Building SDKs with clean architecture

Ever had to create one or more SDKs to expose your company’s services to other apps? We went through this process at babylon and we’re here to share the experience.

In this talk we’ll try to demonstrate how we went from a business decision of allowing the use of babylon services by 3rd party apps, to actually making this happen.

We’ll share some of the challenges and phases we went through to get there and how that impacted our code base.

Transcript

1. Building SDKs with clean
   architecture
   babylon Londroid April 2018
   Joao Alves and Sakis Kaliakoudas
   

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2. Babylon Services
   

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3. ● Partner agreement to ship
   babylon services as SDKs
   ● 2 months to ship initial
   versions
   ● 5 months for them to
   integrate
   ● 3 months of going through
   a multi phase QA
   Lift off
   

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4. ● Initial discussion
   ● Many parallel streams
   ● Usually 2 developers
   per SDK
   ● At most 4 teams
   working in parallel in
   different SDKs
   Planning
   

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5. How many SDKs?
   

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6. Babylon SDKs
   Appointments
   SDK
   Authentication
   SDK
   Consultation
   SDK
   User SDK NHS GP SDK Maps SDK
   Clinical
   Records SDK
   Payment SDK
   AI Chatbot
   SDK
   Monitor SDK
   Notifications
   SDK
   Common SDK
   Wrapper
   

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7. What did the code look like?
   

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8. Views Presenters Interactors
   Gateways/
   Repositories
   Retrofit
   Services
   Clean architecture layers
   

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9. Views Presenters Interactors
   Gateways/
   Repositories
   Retrofit
   Services
   What to ship?
   

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10. View related Domain
    Views Presenters Interactors
    Gateways/
    Repositories
    Retrofit
    Services
    What to ship?
    

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11. Views Presenters Interactors
    Gateways/
    Repositories
    Retrofit
    Services
    Legacy
    

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12. Views Presenters Interactors
    Gateways/
    Repositories
    Retrofit
    Services
    MVP
    

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13. Views Presenters Interactors
    Gateways/
    Repositories
    Retrofit
    Services
    MVP + Clean
    

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14. Moving stuff around
    App
    Gateways/
    Repositories
    Interactors Entities
    SDK 1
    SDK 2
    SDK N
    App
    Non-SDK
    Interactors
    Non-SDK
    Gateways
    SDK
    Gateways
    Entities
    

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15. Moving stuff around
    App
    Gateways/
    Repositories
    Interactors Entities
    App
    Non-SDK
    Interactors
    Non-SDK
    Gateways
    SDK
    Gateways
    Entities
    SDK 1
    SDK 2
    SDK N
    

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16. Moving stuff around
    App
    Gateways/
    Repositories
    Interactors Entities
    App
    Non-SDK
    Interactors
    Non-SDK
    Gateways
    SDK
    Gateways
    Entities
    SDK 1
    SDK 2
    SDK N
    

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17. Gateways and entities sharing
    SDK
    Gateways
    Entities
    SDK 1
    SDK 2
    SDK N
    

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18. Splitting it up
    Gateways 1
    Gateways 2
    Gateways N
    Entities
    SDK 1
    SDK 2
    SDK N
    

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19. class DoSomethingInteractor{
    private Gateway gateway;
    @Inject
    public DoSomethingInteractor(Gateway gateway){
    this.gateway = gateway;
    }
    Disposable execute(Request request, Callback callback){
    ...
    }
    }
    But what does it look like
    

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20. interface Callback{
    void onSuccess(Result result);
    void onError(Exception exception);
    }
    class Request {
    String someField1;
    String someField2;
    }
    class Result {
    String someField3;
    String someField4;
    }
    But what does it look like
    

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21. class DoSomethingInteractor{
    private Gateway gateway;
    @Inject
    public DoSomethingInteractor(Gateway gateway){
    this.gateway = gateway;
    }
    Disposable execute(Request request, Callback callback){
    ...
    }
    }
    But what does it look like
    

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22. Client
    Clinical
    Records
    SDK
    Wrapping the interactors
    ClinicalRecordsApi clinicalRecordsApi = ClinicalRecordsSdk.getApiInstance();
    clinicalRecordsApi.doSomething(request, callback);
    Client requests an instance of the API
    

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23. Clinical
    Records API
    Client
    Clinical
    Records
    SDK
    Wrapping the interactors
    ClinicalRecordsApi clinicalRecordsApi = ClinicalRecordsSdk.getApiInstance();
    clinicalRecordsApi.doSomething(request, callback);
    The SDK class instantiates the API
    

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24. Clinical
    Records API
    Client
    Clinical
    Records
    SDK
    Wrapping the interactors
    ClinicalRecordsApi clinicalRecordsApi = ClinicalRecordsSdk.getApiInstance();
    clinicalRecordsApi.doSomething(request, callback);
    Returns it to the client
    

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25. Clinical
    Records API
    Interactors
    Interactors
    Interactors
    Gateways
    Interactors
    Entities
    Client
    Clinical
    Records
    SDK
    Wrapping the interactors
    ClinicalRecordsApi clinicalRecordsApi = ClinicalRecordsSdk.getApiInstance();
    clinicalRecordsApi.doSomething(request, callback);
    Client can access all the SDK interactors via the API
    

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26. SDK API Interface
    /**
    * Get list of appointments for the main user and its registered children
    * (if any).
    *
    * @param request the request object that contains the required information
    * to get the user appointments.
    * @param output the callback through which the results are returned.
    *
    * @return an RxJava 2 {@link Disposable} resource to manage this request.
    */
    Disposable getAppointments(GetAppointmentsRequest request, GetAppointmentsOutput output);
    

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27. String patientId = "patientId";
    GetAppointmentsRequest request =
    GetAppointmentsRequest.create(AppointmentType.UPCOMING, patientId);
    babylonAppointmentApi.getAppointments(request, new GetAppointmentsOutput() {
    @Override
    public void onFetchAppointmentsSuccess(List appointments) {
    if (appointments.isEmpty()) {
    getView().showNoAppointments();
    } else {
    getView().showAppointments(appointments);
    }
    }});
    Presenter using the SDK:
    

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28. Dog fooding
    ● Using the SDKs inside our
    Apps
    ● Local development with local
    gradle module dependencies
    ● CI builds the SDKs, publishes
    them, then builds the app
    using artifact dependencies
    

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29. Build and deploy
    Local Maven
    Repo
    Artifactory
    Single Gradle
    Task
    ● ~25 releases in 10 months (excluding hotfixes)
    ● Releases around every 10 days
    a day an hour a minute
    

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30. Security
    ● No sensitive information
    stored locally
    ● Encryption with Android
    keystore
    ● Using Dexguard
    ● Logging based on
    environment
    ● Timber Wrapper
    

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31. Uniquely identifying clients via their public certificate
    Offline:
    ● Get certificate hash
    ● Merge it together with the application id to generate a new hash
    ● Save this hash inside the SDKs
    Runtime:
    ● Calculate the same hash
    ● Match it against the precomputed value
    

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32. Activities in the SDKs?
    

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33. Kotlin?
    

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34. SDK size
    ● Trimming all dependencies
    ● Native libraries
    ● Dexguard
    

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35. Documentation
    ● JavaDoc with CheckStyle
    ● Release notes - from git diff to
    git code owners
    ● Sample App
    ● Wiki page
    

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36. Support
    ● Slack support
    ● Dedicated JIRA board
    ● Daily/Weekly calls
    

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37. Finish line
    ● Improved code quality
    ● Much less legacy code
    ● Modularized project
    ● Loads of knowledge
    ● Much bigger user base
    

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38. What does the code look like now?
    

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39. Lessons learned
    ● Planning + Planning +
    Planning
    ● Don’t create silos - merge
    often
    ● More logging
    ● Version controlled
    documentation
    

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40. ● Problems are bound to
    happen and trust us they
    will happen. And they
    don’t come on their own
    they come in herds.
    ● Work your way through
    them and you’ll eventually
    get to the finish line.
    Don’t Panic
    

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41. Questions?
    Presented by Joao Alves and Sakis Kaliakoudas
    Say hi on Twitter & Medium:
    @jcmsalves & @skaliakoudas
    PS: we’re hiring, come and talk to us to know more
    

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42. Useful links
    ● SDK class example: (https://tinyurl.com/MyBossMadeMeDoThis)
    ● Getting a certificate hash (https://tinyurl.com/tralalatralalo)
    ● Merging a certificate hash with an application id to generate a new hash
    (https://tinyurl.com/we-r-hiringgg)
    ● Calculating the same hash at runtime (https://tinyurl.com/PleaseDontAskQuestions)
    

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