public IDisposable Subscribe(long?lastProcessedCheckpoint,
Func <IReadOnlyList <Transaction>, SubscriptionInfo, Task> handler,
SubscriptionOptions options = null)
{
if (options == null)
{
options = new SubscriptionOptions();
}
if (handler == null)
{
throw new ArgumentNullException(nameof(handler));
}
return(createSubscription(lastProcessedCheckpoint, new Subscriber
{
HandleTransactions = async(transactions, info) => await HandleTransactions(transactions, handler, info).ConfigureAwait(false),
NoSuchCheckpoint = async info => await HandleUnknownCheckpoint(info, handler, options).ConfigureAwait(false)
}, options.Id));
}
private async Task HandleUnknownCheckpoint(SubscriptionInfo info, Func <IReadOnlyList <Transaction>, SubscriptionInfo, Task> handler, SubscriptionOptions options)
{
if (options.RestartWhenAhead)
{
await ExecuteWithPolicy(
info,
async() =>
{
await options.BeforeRestarting().ConfigureAwait(false);
Subscribe(null, handler, options);
},
abort : exception =>
{
LogProvider.GetLogger(typeof(Dispatcher)).FatalException(
"Failed to restart the projector.",
exception);
},
ignore : () => Subscribe(null, handler, options))
.ConfigureAwait(false);
// Dispose the subscription only after a new subscription is created
// to support CreateSubscription delegates which wait
// until the subscription detects being ahead
// and until all the existing transactions are processed by the new subscription
info.Subscription?.Dispose();
}
}
