ctrlrun.postgres.PostgresStateStore — class, defined at src/ctrlrun/postgres.py:218
SQLiteStateStore does: psycopg connections are not
thread-safe, and the thread-local shape is the one close() is already specified against
(§2.7).
A connection outlives the thread that opened it, and that is a real limit worth stating.
A host running agents on a bounded, recycled thread pool is fine — the same threads keep
reusing the same connections. A host that starts a fresh thread per unit of work accumulates
one connection per thread that ever touched the store, and Postgres connections are far
scarcer than SQLite file handles: max_connections defaults to 100. close() releases every
one, so the mitigation is to close a store you are done with. The conformance suite met this
for real — ninety-six connections across twelve rounds of eight threads — and the failure
surfaced in a case that had nothing to do with it.
No pool ships. An operator may put pgbouncer in front in transaction mode, and it works
because this store holds nothing session-scoped: no advisory lock, no temp table, no prepared
statement it depends on surviving, no SET. That is the second reason §4.2.1 rejected
advisory locks, and it is a property worth keeping deliberately rather than by luck.