1.4 KiB
Simplex.Messaging.Agent.Store.Postgres
PostgreSQL backend — dual-pool connection management, schema lifecycle, and migration.
Source: Agent/Store/Postgres.hs
Dual pool architecture
connectPostgresStore creates two connection pools (dbPriorityPool and dbPool), each with poolSize connections. Priority pool is used by withTransactionPriority for operations that shouldn't be blocked by regular queries. Both pools are TBQueue-based — connections are taken and returned after use.
All connections are created eagerly at initialization, not lazily on demand.
uninterruptibleMask_ — pool atomicity invariant
See comment on connectStore. uninterruptibleMask_ prevents async exceptions from interrupting pool filling or draining. The invariant: when dbClosed = True, queues are empty; when False, queues are full (or connections are in-flight with threads that will return them). Interruption mid-fill would break this invariant.
Schema creation — fail-fast on missing
If the PostgreSQL schema doesn't exist and createSchema is False, the process logs an error and calls exitFailure. This prevents silent operation against the wrong schema.
execSQL — not implemented
execSQL throws "not implemented" — the PostgreSQL client doesn't support raw SQL execution via the agent API. The function exists only to satisfy the shared interface.