In deze samenvatting krijg je uitleg over alle dia's van het vak systeemontwerp aan de UGent. De honderden dia's worden zo beperkt tot een honderdtal pagina's. Tevens is alles in het Nederlands
Hoofdstuk 0: Introduction .............................................................................................................................. 6
Systeemcomponenten ........................................................................................................................................ 7
Systeemontwerp in bedrijven en deployen van een systeem ............................................................................. 7
Systeemarchitectuur .......................................................................................................................................... 8
Systeemrequirements......................................................................................................................................... 8
4 + 1 view model van softwarearchitectuur ....................................................................................................... 8
Reactive Manifesto .......................................................................................................................................... 11
Hoofdstuk 1: Microservices .......................................................................................................................... 13
Architectural style ............................................................................................................................................ 13
Wat is architecturale stijl ................................................................................................................................. 13
4 Architecturale stijlen ..................................................................................................................................... 13
Microservices ................................................................................................................................................... 16
Wat is een service ............................................................................................................................................ 16
Wat is een microservice ................................................................................................................................... 16
What is loosely coupled? .................................................................................................................................. 17
Nadelen/Challenges van het MicroService pattern .......................................................................................... 17
Decompositie.................................................................................................................................................... 18
Stap 1: identificeren en begrijpen van systeemoperaties................................................................................. 18
Stap 2: Identificeren van services door business capabilities ........................................................................... 19
Stap 3: Definiëren van service API’s en collaborations ..................................................................................... 20
Finaliseren van de services ............................................................................................................................... 21
Problemen bij decompositie ............................................................................................................................. 21
Interactiestijlen tussen micro-services ............................................................................................................. 22
Interactie is een logisch en technisch probleem ............................................................................................... 22
Interactiestijlen ................................................................................................................................................ 22
Synchrone communicatie: gRPC ....................................................................................................................... 24
Handling partial failure .................................................................................................................................... 24
Bulkhead: limiet zetten op het aantal uitgaande requests .............................................................................. 25
Circuit breaker .................................................................................................................................................. 25
Fallback strategy to recover from failing call ................................................................................................... 25
Asynchrone communicatie: Messaging ............................................................................................................ 25
Messaging supports all interaction styles ........................................................................................................ 26
Specification for messaging-based service API ................................................................................................ 26
1
, Message broker technologieën ........................................................................................................................ 27
Design issues: competing consumers ............................................................................................................... 27
Hoe lost Kafka die problemen op? ................................................................................................................... 27
Kafka at work: voorbeeld MMOG .................................................................................................................... 28
Design issues: handling duplicate messages .................................................................................................... 29
Synchrone interactie reduceert beschikbaarheid vd applicatie ........................................................................ 30
Interactie is orthogonaal (niet gelijk aan) de gebruike communicatie............................................................. 30
Eliminating Synchronous interaction................................................................................................................ 31
Saga’s ............................................................................................................................................................... 32
Transactiegaranties in een monoliet (monolithic system) ............................................................................... 32
Distributed transactions: 2PC (2 phase commit) (bij microservices) ................................................................ 32
Saga: sequentie van lokale transacties ............................................................................................................ 33
Transactionele messaging ................................................................................................................................ 33
Compensating transactions ............................................................................................................................. 33
Voorbeeld: rejecting an order .......................................................................................................................... 34
Concurrent Saga’s ............................................................................................................................................ 34
Saga coordination: hoe wordt de saga uitgevoerd? ........................................................................................ 34
State Machine model ....................................................................................................................................... 35
Business logica van een enkele microservice ................................................................................................... 36
Business logic organization .............................................................................................................................. 36
Building blocks for a good domain model ........................................................................................................ 37
= Een klasse: heeft ............................................................................................................................................ 37
Putting everything in place .............................................................................................................................. 39
Example: restaurant order management ......................................................................................................... 39
Queries in a microservice architecture ............................................................................................................. 40
The API composition pattern ............................................................................................................................ 40
Design issue: wie speelt de rol van API composer? .......................................................................................... 40
Moeilijkheden bij queries naar 1 service .......................................................................................................... 41
Command-Query responsibility segregation: oplossing voor moeilijkheden ................................................... 41
Hoofdstuk 2: Deployment and orchestratie .................................................................................................. 43
From the bottom to the top: Development naar productie ............................................................................. 43
Making your service production ready ............................................................................................................. 44
Configureerbare services .................................................................................................................................. 44
Push-based externalized configuration ............................................................................................................ 44
Pull-based externalized configuration .............................................................................................................. 44
Observable services .......................................................................................................................................... 44
Log aggregation ............................................................................................................................................... 45
Distributed Tracing ........................................................................................................................................... 45
2
,Audit logging .................................................................................................................................................... 45
Application metrics .......................................................................................................................................... 46
Containers als een unit voor deployment ......................................................................................................... 46
Probleemstatement: development to operations ............................................................................................ 46
Virtual machine images als deployable artifacts ............................................................................................. 46
Host virtualisatie: VM’s en containers ............................................................................................................. 47
Linux containers technology stack ................................................................................................................... 47
Functies van Linux Kernel: Linux Control Groups (CGROUPS) ........................................................................... 47
Functie van de Linux Kernel: Linux namespaces ............................................................................................... 48
Functie van Linux Kernel: changing root .......................................................................................................... 48
Functie van Linux Kernel: Secure containers .................................................................................................... 48
Wat is Docker? ................................................................................................................................................. 48
Docker vs Linux containers ............................................................................................................................... 49
Docker architectuur .......................................................................................................................................... 49
Building images from Dockerfiles ..................................................................................................................... 49
Images layers ................................................................................................................................................... 50
Container vs image........................................................................................................................................... 50
Building an image ............................................................................................................................................ 50
Union file system .............................................................................................................................................. 50
Container Orchestration................................................................................................................................... 51
Wat doet een Orchestration framework? ........................................................................................................ 51
Kubernetes architectuur ................................................................................................................................... 51
Kubernetes concepten: PODS en deployment objecten ................................................................................... 52
Multicontainer pods ......................................................................................................................................... 52
Service discovery: the need of a service registry .............................................................................................. 52
Hoe gaan clients de services in het registry vinden? ........................................................................................ 53
Servcie Discovery in Kubernetes? ..................................................................................................................... 53
Load balancer ................................................................................................................................................... 53
Rolling updates: zero-downtime ...................................................................................................................... 54
Andere deployment operaties met een load balancer ..................................................................................... 54
Dimensions of cloud computing ....................................................................................................................... 55
Essentiële karakterisitieken .............................................................................................................................. 55
Stakeholders (service models) .......................................................................................................................... 55
De rol van de cloud provider ............................................................................................................................ 55
Multi-tenant homogeneous pooled resources ................................................................................................. 56
Cloud service models: X as a service (fill in the X) ............................................................................................ 56
Deployment models (nieuwe pijl, de pijl omhoog) ........................................................................................... 58
Elastic Auto-scaling .......................................................................................................................................... 59
3
, Cloud user objectives........................................................................................................................................ 59
Statisch vs elastisch schalen ............................................................................................................................. 59
Verschillende soorten workload ....................................................................................................................... 60
Types of scaling ................................................................................................................................................ 60
Verticaal schalen .............................................................................................................................................. 61
Horizontaal schalen.......................................................................................................................................... 61
Autoscaling....................................................................................................................................................... 61
Case study; auto-scaling in Amazon EC2 .......................................................................................................... 62
Standy pooling ................................................................................................................................................. 62
Scaling guidelines ............................................................................................................................................. 63
Multisite deployment ....................................................................................................................................... 63
Two stage load balancing ................................................................................................................................ 63
Example: Google Compute Engine ................................................................................................................... 64
Hoofdstuk 3: Data intensieve systemen: Deel 1 ............................................................................................... 66
Challenges of modern data .............................................................................................................................. 66
Data-intensieve systemen ................................................................................................................................ 66
Datamodellen................................................................................................................................................... 66
NoSQL ............................................................................................................................................................... 68
Data storage and retrieval ............................................................................................................................... 69
Twee soorten storage engines ......................................................................................................................... 69
Hoe storage engines beoordelen? .................................................................................................................... 69
B-tree index for page-based storage ................................................................................................................ 70
Log-structured storage engines ....................................................................................................................... 70
Betrouwbaarheid van een DB .......................................................................................................................... 71
Comparing B-trees to LSM-trees ...................................................................................................................... 71
Ster schema voor analyse................................................................................................................................. 72
Relationele data opgeslagen per kolom, niet per rij ........................................................................................ 72
Distributed data ............................................................................................................................................... 73
Waarom data distribueren? ............................................................................................................................. 73
Patterns voor datadistributie ........................................................................................................................... 73
Distribute data: replicatie ................................................................................................................................ 74
Replicating changes: leader-folower model ..................................................................................................... 74
Replicating changes: leaderless model ............................................................................................................ 75
Quorums for reading and writing..................................................................................................................... 77
Quorum consistency ......................................................................................................................................... 78
Sloppy Quorums ............................................................................................................................................... 78
Distributed data: partitioning/sharding ........................................................................................................... 79
Waarom partitioneren? ................................................................................................................................... 79
4
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