eventhorizon

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Published: Oct 12, 2021 License: Apache-2.0 Imports: 9 Imported by: 273

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Event Horizon

Event Horizon is a CQRS/ES toolkit for Go.

NOTE: Event Horizon is used in production systems but the API is not final!

CQRS stands for Command Query Responsibility Segregation and is a technique where object access (the Query part) and modification (the Command part) are separated from each other. This helps in designing complex data models where the actions can be totally independent from the data output.

ES stands for Event Sourcing and is a technique where all events that have happened in a system are recorded, and all future actions are based on the events instead of a single data model. The main benefit of adding Event Sourcing is traceability of changes which can be used for example in audit logging. Additionally, "incorrect" events that happened in the past (for example due to a bug) can be compensated for with an event which will make the current data "correct", as that is based on the events.

Read more about CQRS/ES from one of the major authors/contributors on the subject: http://codebetter.com/gregyoung/2010/02/16/cqrs-task-based-uis-event-sourcing-agh/

Other material on CQRS/ES:

Inspired by the following libraries/examples:

Suggestions are welcome!

Usage

See the example folder for a few examples to get you started.

Get Involved

Event Store Implementations

Official
  • Memory - Useful for testing and experimentation.
  • MongoDB - One document per aggregate with events as an array. Beware of the 16MB document size limit that can affect large aggregates.
  • MongoDB v2 - One document per event with an additional document per aggregate. This event store is also capable of keeping track of the global event position, in addition to the aggregate version.
  • Recorder - An event recorder (middleware) that can be used in tests to capture some events.
  • Tracing - Adds distributed tracing support to event store operations with OpenTracing.
Contributions / 3rd party

Event Bus Implementations

Official
  • GCP Cloud Pub/Sub - Using one topic with multiple subscribers.
  • NATS - Using Jetstream features.
  • Kafka - Using one topic with multiple consumer groups.
  • Local - Useful for testing and experimentation.
  • Redis - Using Redis streams.
  • Tracing - Adds distributed tracing support to event publishing and handling with OpenTracing.
Contributions / 3rd party

Repo Implementations

Official
  • Memory - Useful for testing and experimentation.
  • MongoDB - One document per projected entity.
  • Version - Adds support for reading a specific version of an entity from an underlying repo.
  • Cache - Adds support for in-memory caching of entities from an underlying repo.
  • Tracing - Adds distributed tracing support to an repo operations with OpenTracing.

Development

To develop Event Horizon you need to have Docker and Docker Compose installed.

To run all unit tests:

make test

To run and stop services for integration tests:

make run
make stop

To run all integration tests:

make test_integration

Testing can also be done in docker:

make test_docker
make test_integration_docker

License

Event Horizon is licensed under Apache License 2.0

http://www.apache.org/licenses/LICENSE-2.0

Documentation

Overview

Package eventhorizon is a CQRS/ES toolkit for Go.

Index

Constants

View Source
const DefaultMinVersionDeadline = 10 * time.Second

DefaultMinVersionDeadline is the deadline to use when creating a min version context that waits.

Variables

View Source
var (
	// ErrAggregateNotFound is when no aggregate can be found.
	ErrAggregateNotFound = errors.New("aggregate not found")
	// ErrAggregateNotRegistered is when no aggregate factory was registered.
	ErrAggregateNotRegistered = errors.New("aggregate not registered")
)
View Source
var (
	// ErrNoEventsToAppend is when no events are available to append.
	ErrNoEventsToAppend = errors.New("no events to append")
	// ErrInvalidEvent is when an event does not implement the Event interface.
	ErrInvalidEvent = errors.New("invalid event")
	// ErrIncorrectEventVersion is when an event is for an other version of the aggregate.
	ErrIncorrectEventVersion = errors.New("mismatching event version")
	// ErrCouldNotSaveEvents is when events could not be saved.
	ErrCouldNotSaveEvents = errors.New("could not save events")
)
View Source
var (
	// ErrEntityNotFound is when a entity could not be found.
	ErrEntityNotFound = errors.New("could not find entity")
	// ErrCouldNotLoadEntity is when a entity could not be loaded.
	ErrCouldNotLoadEntity = errors.New("could not load entity")
	// ErrCouldNotSaveEntity is when a entity could not be saved.
	ErrCouldNotSaveEntity = errors.New("could not save entity")
	// ErrCouldNotRemoveEntity is when a entity could not be removed.
	ErrCouldNotRemoveEntity = errors.New("could not remove entity")
	// ErrMissingEntityID is when a entity has no ID.
	ErrMissingEntityID = errors.New("missing entity ID")
	// ErrEntityHasNoVersion is when an entity has no version number.
	ErrEntityHasNoVersion = errors.New("entity has no version")
	// ErrIncorrectEntityVersion is when an entity has an incorrect version.
	ErrIncorrectEntityVersion = errors.New("incorrect entity version")
)
View Source
var ErrCommandNotRegistered = errors.New("command not registered")

ErrCommandNotRegistered is when no command factory was registered.

View Source
var ErrEventDataNotRegistered = errors.New("event data not registered")

ErrEventDataNotRegistered is when no event data factory was registered.

View Source
var ErrHandlerAlreadyAdded = errors.New("handler already added")

ErrHandlerAlreadyAdded is returned when calling AddHandler weth the same handler twice.

View Source
var ErrMissingHandler = errors.New("missing handler")

ErrMissingHandler is returned when calling AddHandler with a nil handler.

View Source
var ErrMissingMatcher = errors.New("missing matcher")

ErrMissingMatcher is returned when calling AddHandler without a matcher.

Functions

func AggregateIDFromContext added in v0.9.0

func AggregateIDFromContext(ctx context.Context) (uuid.UUID, bool)

AggregateIDFromContext return the command type from the context.

func CheckCommand

func CheckCommand(cmd Command) error

CheckCommand checks a command for errors.

func CompareEventSlices added in v0.11.0

func CompareEventSlices(evts1, evts2 []Event, opts ...CompareOption) bool

CompareEventSlices compares two slices of events, using options.

func CompareEvents added in v0.11.0

func CompareEvents(e1, e2 Event, options ...CompareOption) error

CompareEvents compares two events, with options for ignoring timestamp, version etc.

func MarshalContext

func MarshalContext(ctx context.Context) map[string]interface{}

MarshalContext marshals a context into a map.

func NewContextWithAggregateID added in v0.9.0

func NewContextWithAggregateID(ctx context.Context, aggregateID uuid.UUID) context.Context

NewContextWithAggregateID adds a aggregate ID on the context.

func NewContextWithAggregateType added in v0.9.0

func NewContextWithAggregateType(ctx context.Context, aggregateType AggregateType) context.Context

NewContextWithAggregateType adds a aggregate type on the context.

func NewContextWithCommandType added in v0.9.0

func NewContextWithCommandType(ctx context.Context, commandType CommandType) context.Context

NewContextWithCommandType adds a command type on the context.

func RegisterAggregate

func RegisterAggregate(factory func(uuid.UUID) Aggregate)

RegisterAggregate registers an aggregate factory for a type. The factory is used to create concrete aggregate types when loading from the database.

An example would be:

RegisterAggregate(func(id UUID) Aggregate { return &MyAggregate{id} })

func RegisterCommand

func RegisterCommand(factory func() Command)

RegisterCommand registers an command factory for a type. The factory is used to create concrete command types.

An example would be:

RegisterCommand(func() Command { return &MyCommand{} })

func RegisterContextMarshaler

func RegisterContextMarshaler(f ContextMarshalFunc)

RegisterContextMarshaler registers a marshaler function used by MarshalContext.

func RegisterContextUnmarshaler

func RegisterContextUnmarshaler(f ContextUnmarshalFunc)

RegisterContextUnmarshaler registers a marshaler function used by UnmarshalContext.

func RegisterEventData

func RegisterEventData(eventType EventType, factory func() EventData)

RegisterEventData registers an event data factory for a type. The factory is used to create concrete event data structs when loading from the database.

An example would be:

RegisterEventData(MyEventType, func() Event { return &MyEventData{} })

func UnmarshalContext

func UnmarshalContext(ctx context.Context, vals map[string]interface{}) context.Context

UnmarshalContext unmarshals a context from a map.

func UnregisterCommand

func UnregisterCommand(commandType CommandType)

UnregisterCommand removes the registration of the command factory for a type. This is mainly useful in mainenance situations where the command type needs to be switched at runtime.

func UnregisterEventData

func UnregisterEventData(eventType EventType)

UnregisterEventData removes the registration of the event data factory for a type. This is mainly useful in mainenance situations where the event data needs to be switched in a migrations.

Types

type Aggregate

type Aggregate interface {
	// Entity provides the ID of the aggregate.
	Entity

	// AggregateType returns the type name of the aggregate.
	// AggregateType() string
	AggregateType() AggregateType

	// CommandHandler is used to handle commands.
	CommandHandler
}

Aggregate is an interface representing a versioned data entity created from events. It receives commands and generates events that are stored.

The aggregate is created/loaded and saved by the Repository inside the Dispatcher. A domain specific aggregate can either implement the full interface, or more commonly embed *AggregateBase to take care of the common methods.

func CreateAggregate

func CreateAggregate(aggregateType AggregateType, id uuid.UUID) (Aggregate, error)

CreateAggregate creates an aggregate of a type with an ID using the factory registered with RegisterAggregate.

type AggregateError added in v0.9.0

type AggregateError struct {
	// Err is the error.
	Err error
}

AggregateError is an error caused in the aggregate when handling a command.

func (AggregateError) Cause added in v0.9.0

func (e AggregateError) Cause() error

Cause implements the github.com/pkg/errors Unwrap method.

func (AggregateError) Error added in v0.9.0

func (e AggregateError) Error() string

Error implements the Error method of the errors.Error interface.

func (AggregateError) Unwrap added in v0.9.0

func (e AggregateError) Unwrap() error

Unwrap implements the errors.Unwrap method.

type AggregateStore

type AggregateStore interface {
	// Load loads the most recent version of an aggregate with a type and id.
	Load(context.Context, AggregateType, uuid.UUID) (Aggregate, error)

	// Save saves the uncommitted events for an aggregate.
	Save(context.Context, Aggregate) error
}

AggregateStore is responsible for loading and saving aggregates.

type AggregateType

type AggregateType string

AggregateType is the type of an aggregate.

func AggregateTypeFromContext added in v0.9.0

func AggregateTypeFromContext(ctx context.Context) (AggregateType, bool)

AggregateTypeFromContext return the command type from the context.

func (AggregateType) String added in v0.8.0

func (at AggregateType) String() string

String returns the string representation of an aggregate type.

type Command

type Command interface {
	// AggregateID returns the ID of the aggregate that the command should be
	// handled by.
	AggregateID() uuid.UUID

	// AggregateType returns the type of the aggregate that the command can be
	// handled by.
	AggregateType() AggregateType

	// CommandType returns the type of the command.
	CommandType() CommandType
}

Command is a domain command that is sent to a Dispatcher.

A command name should 1) be in present tense and 2) contain the intent (MoveCustomer vs CorrectCustomerAddress).

The command should contain all the data needed when handling it as fields. These fields can take an optional "eh" tag, which adds properties. For now only "optional" is a valid tag: `eh:"optional"`.

func CreateCommand

func CreateCommand(commandType CommandType) (Command, error)

CreateCommand creates an command of a type with an ID using the factory registered with RegisterCommand.

type CommandFieldError

type CommandFieldError struct {
	Field string
}

CommandFieldError is returned by Dispatch when a field is incorrect.

func (CommandFieldError) Error

func (c CommandFieldError) Error() string

Error implements the Error method of the error interface.

type CommandHandler

type CommandHandler interface {
	HandleCommand(context.Context, Command) error
}

CommandHandler is an interface that all handlers of commands should implement.

func UseCommandHandlerMiddleware

func UseCommandHandlerMiddleware(h CommandHandler, middleware ...CommandHandlerMiddleware) CommandHandler

UseCommandHandlerMiddleware wraps a CommandHandler in one or more middleware.

type CommandHandlerFunc

type CommandHandlerFunc func(context.Context, Command) error

CommandHandlerFunc is a function that can be used as a command handler.

func (CommandHandlerFunc) HandleCommand

func (h CommandHandlerFunc) HandleCommand(ctx context.Context, cmd Command) error

HandleCommand implements the HandleCommand method of the CommandHandler.

type CommandHandlerMiddleware

type CommandHandlerMiddleware func(CommandHandler) CommandHandler

CommandHandlerMiddleware is a function that middlewares can implement to be able to chain.

type CommandIDer added in v0.9.0

type CommandIDer interface {
	// CommandID returns the ID of the command instance being handled.
	CommandID() uuid.UUID
}

CommandIDer provides a unique command ID to be used for request tracking etc.

type CommandType

type CommandType string

CommandType is the type of a command, used as its unique identifier.

func CommandTypeFromContext added in v0.9.0

func CommandTypeFromContext(ctx context.Context) (CommandType, bool)

CommandTypeFromContext return the command type from the context.

func (CommandType) String added in v0.8.0

func (ct CommandType) String() string

String returns the string representation of a command type.

type CompareConfig added in v0.11.0

type CompareConfig struct {
	// contains filtered or unexported fields
}

CompareConfig is a config for the ComparEvents function.

type CompareOption added in v0.11.0

type CompareOption func(*CompareConfig)

CompareOption is an option setter used to configure comparing of events.

func IgnorePositionMetadata added in v0.13.0

func IgnorePositionMetadata() CompareOption

IgnorePositionMetadata ignores the position in metadata when comparing events.

func IgnoreTimestamp added in v0.11.0

func IgnoreTimestamp() CompareOption

IgnoreTimestamp ignores the timestamps of events when comparing.

func IgnoreVersion added in v0.11.0

func IgnoreVersion() CompareOption

IgnoreVersion ignores the versions of events when comparing.

type ContextMarshalFunc

type ContextMarshalFunc func(context.Context, map[string]interface{})

ContextMarshalFunc is a function that marshalls any context values to a map, used for sending context on the wire.

type ContextUnmarshalFunc

type ContextUnmarshalFunc func(context.Context, map[string]interface{}) context.Context

ContextUnmarshalFunc is a function that marshalls any context values to a map, used for sending context on the wire.

type CouldNotHandleEventError added in v0.13.0

type CouldNotHandleEventError struct {
	// Err is the error.
	Err error
	// Event is the event that failed to be handled.
	Event Event
}

CouldNotHandleEventError is an error returned when an event could not be handled by an event handler.

func (CouldNotHandleEventError) Cause added in v0.13.0

func (e CouldNotHandleEventError) Cause() error

Cause implements the github.com/pkg/errors Unwrap method.

func (CouldNotHandleEventError) Error added in v0.13.0

func (e CouldNotHandleEventError) Error() string

Error implements the Error method of the errors.Error interface.

func (CouldNotHandleEventError) Unwrap added in v0.13.0

func (e CouldNotHandleEventError) Unwrap() error

Unwrap implements the errors.Unwrap method.

type Entity

type Entity interface {
	// EntityID returns the ID of the entity.
	EntityID() uuid.UUID
}

Entity is an item which is identified by an ID.

From http://cqrs.nu/Faq: "Entities or reference types are characterized by having an identity that's not tied to their attribute values. All attributes in an entity can change and it's still "the same" entity. Conversely, two entities might be equivalent in all their attributes, but will still be distinct."

type Event

type Event interface {
	// EventType returns the type of the event.
	EventType() EventType
	// The data attached to the event.
	Data() EventData
	// Timestamp of when the event was created.
	Timestamp() time.Time

	// AggregateType is the type of the aggregate that the event can be
	// applied to.
	AggregateType() AggregateType
	// AggregateID is the ID of the aggregate that the event belongs to.
	AggregateID() uuid.UUID
	// Version is the version of the aggregate after the event has been applied.
	Version() int

	// Metadata is app-specific metadata such as request ID, originating user etc.
	Metadata() map[string]interface{}

	// A string representation of the event.
	String() string
}

Event is a domain event describing a change that has happened to an aggregate.

An event struct and type name should:

1) Be in past tense (CustomerMoved)
2) Contain the intent (CustomerMoved vs CustomerAddressCorrected).

The event should contain all the data needed when applying/handling it.

func NewEvent

func NewEvent(eventType EventType, data EventData, timestamp time.Time, options ...EventOption) Event

NewEvent creates a new event with a type and data, setting its timestamp.

func NewEventForAggregate

func NewEventForAggregate(eventType EventType, data EventData, timestamp time.Time,
	aggregateType AggregateType, aggregateID uuid.UUID, version int, options ...EventOption) Event

NewEventForAggregate creates a new event with a type and data, setting its timestamp. It also sets the aggregate data on it. DEPRECATED, use NewEvent() with the WithAggregate() option instead.

type EventBus

type EventBus interface {
	EventHandler

	// AddHandler adds a handler for an event. Returns an error if either the
	// matcher or handler is nil, the handler is already added or there was some
	// other problem adding the handler (for networked handlers for example).
	AddHandler(context.Context, EventMatcher, EventHandler) error

	// Errors returns an error channel where async handling errors are sent.
	Errors() <-chan EventBusError

	// Close closes the EventBus and waits for all handlers to finish.
	Close() error
}

EventBus is an EventHandler that distributes published events to all matching handlers that are registered, but only one of each type will handle the event. Events are not garanteed to be handeled in order.

type EventBusError added in v0.5.0

type EventBusError struct {
	// Err is the error.
	Err error
	// Ctx is the context used when the error happened.
	Ctx context.Context
	// Event is the event handeled when the error happened.
	Event Event
}

EventBusError is an async error containing the error returned from a handler and the event that it happened on.

func (EventBusError) Cause added in v0.8.0

func (e EventBusError) Cause() error

Cause implements the github.com/pkg/errors Unwrap method.

func (EventBusError) Error added in v0.5.0

func (e EventBusError) Error() string

Error implements the Error method of the error interface.

func (EventBusError) Unwrap added in v0.9.0

func (e EventBusError) Unwrap() error

Unwrap implements the errors.Unwrap method.

type EventCodec added in v0.11.0

type EventCodec interface {
	// MarshalEvent marshals an event and the supported parts of context into bytes.
	MarshalEvent(context.Context, Event) ([]byte, error)
	// UnmarshalEvent unmarshals an event and supported parts of context from bytes.
	UnmarshalEvent(context.Context, []byte) (Event, context.Context, error)
}

EventCodec is a codec for marshaling and unmarshaling events to and from bytes.

type EventData

type EventData interface{}

EventData is any additional data for an event.

func CreateEventData

func CreateEventData(eventType EventType) (EventData, error)

CreateEventData creates an event data of a type using the factory registered with RegisterEventData.

type EventHandler

type EventHandler interface {
	// HandlerType is the type of the handler.
	HandlerType() EventHandlerType

	// HandleEvent handles an event.
	HandleEvent(context.Context, Event) error
}

EventHandler is a handler of events. If registered on a bus as a handler only one handler of the same type will receive each event. If registered on a bus as an observer all handlers of the same type will receive each event.

func UseEventHandlerMiddleware

func UseEventHandlerMiddleware(h EventHandler, middleware ...EventHandlerMiddleware) EventHandler

UseEventHandlerMiddleware wraps a EventHandler in one or more middleware.

type EventHandlerFunc

type EventHandlerFunc func(context.Context, Event) error

EventHandlerFunc is a function that can be used as a event handler.

func (EventHandlerFunc) HandleEvent

func (f EventHandlerFunc) HandleEvent(ctx context.Context, e Event) error

HandleEvent implements the HandleEvent method of the EventHandler.

func (EventHandlerFunc) HandlerType added in v0.4.0

func (f EventHandlerFunc) HandlerType() EventHandlerType

HandlerType implements the HandlerType method of the EventHandler by returning the name of the package and function: "github.com/looplab/eventhorizon.Function" becomes "eventhorizon-Function"

type EventHandlerMiddleware

type EventHandlerMiddleware func(EventHandler) EventHandler

EventHandlerMiddleware is a function that middlewares can implement to be able to chain.

type EventHandlerType added in v0.4.0

type EventHandlerType string

EventHandlerType is the type of an event handler, used as its unique identifier.

func (EventHandlerType) String added in v0.8.0

func (ht EventHandlerType) String() string

String returns the string representation of an event handler type.

type EventMatcher

type EventMatcher interface {
	// Match returns true if the matcher matches an event.
	Match(Event) bool
}

EventMatcher matches, for example on event types, aggregate types etc.

type EventOption added in v0.9.0

type EventOption func(Event)

EventOption is an option to use when creating events.

func ForAggregate added in v0.9.0

func ForAggregate(aggregateType AggregateType, aggregateID uuid.UUID, version int) EventOption

ForAggregate adds aggregate data when creating an event.

func FromCommand added in v0.9.0

func FromCommand(cmd Command) EventOption

FromCommand adds metadata for the originating command when crating an event. Currently it adds the command type and optionally a command ID (if the CommandIDer interface is implemented).

func WithGlobalPosition added in v0.13.0

func WithGlobalPosition(position int) EventOption

WithGlobalPosition sets the global event position in the metadata.

func WithMetadata added in v0.9.0

func WithMetadata(metadata map[string]interface{}) EventOption

WithMetadata adds metadata when creating an event. Note that the values types must be supported by the event marshalers in use.

type EventSource added in v0.7.0

type EventSource interface {
	// UncommittedEvents returns events that are not committed to the event store,
	// or handeled in other ways (depending on the caller).
	UncommittedEvents() []Event
	// ClearUncommittedEvents clears uncommitted events, used after they have been
	// committed to the event store or handled in other ways (depending on the caller).
	ClearUncommittedEvents()
}

EventSource is a source of events, used for getting events for handling, storing, publishing etc. Mostly used in the aggregate stores.

type EventStore

type EventStore interface {
	// Save appends all events in the event stream to the store.
	Save(ctx context.Context, events []Event, originalVersion int) error

	// Load loads all events for the aggregate id from the store.
	Load(context.Context, uuid.UUID) ([]Event, error)

	// Close closes the EventStore.
	Close() error
}

EventStore is an interface for an event sourcing event store.

type EventStoreError

type EventStoreError struct {
	// Err is the error.
	Err error
	// BaseErr is an optional underlying error, for example from the DB driver.
	BaseErr error
}

EventStoreError is an error in the event store.

func (EventStoreError) Cause added in v0.8.0

func (e EventStoreError) Cause() error

Cause implements the github.com/pkg/errors Unwrap method.

func (EventStoreError) Error

func (e EventStoreError) Error() string

Error implements the Error method of the errors.Error interface.

func (EventStoreError) Unwrap added in v0.9.0

func (e EventStoreError) Unwrap() error

Unwrap implements the errors.Unwrap method.

type EventStoreMaintenance added in v0.13.0

type EventStoreMaintenance interface {
	// Replace an event, the version must match. Useful for maintenance actions.
	// Returns ErrAggregateNotFound if there is no aggregate.
	Replace(context.Context, Event) error

	// RenameEvent renames all instances of the event type.
	RenameEvent(ctx context.Context, from, to EventType) error
}

EventStoreMaintenance is an interface with maintenance tools for an EventStore. NOTE: Should not be used in apps, useful for migration tools etc.

type EventType

type EventType string

EventType is the type of an event, used as its unique identifier.

func (EventType) String added in v0.8.0

func (et EventType) String() string

String returns the string representation of an event type.

type IsZeroer added in v0.14.4

type IsZeroer interface {
	IsZero() bool
}

IsZeroer is used to check if a type is zero-valued, and in that case is not allowed to be used in a command. See CheckCommand

type Iter

type Iter interface {
	Next(context.Context) bool
	Value() interface{}
	// Close must be called after the last Next() to retrieve error if any
	Close(context.Context) error
}

Iter is a stateful iterator object that when called Next() readies the next value that can be retrieved from Value(). Enables incremental object retrieval from repos that support it. You must call Close() on each Iter even when results were delivered without apparent error.

type MatchAggregates added in v0.8.0

type MatchAggregates []AggregateType

MatchAggregates matches any of the aggregate types, nil events never match.

func (MatchAggregates) Match added in v0.8.0

func (types MatchAggregates) Match(e Event) bool

Match implements the Match method of the EventMatcher interface.

type MatchAll added in v0.8.0

type MatchAll []EventMatcher

MatchAll matches all of the matchers.

func (MatchAll) Match added in v0.8.0

func (matchers MatchAll) Match(e Event) bool

Match implements the Match method of the EventMatcher interface.

type MatchAny

type MatchAny []EventMatcher

MatchAny matches any of the matchers.

func (MatchAny) Match added in v0.8.0

func (matchers MatchAny) Match(e Event) bool

Match implements the Match method of the EventMatcher interface.

type MatchEvents added in v0.8.0

type MatchEvents []EventType

MatchEvents matches any of the event types, nil events never match.

func (MatchEvents) Match added in v0.8.0

func (types MatchEvents) Match(e Event) bool

Match implements the Match method of the EventMatcher interface.

type ReadRepo

type ReadRepo interface {
	// InnerRepo returns the inner read repository, if there is one.
	// Useful for iterating a wrapped set of repositories to get a specific one.
	InnerRepo(context.Context) ReadRepo

	// Find returns an entity for an ID.
	Find(context.Context, uuid.UUID) (Entity, error)

	// FindAll returns all entities in the repository.
	FindAll(context.Context) ([]Entity, error)

	// Close closes the ReadRepo.
	Close() error
}

ReadRepo is a read repository for entities.

type ReadWriteRepo

type ReadWriteRepo interface {
	ReadRepo
	WriteRepo
}

ReadWriteRepo is a combined read and write repo, mainly useful for testing.

type RepoError

type RepoError struct {
	// Err is the error.
	Err error
	// BaseErr is an optional underlying error, for example from the DB driver.
	BaseErr error
}

RepoError is an error in the read repository.

func (RepoError) Cause added in v0.8.0

func (e RepoError) Cause() error

Cause implements the github.com/pkg/errors Unwrap method.

func (RepoError) Error

func (e RepoError) Error() string

Error implements the Error method of the errors.Error interface.

func (RepoError) Unwrap added in v0.9.0

func (e RepoError) Unwrap() error

Unwrap implements the errors.Unwrap method.

type Versionable

type Versionable interface {
	// AggregateVersion returns the version of the item.
	AggregateVersion() int
}

Versionable is an item that has a version number, used by version.ReadRepo.FindMinVersion().

type WriteRepo

type WriteRepo interface {
	// Save saves a entity in the storage.
	Save(context.Context, Entity) error

	// Remove removes a entity by ID from the storage.
	Remove(context.Context, uuid.UUID) error
}

WriteRepo is a write repository for entities.

Directories

Path Synopsis
aggregatestore
commandhandler
bus
gcp
eventhandler
examples
guestlist/memory
Package memory contains an example of a CQRS/ES app using memory as DB.
Package memory contains an example of a CQRS/ES app using memory as DB.
guestlist/mongodb
Package mongodb contains an example of a CQRS/ES app using the MongoDB adapter.
Package mongodb contains an example of a CQRS/ES app using the MongoDB adapter.
hack
middleware
Package UUID provides an easy to replace UUID package.
Package UUID provides an easy to replace UUID package.

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