private async Task SendSubscriptionRequest(HttpSubscriptionMetadata subscriptionMetadata, CancellationToken cancellationToken = default(CancellationToken))
{
if (subscriptionMetadata == null)
{
throw new ArgumentNullException(nameof(subscriptionMetadata));
}
var endpoint = subscriptionMetadata.Endpoint;
var topic = subscriptionMetadata.Topic;
var ttl = subscriptionMetadata.TTL;
HttpClient httpClient = null;
HttpResponseMessage httpResponseMessage = null;
try
{
var endpointBaseUri = endpoint.Address.WithTrailingSlash();
httpClient = await _httpClientFactory.GetClient(endpointBaseUri, endpoint.Credentials, cancellationToken);
var urlSafeTopicName = UrlEncoder.Encode(topic);
var relativeUri = $"topic/{urlSafeTopicName}/subscriber?uri={_baseUri}";
if (ttl > TimeSpan.Zero)
{
relativeUri += "&ttl=" + ttl.TotalSeconds;
}
var postUri = new Uri(endpointBaseUri, relativeUri);
httpResponseMessage = await httpClient.PostAsync(relativeUri, new StringContent(""), cancellationToken);
var status = (int?)httpResponseMessage.StatusCode;
await _diagnosticService.EmitAsync(
new HttpEventBuilder(this, HttpEventType.HttpSubscriptionRequestSent)
{
Uri = postUri,
Topic = subscriptionMetadata.Topic,
Status = status
}.Build(), cancellationToken);
HandleHttpErrorResponse(httpResponseMessage);
}
catch (TransportException)
{
throw;
}
catch (TaskCanceledException)
{
throw;
}
catch (Exception ex)
{
var errorMessage =
$"Error sending subscription request for topic {topic} of publisher {endpoint.Address}";
TryHandleCommunicationException(ex, endpoint.Address);
throw new TransportException(errorMessage, ex);
}
finally
{
httpResponseMessage?.Dispose();
httpClient?.Dispose();
}
}
/// <inheritdoc />
public async Task Subscribe(IEndpoint endpoint, TopicName topicName, TimeSpan ttl, CancellationToken cancellationToken = default(CancellationToken))
{
try
{
var subscription = new HttpSubscriptionMetadata(endpoint, topicName, ttl);
while (!cancellationToken.IsCancellationRequested)
{
TimeSpan retryOrRenewAfter;
try
{
await SendSubscriptionRequest(subscription, cancellationToken);
if (!subscription.Expires)
{
// Subscription is not set to expire on the remote server. Since
// publications are pushed to the subscribers, we don't need to keep
// this task running.
return;
}
retryOrRenewAfter = subscription.RenewalInterval;
_diagnosticService.Emit(
new HttpEventBuilder(this, DiagnosticEventType.SubscriptionRenewed)
{
Detail = "Subscription renewed. Next renewal in " + retryOrRenewAfter,
Topic = topicName,
}.Build());
}
catch (EndpointNotFoundException enfe)
{
// Endpoint is not defined in the supplied configuration,
// so we cannot determine the URI. This is an unrecoverable
// error, so simply return.
_diagnosticService.Emit(
new HttpEventBuilder(this, DiagnosticEventType.EndpointNotFound)
{
Detail = "Fatal error sending subscription request: endpoint not found",
Topic = topicName,
Exception = enfe
}.Build());
_diagnosticService.Emit(
new HttpEventBuilder(this, DiagnosticEventType.SubscriptionFailed)
{
Topic = topicName
}.Build());
return;
}
catch (NameResolutionFailedException nrfe)
{
// The transport was unable to resolve the hostname in the
// endpoint URI. This may or may not be a temporary error.
// In either case, retry after 30 seconds.
retryOrRenewAfter = subscription.RetryInterval;
_diagnosticService.Emit(
new HttpEventBuilder(this, HttpEventType.HttpCommunicationError)
{
Detail = "Non-fatal error sending subscription request: unable to resolve address for hostname " + nrfe.Hostname + ". Retry in " + retryOrRenewAfter,
Topic = topicName,
Exception = nrfe
}.Build());
}
catch (ConnectionRefusedException cre)
{
// The transport was unable to resolve the hostname in the
// endpoint URI. This may or may not be a temporary error.
// In either case, retry after 30 seconds.
retryOrRenewAfter = subscription.RetryInterval;
_diagnosticService.Emit(
new HttpEventBuilder(this, HttpEventType.HttpCommunicationError)
{
Detail = "Non-fatal error sending subscription request: connection refused for " + cre.Host + ":" + cre.Port + ". Retry in " + retryOrRenewAfter,
Topic = topicName,
Exception = cre
}.Build());
}
catch (ResourceNotFoundException ire)
{
// Topic is not found. This may be temporary.
retryOrRenewAfter = subscription.RetryInterval;
_diagnosticService.Emit(
new HttpEventBuilder(this, HttpEventType.HttpCommunicationError)
{
Detail = "Non-fatal error sending subscription request: resource not found. Topic may be misconfigured. Retry in " + retryOrRenewAfter,
Topic = topicName,
Exception = ire
}.Build());
}
catch (InvalidRequestException ire)
{
// Request is not valid. Either the URL is malformed or the
// topic does not exist. In any case, retrying would be
// fruitless, so just return.
_diagnosticService.Emit(
new HttpEventBuilder(this, DiagnosticEventType.EndpointNotFound)
{
Detail = "Fatal error sending subscription request: invalid request. Subscription abandoned.",
Topic = topicName,
Exception = ire
}.Build());
_diagnosticService.Emit(
new HttpEventBuilder(this, DiagnosticEventType.SubscriptionFailed)
{
Topic = topicName
}.Build());
return;
}
catch (TransportException te)
{
// Unspecified transport error. This may or may not be
// due to temporary conditions that will resolve
// themselves. Retry in 30 seconds.
retryOrRenewAfter = subscription.RetryInterval;
_diagnosticService.Emit(
new HttpEventBuilder(this, HttpEventType.HttpCommunicationError)
{
Detail = "Non-fatal error sending subscription request: communication error. Retry in " + retryOrRenewAfter,
Topic = topicName,
Exception = te
}.Build());
}
await Task.Delay(retryOrRenewAfter, cancellationToken);
}
}
catch (OperationCanceledException)
{
}
}