Which tcm process executes which event system code

Question

In the implementation I'm working on there is a lot of event system (ES) code and there is an out-scaled publisher server. The publish/transport services are turned off on the CM server and all the ES code is deployed to both of them. Version of Tridion is 2013SP1.

My question is which services are required for running all the ES code? I'm especially interested in the following on the out-scaled publisher.

<PublishTransaction, SaveEventArgs>

The publisher and transport services are running, but what about the service host? Does it need to be running as well?

Some time ago I found some information about what service runs what code, but for the life of me I can't seem to dig it up once again. All I could find now are these two(three) articles but I couldn't really come to a conclusion to my dilemma.

Remote Debugging in Visual Studio Made Easy(ish)

Some are pretty straightforward, while others – I’m looking at you, event system – vary by what you’re implementing.
TridionServiceHost is used for debugging External Content Library (ECL) extensions, as well as publish events in the Event System.

Debugging a Tridion 2011 Event System

TcmServiceHost.exe fires the event that occurs when a Publish Transaction is created; TcmPublisher.exe fires publishing events based on Tridion.ContentManager.Extensibility.Events.PublishingEventArgs;

SDL docs

TcmServiceHost.exe You use this Windows Service process if you connect to the Core Service through net.tcp. This includes the use of Content Manager Explorer and Experience Manager.
TcmPublisher.exe Any functionality related to publishing uses this process. That is, to debug any Event Handler code that is triggered by an action related to publishing, as well as any template code executed during publishing, attach to TcmPublisher.exe

Besides that specific one, an "overview" of the: "item types/args <=> service" would also be useful.

Thank you.

Answer 1

In general, the TOM.NET Event System is an in-process system; the event handlers are loaded and executed in the process which hosts the CM Kernel (more specifically: the process which hosts the CM Kernel action that triggers the event).

Specifically, the PublishTransaction Save action is typically performed by the Publisher Service (which acts as a CM Kernel host for all publishing-related actions that happen after the publishing queue). However, it is theoretically also possible to Save a PublishTransaction through the Core Service, in which case the event would be handled in the Core Service Host (either TcmServiceHost.exe or w3wp.exe, depending on which Core Service endpoint was used).

On the other hand, the Publish action itself (which enqueues a PublishTransaction) is typically performed by the Core Service (triggered by CME, custom Core Service client code or some event handler which runs in the Core Service), but it could also be performed by the Publisher Service (triggered by template code or some event handler which runs in the Publisher Service).

I'm sorry, I can't make it any easier. :-)