Writing a Backend

A backend is a MonadArbiter instance. Applications that use arbiter-orville must define this instance. Use the same interface to implement another adapter.

The class specifies a registry, handler type, and these database operations:

• RegistryOf specifies the queue registry for the monad.
• Handler specifies the handler type. It can include a connection argument if the database library supplies one.
• getSchema returns the Arbiter schema.
• executeQuery and executeStatement run a Query. The value contains its SQL text, parameters, and decoder.
• withDbTransaction starts a transaction or savepoint. A nested call must start a savepoint. This lets a finalization callback participate in the caller's transaction. See Worker Configuration.
• runHandlerWithConnection checks out a connection and runs a handler.
• getListener returns the shared LISTEN/NOTIFY listener. Return Nothing for polling mode. See Wakeups.

executeQueryPrepared is optional and uses executeQuery by default. Override it if the backend can prepare a statement one time for each connection and reuse the plan. The claim operation uses this method. See the performance data in Backend Integration.

See the MonadArbiter haddocks for each method's signature.