/// <summary>
/// The algorithm stores metadata about messages that are going to be sent before the claim check entries are stored
/// in order to prevent accumulation of garbage messages in the claim check. First, the IDs of messages that are about
/// to be sent are stored in the transaction record with assigned attempt ID and incoming message ID. Then, the message
/// bodies are actually uploaded to the claim check. Next, the transaction record is committed.
///
/// At any point in time the OutgoingMessages collection of the transaction record may contain messages produced by
/// processing different incoming messages and different attempts but they don't interfere with each other e.g.
/// - Message A processing attempt 1 is started, resulting in message records stored as A-1-1 and A-1-2. Then it fails.
/// - Message B processing attempt 1 is started, resulting in B-1-1 and B-1-2
/// - Message B processing attempt 1 is finished. No claim check message are removed.
/// - Message A processing attempt 2 is started, resulting in message records stored as A-2-1.
/// - Message A processing attempt 2 is finished. Messages A-1-1 and A-1-2 are deleted.
/// </summary>
public async Task <ProcessingResult <TResult> > Process <TResult>(string currentMessageId, ITransactionRecordContainer transaction, TContext context,
Func <TContext, ITransactionContext, Task <ProcessingResult <TResult> > > invokeMessageHandlers)
{
await transaction.Load().ConfigureAwait(false);
var previousTransactionId = transaction.MessageId;
if (previousTransactionId != null)
{
log.Log($"Unfinished transaction {previousTransactionId} detected. Attempting to complete that transaction.");
await FinishProcessing(transaction).ConfigureAwait(false);
if (previousTransactionId == currentMessageId)
{
log.Log($"Duplicate message {currentMessageId} detected. Ignoring.");
return(ProcessingResult <TResult> .Duplicate);
}
}
var attemptId = Guid.NewGuid();
log.Log($"Beginning attempt {attemptId} to process message {currentMessageId}.");
await transaction.BeginStateTransition().ConfigureAwait(false);
var result = await invokeMessageHandlers(context, new TransactionContext(attemptId, transaction)).ConfigureAwait(false);
if (result.IsDuplicate)
{
log.Log($"Duplicate message {currentMessageId} detected. Ignoring.");
return(result);
}
log.Log($"Committing transaction for attempt {attemptId} message {currentMessageId}.");
await transaction.CommitStateTransition(currentMessageId, attemptId).ConfigureAwait(false);
await FinishProcessing(transaction).ConfigureAwait(false);
return(result);
}
public Task BeginStateTransition()
{
return(impl.BeginStateTransition());
}