Process Orchestration with Flowable and Spring Boot

Process orchestration with Flowable and Spring Boot Chavdar Baykov Solution Architect (Digital Wallets) Paysafe Group

About Me • Solution Architect in Paysafe Group • Digital Wallets • 20+ years of Software Development experience • Java & Backend Services • Business Process Analytics • Cloud PaaS & SaaS • In my free time I like to • Spend time with the family • Watch movies • Play with tech gadgets

“ ” A series of actions or steps taken in order to achieve a particular end. We may not realize it, but processes are everywhere and in every aspect of our leisure and work What is a Process ?

Implementing Processes using Microservices Orchestration Choreography

Orchestration vs Choreography Orchestration • Process Engine node manages execution • Considered SPOF and bottleneck • Prone to increase of complexity • Process-agnostic services • Do not know their place in the process • Less prone to change • Process ownership • Distributed vertically • Issues fixed in the orchestrator instead in services Choreography • No central process • No SPOF and considered more scalable • Smart Services • Know their role in the process • Prone to change and increase in complexity • Process ownership • Lack of the ‘whole picture’ • Distributed horizontally across teams • Services are up, but process is broken effect

Hybrid Approach • Orchestration in Business Domains • micro-orchestrators • End-to-end process ownership • Choreography across Business Domains • Responsibility boundaries • More Stable contract • Less context required • Examples: • Know Your Customer processes • Customer levels processes

Introducing • Compact and highly efficient workflow and BPM platform (Process Engine) • Written in Java • Free Open Source • Apache 2.0 License • Can run • Embedded or on Dedicated servers • Clustered • Cloud or Locally • Highly customizable and pluggable • Only one required dependency • Database

Flowable Architecture • Persistency engine (MyBatis) • H2, Oracle, PostgreSQL, MySQL • Services • Segregated by functionality for each Engine • Engines • BPMN, CMMN, DMN, Form, Content • REST API • Flowable Applications • Modeler, Task , IDM, Admin

When is appropriate ? • Java ecosystem • Process as part of the service • Orchestrator role • Drives and tracks the business processes in some domain • Orchestrate single purpose microservices • Shared services • Embedded engine benefits • Allows some business logic to run embedded • Test driven development

Flowable and Spring • Spring Boot property-based auto configuration • https://flowable.com/open-source/docs/bpmn/ch05a-Spring-Boot/ • All expressions in the BPMN processes will also 'see' all the Spring beans, by default. • what Beans Flowable ‘see’ is configurable • Unit & Integrating testing • H2 in-memory database by default • Spring Boot tests – for Deployment, Configuration and Bindings • Spring tests - for Testing Flow logic with Mocked Task implementations • Unit test - for tasks and services

Process Definition • Describe the process steps • Tasks • Flows • Gateways • BPMN 2.0 XML format • each node has id • flowable extension elements • Diagram element contains visual metadata • Executions are called Process Instances • Instance state is stored in Process Context

Start Event • Indicates where process starts • Process start through API • Other Start Event Types (Triggers) • Timer Start Event • Signal Start Event • Message Start Event • Graphical Notation • XML Representation

Sequence Flow • Connector between elements • sourceRef - start element reference • targetRef – end element reference • Conditional Sequence Flow • Continues only if expression evaluates to TRUE • Graphical Notation • XML Representation

Java Service Task • Invokes a Java logic implementing a task • Can invoke • class – Java Class • delegateExpression - Java Bean • expression - Java Bean method • Use to orchestrate internal and external logic • Graphical Notation • XML Representation

Implementing Java Service Tasks • Not Instantiated During Deployment • Unit test them to prevent runtime errors • Stateless • Get and store state in Process Context (or somewhere else) • Retriable (if configured) • Short Running Tasks (sync, in transaction) • Implement org.flowable.engine.delegate.JavaDelegate • Long Running Tasks (async, out of transaction) • Implement org.flowable.engine.delegate.FutureJavaDelegate

User Task • Task, that needs to be done by Human • Execution stops until task is completed • Actual task logic is outside of the engine • API to query tasks • API to complete tasks • Might be assigned (delegated) to • Users • Groups of Users • Graphical Notation • XML Representation

End Event • End of a process path • Terminate End Event • Terminates the process instance • Graphical Notation • XML Representation

Parallel Gateway • Model concurrency in a process • fork – all outgoing sequence flows executed • join – wait until all incoming flows arrive • Conditions on incoming and outgoing flows are ignored • Graphical Notation • XML Representation

Exclusive Gateway • Model a decision in the process (XOR) • Only One sequence flow is executed • Expression must evaluate to TRUE • Execute first defined if multiple evaluate true • Graphical Notation • XML Representation 

Process Deployment • Process packaged in the Application • Activates the updated Process • Only deploys if there are changes • Automatic versioning • All referenced classes must exist • Watch out for cluster consistency issues • Trigger deploy after update is finished • Spring Auto Deployment • Deployment through API

Demo: Verified Phone Registration Process • Build a microservice, that provides verified phone registration • The phone validation process happens through secret token • Delivered as SMS (mocked) • 60 seconds validity • User should input the received token to complete the process • User can re-generate token (invalidating the old token) up to 3 times • User can abandon the process at any time • Existing microservices (mocked) • SMS Delivery, User Profile, eMail Delivery

Verified Phone Registration Process

Verified Phone Registration REST API • Create phone registration • POST /user/phone/registration/{userId} • Get ongoing phone registrations for User • GET /user/phone/registration/{userId} • Create new token for registration • POST /user/phone/registration/{userId}/{registrationId} • Submit token for registration • POST /user/phone/registration/{userId}/{registrationId}/token

Flowable Best Practices • Unit & Integration test the processes • Decouple interactions with process engine classes • Store only what is needed in the context • Optimize the process for execution and reliability • Fetch dependencies earlier, do modification later in the process • Serialize complex objects as JSON in context • Move business logic out of tasks • Services might be reusable, but tasks are not! • Add Error Handling to processes • Failed processes must complete at some point • Take care of process history

Thank you! Контакти Чавдар Байков chavdarb@yahoo.com LinkedIn https://www.linkedin.com/in/chavdar-baykov-8322385/ Github https://github.com/chavdarb Следващо събитие: Test Coverage: Why, What, Who, How

Resource Links • Flowable Home • https://flowable.com/open-source/ • Flowable Spring Boot Samples • https://github.com/flowable/flowable-engine/tree/master/modules/flowable-spring-boot/flowable- spring-boot-samples • Phone Registration Sample Application (Presentation Demo) • https://github.com/chavdarb/flowable-phone-registration-demo • Introduction to Flowable • https://www.baeldung.com/flowable

Process Orchestration with Flowable and Spring Boot

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