Coordinator

trait Coordinator[F[_], TID, BID, Q, R] 
  def create(
      id: TID,
      query: Q,
      branch: BID,
      otherBranches: BID*
  ): Resource[F, Transaction[F, BID, Q, R]]

Coordinator allows for creating and recovering transactions of a certain type. Internally, it implements the two-phase commit protocol to guarantee a final transaction state of either committed or aborted.

The create method creates a new transaction with the given id, query and branches, and returns a Transaction handle.

Parameters of create are:

  • id: the transaction identifier
  • query: the payload sent to branches
  • branch...: identifiers for the branches involved in the transaction
Compatibility

Behavior for each branch is defined by the branchForID function passed to the Coordinator upon creation. This is invoked upon node restart for any pending transaction. It is therefore important to consider compatibility aspects if any change is done on this behavior.

The transaction might be in a partial preparation readiness state, and rollout of the new version will pick up preparation where it left off. As long as the new behavior is compatible with the old, this is not a problem.

Resource

The asResource convenience implicit def will wrap the transaction instance into a Resource, with release leading to transaction abort if it is still pending (or a no-op if the transaction is already completed).

0.4.0