Committing multiple aggregates in a transaction

[theodorton]

Motivation

We would like to have consistency when aggregates with dependencies are saved to the database. In a case where two aggregates will be committed to in the same flow, it makes sense to be able to rollback both if one of them fails to commit due to a conflict.

New APIs

@ddes/core

• added AggregateRoot.build, which accepts the same arguments as AggregateRoot.commit and returns an AggregateCommit

@ddes/postgres

• added PostgresEventStore.commitInTransaction which will accept a list of AggregateCommits obtained through AggregateRoot.build

Example

const myStore = new PostgresEventStore({})

await retryOnVersionConflict(async () => {
  // Assume currentFooVersion and currentBarVersion is set

  const firstCommit = SomeAggregate.build('foo', currentFooVersion + 1, [{ type: 'SomeEvent' }])
  const secondCommit = OtherAggregate.build('bar', currentBarVersion + 1, [{ type: 'AnotherEvent' }])

  await myStore.commitInTransaction([
    firstCommit,
    secondCommit,
  ])
})

// vs the existing approach
await retryOnVersionConflict(async () => {
  // Assume currentFooVersion and currentBarVersion is set

  await SomeAggregate.commit('foo', currentFooVersion + 1, [{ type: 'SomeEvent' }])
  
  // If this next line fails, the commit above will not be rolled back in the database
  await OtherAggregate.commit('bar', currentBarVersion + 1, [{ type: 'AnotherEvent' }])
})

[krijoh92]

LGTM 👍

[krijoh92]

Nitpicky, but maybe call this insertCommit ?

[theodorton]

Addressed in d5ef9c4