async Task <SqlConnection> GetOpenConnectionAsync(TriggerListenerOptions options)
{
var connection = new SqlConnection(options.ConnectionString);
if (connection.State == ConnectionState.Closed)
{
await connection.OpenAsync().ConfigureAwait(false);
}
return(connection);
}
void InitializeSqlStatements(TriggerListenerOptions options)
{
var commandBuilder = new SqlCommandBuilder();
var sanitizedQueueName = commandBuilder.QuoteIdentifier(options.QueueName);
_receiveSql = $@"WAITFOR (
RECEIVE TOP({options.MaximumBatchSize})
message_type_name,
CAST(message_body AS XML) AS message_body,
conversation_handle
FROM messaging.{sanitizedQueueName}
), TIMEOUT {options.ReceiveTimeout.TotalMilliseconds};";
}
public void Start(TriggerListenerOptions options, CancellationToken cancellationToken = default(CancellationToken))
{
if (_running)
{
throw new InvalidOperationException("The message listener is already running.");
}
Log.Info($"Beginning listening on queue {options.QueueName}.");
_running = true;
InitializeSqlStatements(options);
_listenTask = Task.Run(async() => await Listen(options, cancellationToken).ConfigureAwait(false), cancellationToken);
}
protected async Task Listen(TriggerListenerOptions options, CancellationToken cancellationToken)
{
var currentIteration = 0L;
while (!_done)
{
try
{
if (cancellationToken.IsCancellationRequested)
{
cancellationToken.ThrowIfCancellationRequested();
}
currentIteration++;
Log.Debug($"Iteration {currentIteration}: Beginning.");
// Connect to the database
using (var connection = await GetOpenConnectionAsync(options).ConfigureAwait(false))
using (var transaction = connection.BeginTransaction(IsolationLevel.ReadCommitted))
{
Log.Debug($"Iteration {currentIteration}: Connection opened.");
// Read messages from the Service Broker queue
var messages = await ReceiveMessagesAsync(transaction, currentIteration).ConfigureAwait(false) ?? new List <TriggerMessage>();
try
{
// If the last message is an EndOfStream message, we need to end the conversation after
// processing all other messages.
var endOfStreamMessage = (messages.LastOrDefault()?.MessageType == END_OF_STREAM) ? messages.Last() : null;
if (endOfStreamMessage != null)
{
messages.RemoveAt(messages.Count - 1);
}
// Process the messages.
if (messages.Any())
{
Log.Debug($"Iteration {currentIteration}: Preparing to process {messages.Count} message(s).");
await ProcessMessagesAsync(messages).ConfigureAwait(false);
Log.Debug($"Iteration {currentIteration}: Successfully processed {messages.Count} message(s).");
}
// If all messages were processed successfully, commit the transaction to
// remove the messages from the queue.
await CommitAsync(transaction, currentIteration).ConfigureAwait(false);
if (endOfStreamMessage != null)
{
await EndConversationAsync(endOfStreamMessage.ConversationHandle, connection, currentIteration).ConfigureAwait(false);
}
}
catch (Exception ex)
{
Log.Error(
$"An error occurred while processing a message from queue {options.QueueName}. Potential data inconsistency if messages were processed. Rolling back RECEIVE action.",
ex);
// If there was an error processing any of the messages, roll back the transaction
// to return the messages to the queue.
await RollbackAsync(transaction, currentIteration).ConfigureAwait(false);
}
}
}
catch (Exception ex)
{
Log.Error("An error occurred while processing messages.", ex);
await Task.Delay(1000, cancellationToken).ConfigureAwait(false);
}
}
}
