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15s-patterns-of-modern-software-architecture.html
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---
layout: presentation
title: "Patterns of Modern Software Architecture"
permalink: /15s-patterns-of-modern-software-architecture/
---
layout: true
<footer>
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<a href="https://github.com/sikoried"><span class="username">sikoried</span></a>
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---
# Patterns of Modern Software Architecture
Korbinian Riedhammer
---
# Design = Architecture
_» The goal of software architecture is to minimize the human resources required to build and maintain the required system. «_
<div style="text-align: center; margin-top: 5%">
<a href="https://www.amazon.de/Clean-Architecture-Softwarearchitekturen-Praxis-Handbuch-Softwarestrukturierung/dp/395845724X/"><img style="width: 25%" src="{{site.baseurl}}/assets/clean-arch.jpg"></a>
<a href="https://www.amazon.de/Clean-Architecture-Craftsmans-Software-Structure/dp/0134494164/"><img style="width: 25%" src="{{site.baseurl}}/assets/clean-arch-de.jpg"></a>
</div>
.right[Robert C Martin (_Uncle Bob_). Clean Architecture]
???
Ein interessanter Nachmittag...
---
# Software Architecture Patterns
### Layered Architecture
### Service Oriented Architecture
### Event-driven Architecture
### Microkernel Architecture
### Microservices Architecture
.tiny[.right[_Most figures taken from Mark Richards: Software Architecture Patterns, Wiley, 2015._]]
---
# Layered Architecture
- components organized into horizontal layers
- layers represent a specific role within the application
.center[
<img style="width: 70%" src="{{site.baseurl}}/assets/sapr_0101.png">
]
---
# Layered Architecture (cont'd)
.center[
<img style="width: 60%" src="{{site.baseurl}}/assets/sapr_0102.png">
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- separation of concern among components; clear interfaces between layers
- components within a specific layer deal only with logic that pertains to that layer
- _layers of isolation_: no skipping of closed layers
???
Example: change GUI toolkit, retain logic and persistence
---
# Layered Architecture (cont'd)
.center[
<img style="width: 60%" src="{{site.baseurl}}/assets/sapr_0103.png">
]
- exception: if a layer would mostly forward requests
- example: service layer
- unreachable for presentation
- bypassable for business
---
# Layered Architecture: Example
.center[
<img style="width: 70%" src="{{site.baseurl}}/assets/sapr_0101.png">
]
???
DAO = database access object
---
# Layered Architecture
### Discussion
- solid general purpose pattern
- easy to implement and test
- watch out for _architecture sinkhole anti-pattern:_ requests flow through multiple layers with little to no logic performed
- tends to lead to monolithic designs
---
# Service Oriented Architecture (SOA)
.center[
<img style="width: 70%" src="{{site.baseurl}}/assets/ibm_soa.gif">
]
.right[Source: ibm.com]
---
# SOA: Principles
- **standardized service contract**: specified through one or more service description documents.
- **loose coupling**: services are designed as self-contained components, maintain relationships that minimize dependencies on other services
- **abstraction**: services are completely defined by service contracts and description documents; logic is hidden and encapsulated within their implementation
- **reusability**: designed as components, services can be reused more effectively, thus reducing development time
- **autonomy**: services have control over the logic they encapsulate
- **discoverability**: services are defined by description documents and listed in a service discovery
- **composability**: services are building blocks for applications
---
# SOA: Discussion
- autonomy helps for reusability, maintenance and deployment
- high (initial) investment to specify architecture
- high overhead: every service needs to do input parameter validation
---
# Event-driven Architecture
- highly decoupled, single-purpose event processing components
- asynchronous event processing
- two main topologies
- mediator
- broker
---
# Event-driven Architecture: Mediator
.center[
<img style="width: 70%" src="{{site.baseurl}}/assets/sapr_0201.png">
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---
# Event-driven Architecture: Mediator Example
.center[
<img style="width: 70%" src="{{site.baseurl}}/assets/sapr_0202.png">
]
---
# Event-driven Architecture: Broker
.center[
<img style="width: 70%" src="{{site.baseurl}}/assets/sapr_0203.png">
]
---
# Event-driven Architecture: Broker Example
.center[
<img style="width: 55%" src="{{site.baseurl}}/assets/sapr_0204.png">
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---
# Event-driven Architecture
### Discussion
- excellent scalability and unit-testing
- asynchronicity brings complexity, eg.
- remote process availability
- lack of responsiveness
- broker reconnection logic in the event of a broker or mediator failure
- lack of atomic transactions for business processes
- requires discipline regarding event format (eg. JSON)
- end-to-end testing hard
---
# Event-driven Architecture
### Toolkits
- Apacha Kafka: <https://kafka.apache.org/>
- Otto: application-based event bus <https://square.github.io/otto/>
- Reactive Programming: <https://github.com/ReactiveX/RxJava>
---
# Microkernel Architecture
### Or: Plugin Architecture
.center[
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]
---
# Microkernel Architecture
- make your product flexible in terms of features and extensibility
- core has minimum functionality, foremost plugin handling (registry)
- keep communication/dependency among plugins to minimum
- plugin-core-connection
- OSGi (open service gateway initiative)
- messaging
- web services
- direct point-to-point binding (i.e., object instantiation)
- example: photoshop :-)
---
# Microservices Architecture
An alternative to monolithic applications.
- central concept: separately deployed units
- easier deployment through an effective and streamlined delivery pipeline
- increased scalability
- high degree of application and component decoupling
- service components that act in bounded context
- the hard part: getting the granularity right
See <https://www.bmc.com/blogs/microservices-vs-soa-whats-difference/> for a good differentiation to service oriented architecture (SOA).
---
# Microservices Architecture (cont'd)
### Variant: API REST-based
.center[
<img style="width: 65%" src="{{site.baseurl}}/assets/sapr_0402.png">
]
---
# Microservices Architecture (cont'd)
### Variant: Application REST-based
.center[
<img style="width: 65%" src="{{site.baseurl}}/assets/sapr_0403.png">
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- similar to API REST-based, but requests from browser or fat-client
---
# Microservices Architecture (cont'd)
### Variant: Centralized Messaging System
.center[
<img style="width: 45%" src="{{site.baseurl}}/assets/sapr_0404.png">
]
- typical for larger-scale application
- allows for advanced queuing mechanisms, asynchronous messaging, monitoring, error handling, and better overall load balancing and scalability
---
# Microservices Architecture
### Discussion
- vital to get the granularity right
- too fine: scaling or communication hell
- too coarse: no benefit
- inter-service communication should use database instead of tight coupling
- excellent testing capabilities
- excellent deployment: "hot-swap" instances until no old instance left
- ideal for containerization → simple orchestration!
---
# Microservices vs. SOA
- SOA requires all participants to know the common communication mechanism
- In SOA, services (typically) share data storage; microservices maintain their own
- SOA may entail microservices