Baker is a Scala library that simplifies the development of complex orchestration logic through defining recipes with ingredients, events and interactions. The recipes are compiled into a Petri net model for validation and execution. Baker handles runtime execution of recipes using Akka actors for event sourcing, persistence and concurrency. It provides features like compile-time validation, type safety, parallel execution and automatic retries. Property based testing is also supported to validate recipes.

1. Bekir Oguz
Merlijn van Ittersum
Designing process flows with
#Baker
Amsterdam.Scala Meetup
September 2017

2. How to bake a pizza?
2

3. How to bake a pizza?
3

4. How to bake a pizza?
4

5. Why?

6. It is hard to develop complex orchestration APIs
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8. We need a cleaner way to allow design changes in complex APIs
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Example: initial design of the API
A B C D E
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9. A B C D E
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We need a cleaner way to allow design changes in complex APIs
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Example: API after one design change

10. A B C D E
1 2 3 4 5
We need a cleaner way to allow design changes in complex APIs
10
Example: API after ten design changes

11. We need a cleaner way to allow design changes in complex APIs
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Example: API after ten design changes
A B C D E
1 2 3 4 5

12. Open Kinder- / Jongerenrekening Open Groei Groter rekening Another Product
Verify customer rules Verify customer rules Verify customer rules
Register individual Register individual Register Individual
Send a present Send a present Not applicable
Send a message to the customer Send a message to the customer Send a message to the customer
Open a payments account Open a savings account Open a payments account
Enable billing Enable billing Assign package
There is more need for reuse between teams
12

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What?

14. Baker is a Scala library that simplifies the development of complex orchestration logic.
What? Baker!
github.com/ing-bank/baker

15. Intermediate
Languagevalidate
compile
execute
Baker runtime

16. Recipe
Event
Ingredient
Interaction

17. Defining ingredients
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case class CustomerInfo(name: String, address: String, email: String)
// ingredients
val customerInfo = Ingredient[CustomerInfo]("customerInfo")
val trackingId = Ingredient[String]("trackingId")
val order = Ingredient[String]("order")

18. Defining events
18
// events
val goodsShipped = Event("GoodsShipped", trackingId)
val orderPlaced = Event("OrderPlaced", order)
val paymentMade = Event("PaymentMade")
val valid = Event("Valid")
val sorry = Event("Sorry")

19. Defining interactions
19
// interactions
val validateOrder = Interaction(
name = "ValidateOrder",
inputIngredients = order,
output = FiresOneOfEvents(valid, sorry)
)
val shipGoods = Interaction(
name = "ShipGoods",
inputIngredients = Ingredients(goods, customerInfo),
output = FiresOneOfEvents(goodsShipped)
)

20. Defining a recipe
20
// recipe
val webShopRecipe: Recipe =
Recipe("WebShop")
.withInteractions(
validateOrder,
manufactureGoods
.withRequiredEvents(valid, paymentMade),
shipGoods,
sendInvoice
.withRequiredEvent(goodsShipped)
)
.withSensoryEvents(
customerInfoReceived,
orderPlaced,
paymentMade)

21. Compile the recipe
21
// compiles the recipe
val compiledRecipe = RecipeCompiler.compileRecipe(webShopRecipe)
// list of validation errors
val errors: Seq[String] = compiledRecipe.validationErrors
// .dot (graphviz notation) representation
val visualization: String = compiledRecipe.getRecipeVisualization

22. Visualising the recipe
22

23. A Baker instance can be created from the valid recipe.
It takes care of the execution of the recipe.
The only thing left is to provide sensory events to Baker!
Baker runtime
23

24. Initializing Baker instance
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You can create a new Baker instance by providing the recipe and implementations of the
interactions:
val compiledRecipe = RecipeCompiler.compileRecipe(webShopRecipe)
val validateOrderImpl = validateOrder implement {
(order: String) => {
// Some logic here
valid.instance() // or maybe invalid event to be returned
}
}
val implementations =
Seq(validateOrderImpl, manufactureGoodsImpl, sendInvoiceImpl, shipGoodsImpl)
val baker = new Baker(compiledRecipe, implementations)

25. For each client request you do the following:
Firing events
25
val processId = UUID.randomUUID().toString
baker.bake(processId)
baker.handleEvent(processId, orderPlaced.instance(testOrder))
baker.handleEvent(processId, paymentMade.instance())
baker.handleEvent(processId, customerInfoReceived.instance(testCustomerInfoData))
val actualIngredients: Map[String, Any] = baker.getIngredients(processId)
val actualEvents: Seq[RuntimeEvent] = baker.events(processId)

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42. 1. It is hard to develop complex orchestration APIs
2. We need a cleaner way to allow design changes in complex APIs
3. There is more need for reuse between teams
Does Baker help with the Why?
42

43. 1. It is hard to develop complex orchestration APIs
With Baker, you think about what you want, not about the order.
Baker can validate the recipe for you.
Clear insight in the current model by visualising the recipe.
2. We need a cleaner way to allow design changes in complex APIs
3. There is more need for reuse between teams
Does Baker help with the Why?
43

44. 1. It is hard to develop complex orchestration APIs
With Baker, you think about what you want, not about the order.
Baker can validate the recipe for you.
Clear insight in the current model by visualising the recipe.
2. We need a cleaner way to allow design changes in complex APIs
Baker links the interactions when compiling the recipe.
If interactions are added, removed or changed, Baker will update the model accordingly.
3. There is more need for reuse between teams
Does Baker help with the Why?
44

45. 1. It is hard to develop complex orchestration APIs
With Baker, you think about what you want, not about the order.
Baker can validate the recipe for you.
Clear insight in the current model by visualising the recipe.
2. We need a cleaner way to allow design changes in complex APIs
Baker links the interactions when compiling the recipe.
If interactions are added, removed or changed, Baker will update the model accordingly.
3. There is more need for reuse between teams
The possibility to share interactions, ingredients and events between recipes allows for
much more reuse of code among teams.
Does Baker help with the Why?
45

46. How?

47. Baker is powered by
47
PetriNet

48. Process logic is isolated in an Akka actor, this gives us the following benefits:
• Event sourcing through persistent actors
• Supporting many data stores, i.e. cassandra
• Distributing actors with Cluster Sharding
Akka
48

49. On creation of the Baker instance, the recipe is compiled into a Petri net.
A Petri net is a mathematical model that can be used for reasoning about concurrency.
This Petri net is then used to determine when & what interactions to execute.
PetriNet
49

50. Execution Semantics: Token passing
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51. Execution Semantics: Token passing
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t1 t2 t3

52. Execution Semantics: Token passing
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t1 t2 t3

53. Execution Semantics: Token passing
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t1 t2 t3

54. Execution Semantics: Concurrency
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t1
t3
t4
t5
t2

55. Execution Semantics: Concurrency
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t1
t3
t4
t5
t2
Choice

56. Execution Semantics: Concurrency
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t1
t3
t4
t5
t2
Parallel split

57. Execution Semantics: Concurrency
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t1
t3
t4
t5
t2
Parallel paths

58. Execution Semantics: Concurrency
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t1
t3
t4
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t2
Parallel paths

59. Execution Semantics: Concurrency
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t1
t3
t4
t5
t2
synchronization

60. • Simple, uses only a few concepts and components
• Exact mathematical definition of execution semantics
• Intuitive graphical notation
• Well-developed mathematical theory for process analysis
Advantages
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61. Reachability
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?
A
B

62. Unreachable code
62
A
B

63. Detect cycles
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64. Path traversal time
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Average traversal time: 10 seconds
A
B

65. Identifying bottlenecks
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Takes 70% of the time
A
B

66. Path prediction
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83%
17%
A
B

67. 67
Features
Recipe Runtime

68. 68
Features
Recipe
Developer friendly Java/Scala dsl
Runtime

69. 69
Features
Recipe
Developer friendly Java/Scala dsl
Compile-time recipe validation
Runtime

70. 70
Features
Recipe
Developer friendly Java/Scala dsl
Compile-time recipe validation
Type safety
Runtime

71. 71
Features
Recipe
Developer friendly Java/Scala dsl
Compile-time recipe validation
Type safety
Runtime
Execution of the recipe, powered by
akka and petrinet model

72. 72
Features
Recipe
Developer friendly Java/Scala dsl
Compile-time recipe validation
Type safety
Runtime
Execution of the recipe, powered by
akka and petrinet model
Persisted state through event sourcing

73. 73
Features
Recipe
Developer friendly Java/Scala dsl
Compile-time recipe validation
Type safety
Runtime
Execution of the recipe, powered by
akka and petrinet model
Persisted state through event sourcing
Data encryption

74. 74
Features
Recipe
Developer friendly Java/Scala dsl
Compile-time recipe validation
Type safety
Runtime
Execution of the recipe, powered by
akka and petrinet model
Persisted state through event sourcing
Data encryption
Automatic retries on technical failures

75. 75
Features
Recipe
Developer friendly Java/Scala dsl
Compile-time recipe validation
Type safety
Runtime
Execution of the recipe, powered by
akka and petrinet model
Persisted state through event sourcing
Data encryption
Automatic retries on technical failures
Parallel execution of paths

76. Property Based Testing
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77. Property Based Testing
77
val recipeGen: Gen[Recipe] = for {
name <- nameGen
sensoryEvents <- Gen.listOf(eventGen) suchThat (_.nonEmpty)
interactions <- interactionsGen(sensoryEvents) suchThat (_.nonEmpty)
} yield Recipe(name)
//turn the lists into var args
.withSensoryEvents(sensoryEvents: _*)
.withInteractions(interactions.toList: _*)

78. Property Based Testing
78
forAll(recipeGen) { recipe =>
val validations = ValidationSettings(
allowCycles = false,
allowNonExecutableInteractions = false)
val compiledRecipe = RecipeCompiler.compileRecipe(recipe, validations)
if (compiledRecipe.validationErrors.nonEmpty) {
logRecipeStats(recipe)
logCompiledRecipeStats(compiledRecipe)
}
compiledRecipe.validationErrors.isEmpty
}

79. Questions?