backgrounDRb versus DRb...

Actually, ActiveRecord is thread safe. Set
ActiveRecord::Base.allow_concurrency to true in your Backgroun/DRb

Actually if you set allow_concurreny to true then you must *always* remember to call ActiveRecord::Base.verify_active_connections! at the end of each worker. Otherwise AR in multi threaded mode uses a database connection *per thread* and never releases them unless you call verify_active_connections! . If you don't release the connections then you will rapidly use all the database handles your database will allow.

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