Microservices with Netflix OSS & Hypermedia APIs - JavaDay Kiev
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At a major telco company in Belgium we have designed and implemented a cutting-edge architecture using microservices and hypermedia (REST level 3 / hateoas) for the entire customer- and business-facing web portfolio. Throughout this session you will learn what the microservices hype is all about, including its benefits and pitfalls based on our experiences of running microservices (including the Netflix OSS) in production at a major company in Belgium. To manage hundreds of microservices you need to apply certain patterns such as circuit breakers, gateways, service registries and so on. You will learn how these patterns work, how they are applied through the Netflix stack and how easy it is to use them in your architecture through code examples and demos. The contracts between these microservices should be well defined and loosely coupled. Using hypermedia as the engine of application state (hateoas), we can benefit from independent evolution and decoupled implementation. How we can implement these using Spring Hateoas, correctly document using Spring Restdocs, integrate with the HAL browser and version using JsonViews will become clear in the second part of this session.
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Microservices with Netflix OSS & Hypermedia APIs - JavaDay Kiev
- 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? • Surgical Routing
- 10. @andreasevers • Surgical Routing • Stress Testing • Canary Testing Gateway – What’s the use?
- 11. @andreasevers Gateway µS µS µS µS µSµS
- 12. @andreasevers • Surgical Routing • Stress Testing • Canary Testing • Request authentication & authorization • Choosing origin servers Gateway – What’s the use?
- 13. @andreasevers • Surgical Routing • Stress Testing • Canary Testing • Request authentication & authorization • Choosing origin servers • Routing the request to an origin • Logging debug info • Adding headers to the request and response • Gathering statistics and metrics • Filter error handling • Generate static responses Gateway – What’s the use?
- 14. @andreasevers • Surgical Routing • Stress Testing • Canary Testing • Request authentication & authorization • Choosing origin servers • Routing the request to an origin • Logging debug info • Adding headers to the request and response • Gathering statistics and metrics • Filter error handling • Generate static responses • Load Shedding Gateway – What’s the use?
- 15. @andreasevers • Surgical Routing • Stress Testing • Canary Testing • Request authentication & authorization • Choosing origin servers • Routing the request to an origin • Logging debug info • Adding headers to the request and response • Gathering statistics and metrics • Filter error handling • Generate static responses • Load Shedding • Dynamic behavior change Gateway – What’s the use?
- 16. @andreasevers
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- 19. @andreasevers Service Registry Service Registry loyalty user billing billing’ loyalty user user origin Origin 1 Origin 2billing loyalty origin
- 20. @andreasevers Service Registry Service Registry loyalty user billing billing’ loyalty user billing user origin Origin 1 Origin 2 loyalty origin
- 21. @andreasevers billing Service Registry Service Registry loyalty billing billing’ loyalty user user origin loyalty origin Origin 1 user billing’ billing Origin 2
- 22. @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
- 24. @andreasevers
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- 28. @andreasevers Circuit Breaker Gateway µS customer µS user µS loyaltyµS customer µS loyalty Backends
- 29. @andreasevers Circuit Breaker - Fallbacks
- 31. @andreasevers Circuit Breaker - Dashboard
- 32. @andreasevers Circuit Breaker - Dashboard
- 33. @andreasevers Circuit Breaker - Dashboard
- 43. @andreasevers Contracts & loose coupling We can achieve this by using Hypermedia
- 45. @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
- 46. @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
- 47. @andreasevers Why Hateoas? • Updating server-side web APIs only to learn that client applications no longer work as expected without undergoing code updates • Moving long-lived server applications to a new DNS name (e.g. from www.belgacom.be to www.proximus.be) and having to completely rewrite all of the API documentation as well as update all existing client code with all its links to the server’s APIs • Implementing new or modified process flow within the server-side application and discovering that existing clients break when encountering the new rules, ignore the rules, or, worse, continue to execute their own code in a way that creates invalid results on the server
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- 54. @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
- 55. @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
- 56. @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”
- 57. @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?
- 58. @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>
- 59. @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>
- 60. @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
- 61. @andreasevers Hateoas Benefit: Non-structural Changes “customers/1/accounts/1/products/1234” auto-discoverable through HATEOAS as “customers[1].accounts[1].products[1234]” will not break when 1234 as id is changed to “basementNerd”
- 62. @andreasevers Hateoas Concern: Structural Changes “customers/1/accounts/1/products/1234” auto-discoverable through HATEOAS as “customers[1].accounts[1].products[1234]” could break when accounts are bypassed
- 63. @andreasevers Hateoas Benefit: Changing the URI of a resource “customers/1/accounts/1/products/1234” being returned as part as the response body of “customers/1/accounts/1” will not break the client
- 64. @andreasevers Content Types "text/html" • Browsers know how to parse it • Browsers understand keywords inside it • E.g: a + href , form + action + method , ... "application/json" or "application/xml“ • Clients know how to parse it • Clients don’t understand keywords inside it • Needs a uniform format as communication between client & server • Needs a reference for out-of-bound (api-specific) keywords
- 65. @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
- 66. @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.
- 69. @andreasevers What should you document Resources Links Cross-cutting concerns
- 70. @andreasevers What shouldn’t you document URIs
- 71. @andreasevers What does it look like when you get it wrong?
- 72. @andreasevers What does it look like when you get it right?
- 77. @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
- 78. @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