distributed-transactions

Two-Phase Commit: Order, Inventory, and Payment in Parallel

An order must reserve inventory and authorize payment atomically -- if payment fails after inventory is reserved, you have phantom stock. This workflow uses FORK_JOIN to prepare all three participants (order, inventory, payment) in parallel, then either commits all or rolls back all based on whether every participant voted "prepared."

Workflow

orderId, items, paymentMethod
              |
              v
    FORK_JOIN (prepare phase) --------+
    |              |                  |
    v              v                  v
+-----------------+ +-----------------+ +------------------+
| dtx_prepare_    | | dtx_prepare_    | | dtx_prepare_     |
| order           | | inventory       | | payment          |
+-----------------+ +-----------------+ +------------------+
  txId: OTX-...      txId: ITX-...       txId: PTX-...
  prepared: true     prepared: true      prepared: true
    |              |                  |
    +------ JOIN --+------------------+
              |
              v
     +-------------------+
     | dtx_commit_all    |   committed: true, globalTxId: GTX-...
     +-------------------+
         (or dtx_rollback_all if any prepare fails)

Workers

PrepareOrderWorker -- Prepares the order. Returns txId: "OTX-{timestamp}", prepared: true.

PrepareInventoryWorker -- Reserves inventory items. Returns txId: "ITX-{timestamp}", prepared: true.

PreparePaymentWorker -- Authorizes the payment method. Returns txId: "PTX-{timestamp}", prepared: true.

CommitAllWorker -- Commits all 3 transactions. Returns committed: true, globalTxId: "GTX-{timestamp}".

RollbackAllWorker -- Rolls back all transactions if any prepare failed. Returns rolledBack: true.

Tests

10 unit tests cover order/inventory/payment preparation, commit, and rollback.

Running

See ../../RUNNING.md for setup and execution instructions.