private async Task ListeningThread(string host, Func <ICommand, Task> handlerAsync, Func <ICommand, Task> handlerAwaitAsync)
{
canceller = new CancellationTokenSource();
retry:
IConsumer <string, byte[]> consumer = null;
try
{
await KafkaCommon.AssureTopic(host, topic);
var consumerConfig = new ConsumerConfig();
consumerConfig.BootstrapServers = host;
consumerConfig.GroupId = topic;
consumerConfig.EnableAutoCommit = false;
consumer = new ConsumerBuilder <string, byte[]>(consumerConfig).Build();
consumer.Subscribe(topic);
for (; ;)
{
Exception error = null;
bool awaitResponse = false;
string ackTopic = null;
string ackKey = null;
try
{
if (canceller.Token.IsCancellationRequested)
{
break;
}
var consumerResult = consumer.Consume(canceller.Token);
consumer.Commit(consumerResult);
awaitResponse = consumerResult.Message.Key == KafkaCommon.MessageWithAckKey;
if (awaitResponse)
{
ackTopic = Encoding.UTF8.GetString(consumerResult.Message.Headers.GetLastBytes(KafkaCommon.AckTopicHeader));
ackKey = Encoding.UTF8.GetString(consumerResult.Message.Headers.GetLastBytes(KafkaCommon.AckKeyHeader));
}
if (consumerResult.Message.Key == KafkaCommon.MessageKey || awaitResponse)
{
var stopwatch = new Stopwatch();
stopwatch.Start();
byte[] body = consumerResult.Message.Value;
if (encryptionKey != null)
{
body = SymmetricEncryptor.Decrypt(encryptionAlgorithm, encryptionKey, body);
}
var message = KafkaCommon.Deserialize <KafkaCommandMessage>(body);
if (message.Claims != null)
{
var claimsIdentity = new ClaimsIdentity(message.Claims.Select(x => new Claim(x[0], x[1])), "CQRS");
Thread.CurrentPrincipal = new ClaimsPrincipal(claimsIdentity);
}
if (awaitResponse)
{
await handlerAwaitAsync(message.Message);
}
else
{
await handlerAsync(message.Message);
}
stopwatch.Stop();
_ = Log.TraceAsync($"Received Await: {topic} {stopwatch.ElapsedMilliseconds}");
}
else
{
_ = Log.ErrorAsync($"{nameof(KafkaServer)} unrecognized message key {consumerResult.Message.Key}");
}
}
catch (TaskCanceledException)
{
break;
}
catch (Exception ex)
{
_ = Log.TraceAsync($"Error: Received Await: {topic}");
_ = Log.ErrorAsync(ex);
error = ex;
}
if (awaitResponse)
{
IProducer <string, byte[]> producer = null;
try
{
var producerConfig = new ProducerConfig();
producerConfig.BootstrapServers = host;
producerConfig.ClientId = clientID;
producer = new ProducerBuilder <string, byte[]>(producerConfig).Build();
var ack = new Acknowledgement()
{
Success = error == null,
ErrorMessage = error?.Message
};
var body = KafkaCommon.Serialize(ack);
if (encryptionKey != null)
{
body = SymmetricEncryptor.Encrypt(encryptionAlgorithm, encryptionKey, body);
}
await producer.ProduceAsync(ackTopic, new Message <string, byte[]>() { Key = ackKey, Value = body });
}
catch (Exception ex)
{
_ = Log.ErrorAsync(ex);
}
finally
{
if (producer != null)
{
producer.Dispose();
}
}
}
}
consumer.Unsubscribe();
}
catch (Exception ex)
{
_ = Log.ErrorAsync(ex);
if (consumer != null)
{
consumer.Dispose();
}
consumer = null;
if (!canceller.IsCancellationRequested)
{
await Task.Delay(retryDelay);
goto retry;
}
}
canceller.Dispose();
canceller = null;
if (consumer != null)
{
consumer.Dispose();
}
IsOpen = false;
}
private async Task SendAsync(ICommand command, bool requireAcknowledgement)
{
if (requireAcknowledgement)
{
if (!listenerStarted)
{
await listenerStartedLock.WaitAsync();
if (!listenerStarted)
{
_ = Task.Run(AckListeningThread);
listenerStarted = true;
}
listenerStartedLock.Release();
}
}
var topic = command.GetType().GetNiceName();
string[][] claims = null;
if (Thread.CurrentPrincipal is ClaimsPrincipal principal)
{
claims = principal.Claims.Select(x => new string[] { x.Type, x.Value }).ToArray();
}
var message = new KafkaCommandMessage()
{
Message = command,
Claims = claims
};
var body = KafkaCommon.Serialize(message);
if (encryptionKey != null)
{
body = SymmetricEncryptor.Encrypt(encryptionAlgorithm, encryptionKey, body);
}
if (requireAcknowledgement)
{
var ackKey = Guid.NewGuid().ToString();
var headers = new Headers();
headers.Add(new Header(KafkaCommon.AckTopicHeader, Encoding.UTF8.GetBytes(ackTopic)));
headers.Add(new Header(KafkaCommon.AckKeyHeader, Encoding.UTF8.GetBytes(ackKey)));
var key = KafkaCommon.MessageWithAckKey;
var waiter = new SemaphoreSlim(0, 1);
try
{
Acknowledgement ack = null;
ackCallbacks.TryAdd(ackKey, (ackFromCallback) =>
{
ack = ackFromCallback;
waiter.Release();
});
var producerResult = await producer.ProduceAsync(topic, new Message <string, byte[]> {
Headers = headers, Key = key, Value = body
});
if (producerResult.Status != PersistenceStatus.Persisted)
{
throw new Exception($"{nameof(KafkaClient)} failed: {producerResult.Status}");
}
await waiter.WaitAsync();
if (!ack.Success)
{
throw new AcknowledgementException(ack, topic);
}
}
finally
{
if (waiter != null)
{
waiter.Dispose();
}
}
}
else
{
var key = KafkaCommon.MessageKey;
var producerResult = await producer.ProduceAsync(topic, new Message <string, byte[]> {
Key = key, Value = body
});
if (producerResult.Status != PersistenceStatus.Persisted)
{
throw new Exception($"{nameof(KafkaClient)} failed: {producerResult.Status}");
}
}
}
