I would like to discuss some additional measures that can be added on top of this support. Once we reach consensus, I'll file a JIRA for 0.8. Note that these apply to the exchange bus and not to component code.
1. Errors on In-Only MEPs should always be logged at WARNING. After the change Lukasz made, these are logged at DEBUG (like all errors/faults) today. I think the case or errors on In-Only is unique because no handler is invoked to deal with the error. From a user standpoint, this is effectively the same as the error getting dropped. I don't think users will want to bump the logging to DEBUG to get notified of these situations. Faults/errors on In-Out MEPs can follow the current pattern of logging at DEBUG.
2. I would like to see a pretty debug message which includes some context on the invocation in addition to the stack trace. Maybe the service name, reference name, operation, etc. That would be the "header" of the log message and the detail would be the actual fault content or exception.
3. This might be possible with what's already in 1245, but can the logger logic be replaced/augmented by a user handler? I'm thinking of a scenario where a user might deploy a specific logger or something with their app to report errors.