PublishTransaction save event triggered multiple times

Question

I have a custom event system handler that sends an email when a publish transaction fails. The event is registered like this:

this.EventSystem.Subscribe<PublishTransaction, SaveEventArgs>    
    (this.SendNotificationEmail, EventPhases.TransactionCommitted);

The SendNotificationEmail method looks like this:

private void SendNotificationEmail(PublishTransaction transaction, 
    SaveEventArgs args, EventPhases phases)
{
    if (transaction.Instruction.ResolveInstruction.Purpose == ResolvePurpose.Publish && 
        transaction.State == PublishTransactionState.Failed)
    {
        // Send email
    }        
}

The issue I'm having is that the SendNotificationEmail method is called twice per publication transaction. This leads to multiple emails per failed transaction.

Any ideas why the event would be triggered more than once?

Answer 1

In general, the Save event is called for any save (change) of the PublishTransaction, not only for state changes. I'm not sure why a second save happens when the state is Failed (perhaps additional info is received from CD transport/deployment).

Anyways, your implementatiom should not rely on a single Save event, but detect the state change. You could do that by hooking into the Initiated phase of the save and, if the state is Failed, load another instance of the PublishTransaction to test if the state before the save event occurred was already Failed or not.

Answer 2

While publishing an item, each publishing target results in a transaction. In your code you are subscribing SendNotificationEmail method per transaction.

So If you publish to a multiple publishing targets, the "SendNotificationEmail" method will be called for each target(or transaction) and if it fails, the email will be send per target(or transaction) and will result in multiple emails.