university of washington - the new api pattern

The New API Pattern

Owen Rubel [email protected]

mailto:[email protected]?subject=

Title TextFirst Lets Understand The Difference Between Centralized and Distributed Architectures…

Understanding The API Pattern



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Centralized vs Distributed Architecture

Centralized Architecture (Unshared I/O)

Distributed Architecture (Shared I/O)

microservices

monolith application

monolith application

proxy MQappserver


Client Client

ClientClient

(CORS,security) (caching,security)


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• How many developers still use a centralized architecture vs a distributed architecture in their development?



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• How many developers used a centralized architecture for their development 5 years ago? 10 years ago?



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• How many developers used a centralized architecture for their development 5 years ago? 10 years ago?

• Over the last 20+ years, there has been a trend toward distributed architectures due to separation of services/concerns, micro services, and Aspect Oriented Programming



Title Text“ An API is Standardized Input/Output (I/O) to/from a Separation of Concern (usually being Business Logic).”

In Short :

What Is An API? (1 OF 2)



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What Is An API? (2 OF 2)



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“ In computer science, separation of concerns (SoC) is a design principle for separating a computer program into distinct sections, such that each section addresses a separate concern. A concern is a set of information that affects the code of a computer program” (ex HTML, CSS, JS)

- Source : Separation Of Concern, Wikipedia

What Is Separation of Concern? (1 of 2)



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What Is Separation of Concern? (2 of 2)

Bound SecondaryConcern

(Communication Logic)

PrimaryConcern

(Business Logic)



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API Pattern in Distributed Architecture

Bound I/O Dataand/or Functionality



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!!!WARNING!!! CROSS CUTTING CONCERN

API Pattern in Distributed Architecture

Bound I/O Dataand/or Functionality

Duplicated I/O Dataand/or Functionality

Duplicated I/O Dataand/or Functionality



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“Cross-cutting concerns can be directly responsible for tangling, or system inter-dependencies, within a program. Because procedural and functional language constructs consist entirely of procedure calling, there is no semantic through where two goals (the capability to be implemented and the related cross-cutting concern) can be addressed simultaneously.[3] As a result, the code addressing the cross-cutting concern must be scattered, or duplicated, across the various related locations, resulting in a loss of modularity.[2]”

- Source : Cross Cutting Concern, Wikipedia

What is a Cross Cutting Concern?



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• Synchronization • Real-time constraints• Error detection and correction• Product features• Memory management• Data validation • Persistence • Transaction processing• Internationalization and localization which includes

Language localisation• Information security• Caching• Logging • Monitoring• Business rules • Code mobility• Domain-specific optimizations

Issues of a Cross Cutting Concern



Title TextThis is The API Patterns Brick Wall

Brick Wall



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• API’s were created in 70’s to standardize information exchanged between services

• 70’s api pattern was designed for centralized architecture; distributed architectures didn't exist.

• Web API’s were based on 70’s api pattern; Roy Fielding based his dissertation on this pre-existing pattern.

• Web API’s were integrated into MVC frameworks and tools; it is now used everywhere.

Why Did This Happen? (1 of 2)



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• Distributed Architectures are a New Pattern. Old principles and patterns are often not re-examined unless an issue is discovered. In the case of API’s, they are a tried and true pattern and still work locally… but not ‘distributed’

• People ASSUMED the resource was the endpoint; The controller hands the resource OFF to the communication layer. The communication layer hands off I/O to other services in a distributed architecture. Hence, the communication layer is the endpoint.

Why Did This Happen? (2 of 2)



Title TextSo How Do We Fix?

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Old API Pattern in MVC


redirect/response


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New API Pattern in MVC



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Shared I/O State In Distributed Architecture



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This allows:

• Central Piece of architecture (where REQUEST AND RESPONSE are handled) to be ‘Single Version of Truth’ (SOV) called ‘IO State’

• All services to sync data from SOV• Failure of SOV DOES NOT affect synchronization of data• Reload state on the fly at SOV and update ALL subscribed

services

Shared IO State



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So What Is IO State?



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What is IO State?

• Caches Communications Data • Synchronizes Architectural Props (distribute rules of

communication)• Handles API Authorizations (access for communication)• Api Docs Definitions (how to communicate)

I/O State is data directly related to a request/response, normally separated from functionality. Handles all data associated with communication and communication access

[email protected] Rubel


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What Does IO State Contain

•all the data contained in annotations act as rules associated with the URI endpoint (not URL or the FQDN)

•by containing all those rules in one file and caching that data, we can share it with the other architectural components (and abstract data from functionality)

• this enables us to change it on the fly and reload without having to restart any services allowing subscribed services to get changes pushed to them through web hooks

[email protected] Rubel


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I/O State : Communications Properties


Shared I/O State is ‘IO State’ data unbound from functionality so that it can be shared across architectural components. This is the approach used by distributed architectures.

Bound I/O State is ‘I/O State’ data bound to functionality which cannot be shared or synchronized with additional architectural components creating an ‘architectural cross cutting concern’. This is commonly found in centralized architectures.


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Shared I/O State


• DOESN’T bind to the application• DOESN’T bind to functionality• DOESN’T bind to a resource


Title TextWhat Does It Look Like?

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https://gist.github.com/orubel/7c4d0290c7b8896667a3


https://gist.github.com/orubel/7c4d0290c7b8896667a3

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•Api Blueprint•not role based• confuses I/O state with content/resource•duplicitous; lack of separation

•Swagger•not role based•based on annotations and thus not sharable in distributed architecture•duplicitous; lack of separation• redundant functionality for docs; does not make use of OPTIONS

•RAML•not role based• limited to CRUD-based REST of 4 calls per class•duplicitous; lack of separation


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• Dramatic Code reduction By Reducing Duplication• Automation of nearly all aspects of API• Nearly 0% downtime for changes to endpoint data and rules• New API Patterns (ie API Chaining (tm) )

What Does It Improve?



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Code Reduction (1 of 2)

Controller : Mixed Concerns (Duplication)@Secured(['ROLE_ADMIN', ‘ROLE_USER'])@RequestMapping(value="/create", method=RequestMethod.POST)@ResponseBodypublic ModelAndView createAddress(){

List authorities = springSecurityService.getPrincipal().getAuthorities() User user

if(authorities.contains(‘ROLE_ADMIN’)){if(params.id){

user = User.get(params.id.toLong())}else{

render(status:HttpServletResponse.SC_BAD_REQUEST)}}else if(authorities.contains(‘ROLE_USER’)){

user = User.get(principal.id)}Address address = new Address(params)

… address.user = user

…}Owen Rubel [email protected]


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Code Reduction (2 of 2)

Controller : Single Concernpublic ModelAndView createAddress(){ User user= (params.id)?User.get(params.id.toLong()): User.get(principal.id)

Address address = new Address(params) address.user = user

…}




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university of washington - the new api pattern

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