Reverse Engineering

Herein lie things we have learned that were not obvious about the event log.

Retired entities are null

The entity field is null for retired entities, as determined when you read the log, not when the log was created. Ergo, if you are processing a backlog of log events, you can find yourself dealing with “Change” or even “New” events with a null entity field.

It is still possible to read the entity via a $FROM filter:

>>> sg.find_one('Task', [('$FROM$EventLogEntry.entity.id', 'is', 2017315)], [], retired_only=True)
{'type': 'Task', 'id': 67519}

This is exposed via Event.find_retired_entity().

Multi-Entity changes have no new_value

Changes to a multi_entity do not have a new_value and/or old_value in the meta. Instead, there is a list of entities added and removed in added and removed (respectively) in meta.

Back-references invade metadata

The meta field is a mixture of referee and referrer data when it is the backref of a multi_entity field.

E.g. if you set the the Task.entity to be a Shot, Shot.tasks will be updated to include that Task. The event pertaining to Shot.tasks will contain a few oddities which match the Task:

• entity_type
• entity_id
• field_data_type

If you combine this with the retired entity rule, you see that you can’t even derive what the referenced entity was. There are two backup plans:

1. You can lookup the other log entry via original_event_log_entry_id to figure out what the entity was set to.
2. Use the entity type formatted into the event type, and the $FROM$ syntax to select the entity with retired_only=True.

"Reading" meta-type

The type field is of the format {domain}_{entity_type}_{subtype}, in which domain is the string "Shotgun" for anything triggered by Shotgun, entity_type is the type of the entity that the event’s action was upon, and subtype is the action itself, e.g. "New", "Change", etc..

We have seen at least one “meta” entity_type in which it does not match the actual type of the entity field: "Reading".

"Reading" appears to be a meta-type which is describing when a human has read a note attached to an entity:

{
    "attribute_name": "read_by_current_user",
    "entity": {
        "id": 9174,
        "name": "<note goes here>",
        "type": "Note"
    },
    "event_type": "Shotgun_Reading_Change",
    "id": 2020717,
    "meta": {
        "attribute_name": "read_by_current_user",
        "new_value": "read",
        "old_value": null,
        "type": "attribute_change"
    },
    "type": "EventLogEntry",
    "user": {
        "id": 78,
        "name": "<name of human>",
        "type": "HumanUser"
    }
}