All the Things I Thought I Couldn't Do
summary
Implements granular connection swapping for Active Record by moving role tracking into a shard→pool_config map and adding a pool manager, plus a public API like connected_to_many to swap multiple connections without nested blocks. Ships to production at GitHub (15 databases), reduces unnecessary primary queries, and lands in rails 6.1 as opt‑in via legacy_connection_handling. Shows concrete bugs found (prevent_writes and multiple abstract classes), fixes made, and that the feature actually works under real load.
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chapters (10)
- 0:00Start
- 28:54Why a Rails Application Might Need Multiple Databases
- 30:27Automatic Switcher
- 31:51Manual Switching
- 32:27Brief History of Connection Management
- 39:46Nesting Calls
- 54:04Why We Think Our Pairing Is Successful
- 1:03:05Learn a Foreign Language
- 1:03:54Measure Progress
- 1:05:16Measuring Progress
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