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ea0278cf27
This patch adds a timed LRU cache implementation and a compute node info cache on top of that. Cache entries might expire on their own (default ttl=5mins) or become invalid due to real-world events, e.g. compute node scale-to-zero event, so we add a connection retry loop with a wake-up call. Solved problems: - [x] Find a decent LRU implementation. - [x] Implement timed LRU on top of that. - [x] Cache results of `proxy_wake_compute` API call. - [x] Don't invalidate newer cache entries for the same key. - [x] Add cmdline configuration knobs (requires some refactoring). - [x] Add failed connection estab metric. - [x] Refactor auth backends to make things simpler (retries, cache placement, etc). - [x] Address review comments (add code comments + cleanup). - [x] Retry `/proxy_wake_compute` if we couldn't connect to a compute (e.g. stalled cache entry). - [x] Add high-level description for `TimedLru`. TODOs (will be addressed later): - [ ] Add cache metrics (hit, spurious hit, miss). - [ ] Synchronize http requests across concurrent per-client tasks (https://github.com/neondatabase/neon/pull/3331#issuecomment-1399216069). - [ ] Cache results of `proxy_get_role_secret` API call.