saga/saga_message.go

package saga

import (
	"fmt"
)

type SagaMessageType int

const (
	StartSaga SagaMessageType = iota
	EndSaga
	AbortSaga
	StartTask
	EndTask
	StartCompTask
	EndCompTask
)

func (s SagaMessageType) String() string {
	switch s {
	case StartSaga:
		return "Start Saga"
	case EndSaga:
		return "End Saga"
	case AbortSaga:
		return "Abort Saga"
	case StartTask:
		return "Start Task"
	case EndTask:
		return "End Task"
	case StartCompTask:
		return "Start Comp Task"
	case EndCompTask:
		return "End Comp Task"
	default:
		return "unknown"
	}
}

/*
 * Data Structure representation of a entry in the SagaLog.
 * Different SagaMessageTypes utilize different fields.
 * Factory Methods are supplied for creation of Saga Messages
 * and should be used instead of directly creatinga  sagaMessage struct
 */
type SagaMessage struct {
	SagaId  string
	MsgType SagaMessageType
	Data    []byte
	TaskId  string
}

func (s SagaMessage) String() string {
	return fmt.Sprintf("Message %s: Saga %s, Task %s", s.MsgType, s.SagaId, s.TaskId)
}

/*
 * StartSaga SagaMessageType
 *  - sagaId - id of the Saga
 *  - data - data needed to execute the saga
 */
func MakeStartSagaMessage(sagaId string, job []byte) SagaMessage {
	return SagaMessage{
		SagaId:  sagaId,
		MsgType: StartSaga,
		Data:    job,
	}
}

/*
 * EndSaga SagaMessageType
 *  - sagaId - id of the Saga
 */
func MakeEndSagaMessage(sagaId string) SagaMessage {
	return SagaMessage{
		SagaId:  sagaId,
		MsgType: EndSaga,
	}
}

/*
 * AbortSaga SagaMessageType
 *  - sagaId - id of the Saga
 */
func MakeAbortSagaMessage(sagaId string) SagaMessage {
	return SagaMessage{
		SagaId:  sagaId,
		MsgType: AbortSaga,
	}
}

/*
 * StartTask SagaMessageType
 *  - sagaId - id of the Saga
 *  - taskId - id of the started Task
 *  - data   - data that is persisted to the log, useful for
 *             diagnostic information
 */
func MakeStartTaskMessage(sagaId string, taskId string, data []byte) SagaMessage {
	return SagaMessage{
		SagaId:  sagaId,
		MsgType: StartTask,
		TaskId:  taskId,
		Data:    data,
	}
}

/*
 * EndTask SagaMessageType
 *  - sagaId - id of the Saga
 *  - taskId - id of the completed Task
 *  - data - any results from task completion
 */
func MakeEndTaskMessage(sagaId string, taskId string, results []byte) SagaMessage {
	return SagaMessage{
		SagaId:  sagaId,
		MsgType: EndTask,
		TaskId:  taskId,
		Data:    results,
	}
}

/*
 * StartCompTask SagaMessageType
 *  - sagaId - id of the Saga
 *  - taskId - id of the started compensating task.  Should
 *             be the same as the original taskId
 *  - data   - data that is persisted to the log, useful for
 *             diagnostic information
 */
func MakeStartCompTaskMessage(sagaId string, taskId string, data []byte) SagaMessage {
	return SagaMessage{
		SagaId:  sagaId,
		MsgType: StartCompTask,
		TaskId:  taskId,
		Data:    data,
	}
}

/*
 * EndCompTask SagaMessageType
 *  - sagaId - id of the Saga
 *  - taskId - id of the completed compensating task.  Should
 *             be the same as the original taskId
 *  - data - any results from compensating task completion
 */
func MakeEndCompTaskMessage(sagaId string, taskId string, results []byte) SagaMessage {
	return SagaMessage{
		SagaId:  sagaId,
		MsgType: EndCompTask,
		TaskId:  taskId,
		Data:    results,
	}
}