version

type Check ¶

type Check interface {
	// contains filtered or unexported methods
}

Check defines the contract for an optimistic concurrency version check. Implementations of this interface are passed to the `AppendEvents` method of an event log to ensure that the state of the aggregate has not changed since it was last read.

type CheckExact ¶

type CheckExact Version

CheckExact is an implementation of the Check interface that requires the aggregate's current version in the event log to exactly match the expected version. This is the most common strategy for optimistic concurrency.

Usage:

// Expects the aggregate to be at version 5 before appending new events.
expected := version.CheckExact(5)
store.AppendEvents(ctx, id, expected, rawEvents)

func (expected CheckExact) CheckExact(actualVersion Version) error

type ConflictError ¶

type ConflictError struct {
	Expected Version
	Actual   Version
}

ConflictError is the error returned when an attempt to save an aggregate fails due to an optimistic concurrency violation. This means that another process has modified the aggregate between the read and write operations.

The 'Expected' field holds the version the application thought the aggregate was at, and 'Actual' holds the version that was found in the event log. This information is useful for handling the conflict, for example by retrying the operation.

func NewConflictError(expected Version, actual Version) *ConflictError

func (err ConflictError) Error() string

type Selector ¶

type Selector struct {
	From Version `exhaustruct:"optional"`
	To   Version `exhaustruct:"optional"`
}

Selector specifies a range of events to retrieve from the event log.

Usage:

// Get events from version 11 onwards
selector := version.Selector{From: 11}
repo.GetVersion(ctx, myID, selector)

// Get events up to version 25
selector := version.Selector{To: 25}
repo.GetVersion(ctx, myID, selector)

// Get events from version 11 to version 25. ⚠️ Only use this if you know what you're doing.
selector := version.Selector{From: 11, To: 25}
repo.GetVersion(ctx, myID, selector)

func SelectExact(to Version) Selector

func SelectFrom(from Version) Selector

func SelectInterval(from Version, to Version) Selector

type Version ¶

type Version uint64

Version represents the sequential number of an event within an aggregate's stream, or the state of an aggregate after a sequence of events has been applied. It is the base of optimistic concurrency control in the framework. An aggregate with no events has version 0. The first event applied results in version 1.

var Zero Version = 0