Feature summary (what you would like to be able to do and where):

It remains challenging to remove ResourceLoader modules without disrupting communities relying on them. ResourceLoader supports a "deprecated" keyword that prints a message to the console. However there is no way to look up impact across all our wikis. Having this information in logstash - e.g. number of page views using a certain module would make life a lot easier.

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):
When removing code, particularly code that is only being used by gadgets its hard to get a sense of whether users are relying on it. For example a gadget relying on jquery.ui may not actually work and may not be being used by anyone on the wiki. It would be useful to be able to create logstash dashboards that monitor usage of modules that are deprecated. For example - hypothetically of course! - if we identified the majority of page views came from 2 gadgets relying on jquery.ui we would be able to work with those communities to upgrade those gadgets and then remove the code.

I know we've done similar things in the past for legacy configuration variables.

Benefits (why should this be implemented?):

• This will give us more confidence that users are not impacted when we remove code.
• This will allow us to identify gadgets that are high priority to migrate away from
• We can base code removals on page views rather than "number of gadgets"