api days paris - when restful may be considered harmful

When RESTful may be considered harmful

Copyright Push Technology 2015

Ross Garrett @gssor

RESTful may be harmful, eh?

@gssor

4 @gssor


What do we mean by RESTful?

5 @gssor

Copyright Push Technology 20156 @gssor

When WebAPIs may be considered harmful


Ross Garrett @gssor


(Web) Apis can sting you

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What constitutes “harmful”?

• Poor end-user experience

• Insufficient scaling capacity

• Inappropriate implementation / usage

• HATEOAS?

• ???

@gssor


Poor User Experience

• This usually means slow / unreliable apps

• Often caused by the network

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#1 Data redundancy

{ uid : 1234567890, title : “Something”, db_key : “some_thing_item”, modified_date : “13-06-1991”, …}

@gssor


#1 Data redundancy

{ uid : 1234567890, title : “Something else”, db_key : “some_thing_item”, modified_date : “06-08-2015”, …}

It’s like the Internet is running with Debug turned on

@gssor


Insufficient scaling capability

• Growing from 1000 users to 1,000,000 users

• Should we simply add CPUs, NICs, etc?

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#2 Data delivery

Your clients

@gssor


#2 Data delivery

• How many requests do you service for data that hasn’t changed?

• Guess what? HTTP 304 is a thing

• Everything has a cost; only pay for what you need

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Inappropriate Implementation

• WebAPIs often mimic backend systems & operations

• If one system needs to notify another about an event - do they really need to know about each other?

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#3 Coupling

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#3 Coupling

• Message-driven distributed architectures prove to be much more robust and fault-tolerant.

• Producers and consumers are truly independent.

• Scalability is easier to achieve, and we can distribute messages to multiple systems at a time.

@gssor


The Internet…

• Unknown, uncontrolled resource

• It will let you down–Insufficient bandwidth–Inconsistent bandwidth–High latency–Loss of connectivity on a regular basis

• Be sympathetic to realities of the network

@gssor


The (mobile) Internet…

• HTTP & TCP slow-start are usually not a good match for constantly dropped connections

• Network interface kills battery

• Large responses + periodic polling = bad

@gssor


Recommendations?

• STOP polling!

• Remove data redundancies

• Avoid coupling

@gssor


Think Reactive

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http://www.reactivemanifesto.org


Responsiveness

• As far as users’ know - when application response time exceeds their expectations they assume the system is down

• Slow responses tie up resources on the called system and the calling application

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A responsive system is quick to react to all users — under blue skies and grey skies — in order to ensure a consistently positive user experience.


A Responsive System depends on one that is Resilient & Elastic

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Resilient

• A Resilient system can react to variable conditions and failures

• A resilient system keeps processing transactions, even when there are transient impulses, persistent stresses or component failures disrupting normal processing

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Resilient = Reliable


Elastic

• An elastic system can allocate / de-allocate resources for every individual component or client as demand varies

• Elasticity also requires non-blocking design

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Elastic is another word for Scalable


Message Driven

• A message-driven application may be event-driven, actor-based, or a combination of the two

• An event-driven system is based on events which are monitored by zero or more observers

–The caller doesn’t need to block waiting for a response from the invoked routine

• Event-driven applications are not focused on the call stack, but rather on triggering events

• Events may be encoded as messages that are placed in a queue that is monitored by zero or more observers

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The right fit

• WebAPIs have solved lots of problems, and provided lots of opportunity

• Reactive apps almost always demand streaming pub/sub messaging–Websockets!

• Conceptual simplicity != best performance


There is no “one size fits all” approach, think strategically and critically about your architecture

choices

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Questions?

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Thanks!

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api days paris - when restful may be considered harmful

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