arbiter-hasql (hasql)

hasql and resource-pool. Handlers receive a Hasql.Connection in the worker transaction.

import Pqi.Ffi qualified as Ffi

env <- ArbH.createHasqlEnv (Proxy @AppRegistry) (ArbH.toHasqlConnect Ffi.adapter connStr) "arbiter"
ArbH.runHasqlDb env $ Arb.insertJob (Arb.defaultJob $ SendWelcome "alice@example.com" "Alice")

toHasqlConnect takes the transport adapter and the connection string. pqi-ffi wraps libpq. pqi-native is pure Haskell.

For hasql 1.x, turn off the hasql2 flag in cabal.project. Then toHasqlConnect takes only the connection string:

package arbiter-hasql
  flags: -hasql2

Share a transaction with external hasql work:

-- Session.script (hasql >= 1.10) or Session.sql (hasql < 1.10)
_ <- Hasql.use conn (Session.script "BEGIN")
ArbH.inTransaction @AppRegistry conn "arbiter" $
  Arb.insertJob (Arb.defaultJob (ProcessOrder orderId))
_ <- Hasql.use conn (Session.script "COMMIT")

With a custom pool, the environment reserves one connection for LISTEN/NOTIFY. Any adapter can open the pool:

import Data.Pool (defaultPoolConfig, newPool)
import Pqi.Ffi qualified as Ffi

let acquire = Hasql.acquire Ffi.adapter (ArbH.hasqlSettings connStr) >>= either (fail . show) pure
pool <- newPool (defaultPoolConfig acquire Hasql.release 60 10)
env <- ArbH.createHasqlEnvWithPool (Proxy @AppRegistry) pool "arbiter"

Environment and pool constructors: arbiter-hasql Haddocks.