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Susana Ferreira
6ef9670384
## Description This PR addresses database connection pool exhaustion during prebuilds reconciliation by introducing two changes: * `CanSkipReconciliation`: Filters out presets that don't need reconciliation before spawning goroutines. This ensures we only create goroutines for presets that will (_most likely_) perform database operations, avoiding unnecessary connection pool usage. * Dynamic `eg.SetLimit`: Limits concurrent goroutines based on the configured database connection pool size (`CODER_PG_CONN_MAX_OPEN / 2`). This replaces the previous hardcoded limit of 5, ensuring the reconciliation loop scales appropriately with the configured pool size while leaving capacity for other database operations. ## Changes * Add `CanSkipReconciliation()` method to `PresetSnapshot` that returns true for inactive presets with no running workspaces, no pending jobs, or expired prebuilds. * Add `maxDBConnections` parameter to `NewStoreReconciler` and compute `reconciliationConcurrency` as half the pool size (minimum 1). * Add `ReconciliationConcurrency()` getter method to `StoreReconciler`. * Add `eg.SetLimit(c.reconciliationConcurrency)` to bound concurrent reconciliation goroutines. * Add `PresetsTotal` and `PresetsReconciled` to `ReconcileStats` for observability. * Add `TestCanSkipReconciliation` unit tests. * Add `TestReconciliationConcurrency` unit tests. * Add benchmark tests for reconciliation performance. ## Benchmarks * `BenchmarkReconcileAll_NoOps`: Tests presets with no reconciliation actions. All presets are filtered by `CanSkipReconciliation`, resulting in no goroutines spawned and no database connections used. * `BenchmarkReconcileAll_ConnectionContention`: Tests presets where all require reconciliation actions. All presets spawn goroutines, but concurrency is limited by `eg.SetLimit(reconciliationConcurrency)`. * `BenchmarkReconcileAll_Mix`: Simulates a realistic scenario with a large subset of inactive presets (filtered by `CanSkipReconciliation`) and a smaller subset requiring reconciliation (limited by `eg.SetLimit`). Closes: https://github.com/coder/coder/issues/20606