < 0)
{
throw new ArgumentOutOfRangeException(nameof(maxQueuingActions), "Value must be greater than or equal to zero.");
}
if (onBulkheadRejectedAsync == null)
{
throw new ArgumentNullException(nameof(onBulkheadRejectedAsync));
}
SemaphoreSlim maxParallelizationSemaphore = new SemaphoreSlim(maxParallelization, maxParallelization);
var maxQueuingCompounded = maxQueuingActions <= int.MaxValue - maxParallelization
? maxQueuingActions + maxParallelization
: int.MaxValue;
SemaphoreSlim maxQueuedActionsSemaphore = new SemaphoreSlim(maxQueuingCompounded, maxQueuingCompounded);
return(new BulkheadPolicy <TResult>(
(action, context, cancellationToken, continueOnCapturedContext) => BulkheadEngine.ImplementationAsync(
action,
context,
onBulkheadRejectedAsync,
maxParallelizationSemaphore,
maxQueuedActionsSemaphore,
cancellationToken,
continueOnCapturedContext),
maxParallelization,
maxQueuingActions,
maxParallelizationSemaphore,
maxQueuedActionsSemaphore
));
}