protected override async Task ExecuteAsync(CancellationToken cancellation)
{
while (!cancellation.IsCancellationRequested)
{
try // To make sure the background service keeps running
{
// When the queue is empty, this goes to sleep until an item is enqueued
var(sms, scheduledAt) = await _queue.DequeueAsync(cancellation);
// This SMS spent too long in the queue it is considered stale, SmsPollingJob will
// (and might have already) pick it up and send it again, so ignore it
if (IsStale(scheduledAt))
{
_logger.LogWarning($"Stale SMS remained in the {nameof(SmsQueue)} for {(DateTimeOffset.Now - scheduledAt).TotalSeconds} seconds. TenantId = {sms.TenantId}, MessageId = {sms.MessageId}.");
continue;
}
// Begin serializable transaction
using var trx = new TransactionScope(TransactionScopeOption.RequiresNew, new TransactionOptions { IsolationLevel = IsolationLevel.Serializable }, TransactionScopeAsyncFlowOption.Enabled);
// Update the state first (since this action can be rolled back)
await _repo.Notifications_SmsMessages__UpdateState(sms.TenantId, sms.MessageId, SmsState.Dispatched, DateTimeOffset.Now); // actions that modify state should not use cancellationToken
try
{
// Send the SMS after you update the state in the DB, since sending SMS
// is non-transactional and therefore cannot be rolled back
await _smsSender.SendAsync(sms);
}
catch (Exception ex)
{
_logger.LogWarning(ex, $"Failed to Dispatch SMS. TenantId = {sms.TenantId}, MessageId = {sms.MessageId}.");
// If sending the SMS fails, update the state to DispatchFailed together with the error message
await _repo.Notifications_SmsMessages__UpdateState(sms.TenantId, sms.MessageId, SmsState.DispatchFailed, DateTimeOffset.Now, ex.Message);
}
trx.Complete();
}
catch (Exception ex)
{
_logger.LogError(ex, $"Error in {nameof(SmsJob)}.");
}
}
}
public async Task HandleCallback(SmsEventNotification smsEvent, CancellationToken cancellation)
{
// Nothing to do
if (smsEvent == null || smsEvent.TenantId == null || smsEvent.TenantId == 0) // Right now we do not handle null tenant Ids, those were probably sent from identity or admin servers
{
return;
}
// Map the event to the database representation
var state = smsEvent.Event switch
{
SmsEvent.Sent => SmsState.Sent,
SmsEvent.Failed => SmsState.SendingFailed,
SmsEvent.Delivered => SmsState.Delivered,
SmsEvent.Undelivered => SmsState.DeliveryFailed,
_ => throw new InvalidOperationException($"[Bug] Unknown {nameof(SmsEvent)} = {smsEvent.Event}"), // Future proofing
};
// Update the state in the database (should we make it serializable?)
await _repo.Notifications_SmsMessages__UpdateState(smsEvent.TenantId.Value, smsEvent.MessageId, state, smsEvent.Timestamp, smsEvent.Error, cancellation);
}
