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Add Exception Handling section for Parallel State (#244) 

* Add Exception Handling section for Parallel State

* fix section link

* updating roadmap
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Tihomir Surdilovic 2020-06-03 11:02:58 -04:00 committed by GitHub
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1
workflow/spec/roadmap.md
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@ -55,3 +55,4 @@ _Status description:_
| ✔️| Add examples comparing Brigade workflow and spec markups | [examples doc](examples-brigade.md) |
| ✔️| Update produceEvent data property | [spec doc](spec.md) |
| ✔️| Change uppercase property and enum types to lowercase | [spec doc](spec.md) |
| ✔️| Add Parallel State Exception Handling section | [spec doc](spec.md) |

174
workflow/spec/spec.md
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@ -1598,7 +1598,7 @@ The "completionType" enum specifies the different ways of completing branch exec
* n_of_m: State can transition once N number of branches have completed execution. In this case you should also
specify the "n" property to define this number.
Exceptions may occur during execution of branches of the Parallel state, this is described in detail in [this section](#parallel-state-exceptions).
#### <a name="parallel-state-branch"></a>Parallel State: Branch
@ -1671,6 +1671,178 @@ States within each branch are only allowed to transition to states defined in th
Transitions to other branches or workflow states are not allowed.
States outside a parallel state cannot transition to a states declared within branches.
#### <a name="parallel-state-exceptions"></a>Parallel State: Handling Exceptions
Exceptions that occur during execution of Parallel state branch execution.
By default exceptions that are not handled within states of branches stop branch execution and are propagated
to the Parallel state.
Exceptions can be handled in the following ways:
* Don't handle exceptions inside states of branches: in this case exceptions should be propagated to the
Parallel state and can be handled with the Parallel states "onError" definition, for example:
```json
{
"id": "exceptionInParallelState",
"name": "Exception In Parallel State",
"version": "1.0",
"functions": [
{
"name": "throwsExceptionFunction",
"resource": "throwExceptionFunctionResource"
}
],
"states": [
{
"name": "parallelState",
"type":"parallel",
"start": {
"kind":"default"
},
"completionType": "and",
"branches": [
{
"name": "invokeExceptionFunctionBranch",
"states": [
{
"name": "exceptionOperation",
"type":"operation",
"start": {
"kind":"default"
},
"actions": [
{
"functionRef": {
"refName": "throwsExceptionFunction"
}
}
],
"end": {
"kind":"default"
}
}
]
}
],
"onError": [
{
"expression": {
"language": "spel",
"body": "$.error ne null"
},
"transition": {
"nextState": "exceptionHandlingState"
}
}
],
"end": {
"kind": "default"
}
},
{
"name": "exceptionHandlingState",
"type":"operation",
"actionMode": "sequential",
"actions": [
],
"end": {
"kind":"default"
}
}
]
}
```
In this example our Parallel state branch the "throwsExceptionFunction" function execution throws an exception
which is propagated to the Parallel state and handled with its "onError" definition.
For the sake of the example we left the "actions" array of the "exceptionHandlingState" empty. In a real scenario
it would include actions needed to be executed.
* Handle exceptions inside branch states: States inside branches can define their own onError definition.
In this case the exceptions can be handled by the states and they will not be propagated to the Parallel state.
```json
{
"id": "errorInParallelState",
"name": "Error In Parallel State",
"version": "1.0",
"functions": [
{
"name": "ThrowsErrorFunction",
"resource": "throwErrorFunctionResource"
}
],
"states": [
{
"name": "parallelState",
"type":"parallel",
"start": {
"kind":"default"
},
"completionType": "and",
"branches": [
{
"name": "invokeFunctionBranch",
"states": [
{
"name": "exceptionOperation",
"type":"operation",
"start": {
"kind":"default"
},
"actions": [
{
"functionRef": {
"refName": "ThrowsErrorFunction"
}
}
],
"onError": [
{
"expression": {
"language": "spel",
"body": "$.error ne null"
},
"transition": {
"nextState": "errorHandlingBranchState"
}
}
],
"end": {
"kind":"default"
}
},
{
"name": "errorHandlingBranchState",
"type":"operation",
"actionMode": "sequential",
"actions": [
],
"end": {
"kind":"default"
}
}
]
}
],
"end": {
"kind": "default"
}
}
]
}
```
In this example the branches "exceptionOperation" state handles the thrown exception locally.
For the sake of the example we left the "actions" array of the "errorHandlingBranchState" empty. In a real scenario
it would include actions needed to be executed.
Action timeouts follow the same rules as stated above. They can be handled either by the branch states themselves, otherwise are to be propagated to the Parallel state.
For more information see the [workflow error handling and retrying section](#workflow-retrying).
#### SubFlow State
| Parameter | Description | Type | Required |