DistributedTransactions.Terminology.md

Distributed Transactions Library Terminology

Operation - an atomic action that can finish successfully (expected) or unsuccessfully.

• Because of library is about distributed functionality, operation is an action that is aimed to add\update\delete data at another microservice.
• Operation interface is easy to understand - it encapsulates a commit and rollback methods.

Task CommitAsync(CancellationToken cancellationToken);

Task RollbackAsync(CancellationToken cancellationToken);

• Operation can exist in three states:

public enum OperationStatus
{
    Committed,
    NeedsToRollback,
    FailedToRollback
    Rollbacked
}

Transaction - a set of operations. They are grouped by the same transaction_type. Transaction can exist in these states:

public enum TransactionStatus
{
    // successful flow
    Created,
    FinishedCorrectly,

    // finally successful flow
    FinishedWithRollback,

    // unsuccessful flow
    NeedsToRollback,
    FailedToRollback
    Failed
}

• Created stands for a created transaction, but no operations were executed so far.
• FinishedCorrectly means that transaction has executed all of operations successfully.
• NeedsToRollback transaction stands for a transaction, to which some operations are bound, which are in the same state. So we definitely can try to query OperationEntity[] from a database and try to rollback them.
• FailedToRollback transaction means it was in NeedsToRollback state, but failed to rollback. You need to be cautious maybe you have to manually rollback such operations because they can infinitely try to rollback and never ever succeed.
• FinishedWithRollback means transaction has failed before N times, but finally at some moment it succeeded to rollback data
• Failed means it was created, but the first operation has failed, so we could not rollback it, because no data needs to be rollback-ed. However there is no reason to leave transaction in Created state, because we know it has failed.