Illustrates how to encapsulate a sequence of steps within a saga transaction and specify compensation steps for each.
In the sample, Task2 will throw an exception, then UndoTask2 and UndoTask1 will be triggered.
builder
.StartWith(context => Console.WriteLine("Begin"))
.Saga(saga => saga
.StartWith<Task1>()
.CompensateWith<UndoTask1>()
.Then<Task2>()
.CompensateWith<UndoTask2>()
.Then<Task3>()
.CompensateWith<UndoTask3>()
)
.OnError(Models.WorkflowErrorHandling.Retry, TimeSpan.FromSeconds(5))
.Then(context => Console.WriteLine("End"));This particular example will retry the saga every 5 seconds, but you could also simply fail completely, and process a master compensation task for the whole saga.
builder
.StartWith(context => Console.WriteLine("Begin"))
.Saga(saga => saga
.StartWith<Task1>()
.CompensateWith<UndoTask1>()
.Then<Task2>()
.CompensateWith<UndoTask2>()
.Then<Task3>()
.CompensateWith<UndoTask3>()
)
.CompensateWith<CleanUp>()
.Then(context => Console.WriteLine("End"));You could also only specify a master compensation step, as follows
builder
.StartWith(context => Console.WriteLine("Begin"))
.Saga(saga => saga
.StartWith<Task1>()
.Then<Task2>()
.Then<Task3>()
)
.CompensateWith<UndoEverything>()
.Then(context => Console.WriteLine("End"));Parameters can be passed to a compensation step as follows
builder
.StartWith<SayHello>()
.CompensateWith<PrintMessage>(compensate =>
{
compensate.Input(step => step.Message, data => "undoing...");
})A saga transaction can be expressed in JSON, by using the WorkflowCore.Primitives.Sequence step and setting the Saga parameter to true.
The compensation steps can be defined by specifying the CompensateWith parameter.
{
"Id": "Saga-Sample",
"Version": 1,
"DataType": "MyApp.MyDataClass, MyApp",
"Steps": [
{
"Id": "Hello",
"StepType": "MyApp.HelloWorld, MyApp",
"NextStepId": "MySaga"
},
{
"Id": "MySaga",
"StepType": "WorkflowCore.Primitives.Sequence, WorkflowCore",
"NextStepId": "Bye",
"Saga": true,
"Do": [
[
{
"Id": "do1",
"StepType": "MyApp.Task1, MyApp",
"NextStepId": "do2",
"CompensateWith": [
{
"Id": "undo1",
"StepType": "MyApp.UndoTask1, MyApp"
}
]
},
{
"Id": "do2",
"StepType": "MyApp.Task2, MyApp",
"CompensateWith": [
{
"Id": "undo2-1",
"NextStepId": "undo2-2",
"StepType": "MyApp.UndoTask2, MyApp"
},
{
"Id": "undo2-2",
"StepType": "MyApp.DoSomethingElse, MyApp"
}
]
}
]
]
},
{
"Id": "Bye",
"StepType": "MyApp.GoodbyeWorld, MyApp"
}
]
}