Trigger Workflow when specific files are written to Cloud Storage?

[nick-youngblut]

Task: trigger a GCP workflow when a specific file (e.g., "this_file.txt") is added to a Cloud Storage bucket.

Challenge: It appears that Eventarc triggers for Workflows do now allow filtering of events to specific files in specific buckets (although this can be done for triggering Cloud Run by setting the trigger on audit logs). 100's of 1000's of files are added to the target bucket, so I MUST have filtering of events to just specifically named files; otherwise, the GCP workflow would be triggered 100's of 1000's of times. 

Question1: Why isn't file name filtering directly available for Eventarc triggering of GCP Workflows? 

Question2: Can I use Pub/Sub to filter the Eventarc triggers (in my case 100's of 1000's of events for each file added to the bucket) to just the target files: Eventarc => Pub/Sub => Workflow?