Netflix OSS and HATEOAS deployed on production - JavaLand
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The document discusses the benefits and pitfalls of using microservices, particularly within a Netflix open-source context, emphasizing the importance of adopting a contract-first approach and the role of API gateways. It explains the concept of HATEOAS (Hypermedia as the Engine of Application State) and its advantages for runtime action discovery and non-structural changes in an API. Additionally, it covers documentation best practices and the limitations of tools like Swagger in relation to hypermedia support.
![@andreasevers
Hateoas Benefit: Non-structural Changes
“categories/1/oil-paintings/1234”
auto-discoverable through HATEOAS as
“categories[1].oil-paintings[1234]”
will not break when 1234 as id is changed to “basementNerd”](https://image.slidesharecdn.com/netflixossandhateoasdeployedonproduction-160311133311/85/Netflix-OSS-and-HATEOAS-deployed-on-production-JavaLand-54-320.jpg)
Netflix OSS and HATEOAS deployed on production - JavaLand
- 1. @andreasevers Netflix OSS and HATEOAS deployed on production
- 2. @andreasevers WHOAMI • Work for Ordina Belgium • Open source enthusiast • Spring contributor • Speaker • Technical lead & coding architect @ Proximus • Marathon runner
- 4. @andreasevers Benefits • Small, easy to understand code base • Easy to scale • Easy to throw away • Easy to deploy • Ability to use a different technology stack • Smaller teams • System resilience
- 5. @andreasevers Pitfalls “If you can't build a monolith, what makes you think microservices are the answer?” Simon Brown
- 6. @andreasevers Pitfalls • Failing to adopt a contract-first approach • Assuming the wrong communication protocol • Introducing a shared domain model • Defining inappropriate service boundaries • Neglecting DevOps and testing concerns • Disregarding the human factor • Operational complexity not under control • Failing to embrace eventual consistency
- 9. @andreasevers Gateway – What’s the use?
- 10. @andreasevers Gateway µS µS µS µS µSµS
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- 14. @andreasevers “API Gateways are fast becoming the Enterprise Service Bus of the microservices era” Sam Newman Gateway
- 15. @andreasevers Service Registry Service Registry loyalty user billing billing’ loyalty user user origin Origin 1 Origin 2billing loyalty origin
- 16. @andreasevers Service Registry Service Registry loyalty user billing billing’ loyalty user billing user origin Origin 1 Origin 2 loyalty origin
- 17. @andreasevers billing Service Registry Service Registry loyalty billing billing’ loyalty user user origin loyalty origin Origin 1 user billing’ billing Origin 2
- 18. @andreasevers Service Registry Service Registry loyalty user user origin loyalty origin Origin 1billing Origin 2 Service Registry loyalty user user origin loyalty origin Origin 1billing Origin 2 loyalty Cached Registry
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- 25. @andreasevers Circuit Breaker - Dashboard
- 26. @andreasevers Circuit Breaker - Dashboard
- 36. @andreasevers Contracts & loose coupling We can achieve this by using Hypermedia
- 38. @andreasevers Hypermedia h8ps://vimeo.com/20781278 Sub-constraints: • IdenDficaDon of resources (URIs) • ManipulaDon via representaDons (request & response bodies) • Self-descripDve messages (headers) • Hypermedia as the engine of applicaDon state HTTP as applica+on protocol
- 39. @andreasevers Hypermedia h8ps://vimeo.com/20781278 Sub-constraints: • IdenDficaDon of resources (URIs) • ManipulaDon via representaDons (request & response bodies) • Self-descripDve messages (headers) • Hypermedia as the engine of applicaDon state If you don’t do this Then you don’t adhere to this And you are missing out on these
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- 47. @andreasevers Hateoas in action How would you explain to a client to get to the Nerd in the Basement painting? A. Go to Amazon.com, in the categories go to fine arts, follow paintings, more specifically oil paintings, and click on the one with the title Nerd in the Basement B. Type http://www.amazon.com/Nerd-in-the-Basement/dp/ B00L849CSS/ref=lp_6685279011_1_2? s=art&ie=UTF8&qid=1431864368&sr=1-2 in your browser
- 48. @andreasevers Hateoas in action HTML is a hypermedia format <a> is a link with method GET <form> is a link with method POST (or other if specified) The browser understands this syntax and shows a link or a form if the server response contains these tags
- 49. @andreasevers Hateoas Requirements Communication between Client and Server depends on: • Where does the client have to start? • Root API • In regular websites: the homepage • Where am I? • How do I interpret the current API response? • In regular websites: the syntax of HTML is interpreted by the browser • Where can I go? • What does a link or form with a certain relation or class mean? • In regular websites: link with relation “stylesheet”, form with action “login”
- 50. @andreasevers Hateoas in action Amazon.com (and any other website in the whole world wide web) applies Hateoas. Why wouldn’t your API do the same?
- 51. @andreasevers Hateoas Benefit: Runtime action discovery GET /account/12345 HTTP/1.1 HTTP/1.1 200 OK <?xml version="1.0"?> <account> <account_number>12345</account_number> <balance currency="usd">100.00</balance> <link rel="deposit" href="/account/12345/deposit" /> <link rel="withdraw" href="/account/12345/withdraw" /> <link rel="transfer" href="/account/12345/transfer" /> <link rel="close" href="/account/12345/close" /> </account>
- 52. @andreasevers Hateoas Benefit: Runtime operation discovery GET /account/12345 HTTP/1.1 HTTP/1.1 200 OK <?xml version="1.0"?> <account> <account_number>12345</account_number> <balance currency="usd">-25.00</balance> <link rel="deposit" href="/account/12345/ deposit" /> </account>
- 53. @andreasevers Hateoas Concern: Scope In case of one or two clients built in the same team, it is arguable whether auto-discoverability is really a necessity
- 54. @andreasevers Hateoas Benefit: Non-structural Changes “categories/1/oil-paintings/1234” auto-discoverable through HATEOAS as “categories[1].oil-paintings[1234]” will not break when 1234 as id is changed to “basementNerd”
- 55. @andreasevers Hateoas Benefit: Changing the URI of a resource “categories/1/oil-paitings/1234” being returned as part as the response body of “categories/1” will not break the client
- 56. @andreasevers Content Types • JSON • NOT hypermedia-aware by default • Needs a fixed format to support links and forms • Many formats available • XHTML • IS hypermedia-aware by default • Harder to process XHTML responses using javascript (xpath is required) • The API responses can also be read by a human as regular HTML pages • SVG, Atom, HTML • Similar as XHTML but not preferred
- 57. @andreasevers JSON Formats • JSON-LD • Augmenting existing APIs without introducing breaking changes • Needs HYDRA as a vocabulary for communicating operations • Decoupling of API serialization format & communication format • HAL • Minimal, light weight syntax and semantics • Offers most of the benefits of using a hypermedia type • Easy to convert existing API to HATEOAS • Chosen and supported by Spring • No support for specifying operations • Collection+JSON • Can list queries that your collection supports and templates that clients can use to alter your collection • Great for publishing user editable data • SIREN • Represents generic classes of items • Supports operations • Concept of classes, bringing a sense of type information to your API responses
- 60. @andreasevers What should you document Resources Links Cross-cutting concerns
- 61. @andreasevers What shouldn’t you document URIs
- 62. @andreasevers What does it look like when you get it wrong?
- 63. @andreasevers What does it look like when you get it right?
- 68. @andreasevers Best practices for documentation Write as much as possible in a format which is designed for writing Don’t use the implementation to provide the documentation Provide some guarantees that the documentation is accurate h8ps://github.com/spring-projects/spring-restdocs
- 69. @andreasevers Thank you for your attention @andreasevers https://github.com/oraj-360 http://registry.oraj360.cfapps.io/ https://netflix.github.io/ http://projects.spring.io/spring-cloud/ http://projects.spring.io/spring-hateoas/ https://github.com/spring-projects/spring-restdocs