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Of Microservices And Monoliths
Stefan Priebsch, The PHP Consulting Company
Consultant
Consultant
Coach
Consultant
Coach
Author
Consultant
Coach
Author
University Lecturer
Consultant
Coach
Author
University Lecturer
Scalability Expert
Working on "Event Sourcing Explained"
Visit https://event-sourcing-explained.com/
Monolith = Antipattern?
In most cases, monoliths are the status quo.
The Distributed Monolith
The Distributed Monolith
Does a change to one microservice require changes to or deployments of other microservices?
Are your microservices overly chatty?
Do several microservices share a datastore?
Do my services scale dynamically?
https://blog.newrelic.com/engineering/distributed-monolith-vs-microservices/
The Distributed Monolith
Implementing one business feature requires touching multiple microservices
~ 30 Mio lines of PHP code
Interesting performance problems
HipHop: Cross-compile PHP to C++
50% less CPU
1.5 GB binaries
Deployment?
Local testing?
Compiler in production, interpreter in development
HHVM: JIT compiler for PHP
— Adam Bien, "Enterprise Architekturen"
⟫ ⟪Every architecture's number one enemy is the compiler.
Compile into monolith?
Single process vs. network latency
Deployment?
Scripting languages
Deploy source code into production
Load code dynamically
Request/Response
Static object graph
Short lifetime
External state
Serverless?
Boundaries
Boundaries
Decomposition
Boundaries
Decomposition
Coupling
Tight coupling starts in the business
Quote
Order
Invoice
Order::fromQuote(...)
Invoice::fromOrder(...)
Decouple
Abstract
...
$twitter= new TwitterAPIExchange($settings);
...
$twitter->buildOauth($url, $requestMethod) ->setPostfields($postfields) ->performRequest();
Still very technical!
Domain view?
$twitter->tweet(...);
$microblog->publishMessage(...);
"Abstractions should not depend upon details"
$remoteService->authenticate($credentials);$remoteService->sendRequest(...);
...
public function publish($message){ $this->microblog->authenticate(...); $this->microblog->sendRequest(...);}
...
— John V. Guttag
⟫
⟪
The essence of abstractions is preserving information that isrelevant in a given context, and forgetting information that is
irrelevant in that context.
Details:
API requires authentication
Resources have URLs
...
REST is an implementation detail
of the client-server communication
Why REST?
public function publishMessage($message){ ... $this->authenticate(...); $this->sendPostRequest(...); ...}
public function publishMessage($message){ ... $this->sendJsonRpc(...); ...}
public function publishMessage($message){ ... $this->sendXmlRpc(...); ...}
public function publishMessage($message){ ... $this->sendSoapRequest(...); ...}
Integrate client and server in one process?
Develop distributed, deploy monolithic
Facade API
The API is an interface (as in class implements interface)
Facade API
Tell to do something
Ask a question
Facade API
Send a command (e.g. "publish message")
Run a query (e.g. "show list of friends")
CQRS
CQRS
Use a REST API for queries
Use an RPC-style API for commands
Separate side e�ects
Separate side e�ects
Record the decision to publish a message. Deal with the side e�ects later.
Need-to-know principle
Push Model
More async, less sync
No temporal coupling
Vertical vs. horizontal separation
Self-contained systems
Self-contained systems
Each SCS is an autonomous web application.
Each SCS is owned by one team.
Communication with other SCSs or 3rd party systems is asynchronous wherever possible.
An SCS can have an optional service API.
Each SCS must include data and logic.
An SCS should make its features usable to end-users by its own UI.
To avoid tight coupling an SCS should share no business code with other SCSs.
Shared infrastructure should be reduced to increase availability and decrease coupling.
Slides: https://talks.thephp.cc
https://thephp.cc stefan@thephp.cc @spriebsch
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