EventLogging currently doesn't allow flagging specific events (or events originating from a specific client/IP address/IP range) as "test events". As a result, the production logs are filled with spurious events originating from hosts such as "localhost", "MyWiki.local" etc.
This is problematic because data consumers often query/count events unaware that they need to filter out these events. Whitelisting production hosts on the data consumer end is not a practical option. Engineers are resorting to hacks like [1] to address this problem, but a test flag doesn't belong in a data model. Instead, we need to support a test mode that the client can enable which will flag any incoming event as test. If the event passes validation, it should be stored in a different log (it could be a <schema_name>_<schema_revid>_test table or a table in a separate db) to allow data QA and troubleshooting.
[1] see "testing" field in https://meta.wikimedia.org/wiki/Schema:MobileWebWikiGrokResponse
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