/// <summary>
/// Requests the Server to return a NotificationMessage or a keep-alive Message.
/// </summary>
/// <param name="client">A instance of <see cref="ISessionClient"/>.</param>
/// <param name="request">A <see cref="PublishRequest"/>.</param>
/// <returns>A <see cref="Task"/> representing the asynchronous operation that returns a <see cref="PublishResponse"/>.</returns>
public static async Task<PublishResponse> PublishAsync(this ISessionClient client, PublishRequest request)
{
if (request == null)
{
throw new ArgumentNullException("request");
}
return (PublishResponse)await client.RequestAsync(request).ConfigureAwait(false);
}
/// <summary>
/// Sends publish requests to the server.
/// </summary>
/// <param name="cancellationToken">A cancellation token.</param>
/// <returns>A task.</returns>
private async Task PublishAsync(CancellationToken cancellationToken = default(CancellationToken))
{
var publishRequest = new PublishRequest
{
RequestHeader = new RequestHeader { TimeoutHint = PublishTimeoutHint, ReturnDiagnostics = this.DiagnosticsHint },
SubscriptionAcknowledgements = new SubscriptionAcknowledgement[0]
};
while (!cancellationToken.IsCancellationRequested)
{
try
{
var publishResponse = await this.PublishAsync(publishRequest);
// Views and view models may be abandoned at any time. This code detects when a subscription
// is garbage collected, and deletes the corresponding subscription from the server.
var handled = false;
foreach (var subscription in this.Subscriptions)
{
handled |= subscription.OnPublishResponse(publishResponse);
}
// If event was not handled,
if (!handled)
{
// subscription was garbage collected. So delete from server.
var request = new DeleteSubscriptionsRequest
{
SubscriptionIds = new uint[] { publishResponse.SubscriptionId }
};
await this.DeleteSubscriptionsAsync(request);
}
publishRequest = new PublishRequest
{
RequestHeader = new RequestHeader { TimeoutHint = PublishTimeoutHint, ReturnDiagnostics = this.DiagnosticsHint },
SubscriptionAcknowledgements = new[] { new SubscriptionAcknowledgement { SequenceNumber = publishResponse.NotificationMessage.SequenceNumber, SubscriptionId = publishResponse.SubscriptionId } }
};
}
catch (ServiceResultException ex)
{
Log.Warn($"Error publishing subscription. {ex.Message}");
// short delay, then retry.
await Task.Delay((int)DefaultPublishingInterval);
}
}
}