Bounded Contexts, Microservices, and Everything In Between

Bounded Contexts, Microservices, and Everything In Between

“95% of the words are spent extolling the benefits of ‘modularity’ and that little, if anything, is said about how to achieve it” - Glenford J. Myers, 1978. This quote is 40 years old. Today, 4 decades later, nothing has changed except terminology. Time to fix this.

I want to talk about the various strategies of decomposing systems into modular components. We will learn what exactly Bounded Contexts and Microservices are. See how and why they differ. Analyze what happens between services - how data flows, and how this flow can be optimized. Ultimately, we will explore different decomposition strategies and heuristics for designing modular systems. Systems that aren’t driven by ever-changing fads, but by your business needs.

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Vladik Khononov

October 18, 2018
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Transcript

  1. MICROSERVICES BOUNDED CONTEXTS AND EVERYTHING IN BETWEEN vladikk

  2. @vladikk vladikk.com

  3. ”95% of the words are spent extolling the benefits of

    “modularity” and that little, if anything, is said about how to achieve it” Glenford J. Myers Composite / Structured Design, 1974
  4. “MICROSERVICES FTW!!!!!!!!1” Me @ Internovus

  5. “MICROSERVICES FTW!!!!!!!!1” Me @ Internovus

  6. None
  7. ”95% of the words are spent extolling the benefits of

    “modularity” and that little, if anything, is said about how to achieve it” Glenford J. Myers Composite / Structured Design, 1974
  8. None
  9. None
  10. Decomposi/on Strategies Microservices Design Heuris/cs

  11. vladikk NAXEX / INTERNOVUS 01 BUSINESS DOMAIN

  12. Your Product Marketing
 Strategy Creatives Campaigns Sales
 Agents Optimization Profits

  13. vladikk DECOMPOSITION 02 STRATEGIES

  14. Bounded Contexts

  15. None
  16. Business Domain Expert Software Developer ??? !!! Ubiquitous Language

  17. Campaigns Sales
 Agents Your Product Marketing
 Strategy Creatives Optimization Profits

  18. Campaigns Sales
 Agents Your Product Marketing
 Strategy Creatives Optimization Profits

  19. Sales Agent Campaign Manager ??? !!! LEAD?

  20. Conflicting models Different contexts Dividing the language/model Bounded Context

  21. MarkeCng Sales Lead Lead Funnel Campaign Placement Landing Page Agency

    Insertion Order Message Campaign Proposition Desk Conversion Contact CDR Bounded Contexts
  22. MarkeCng Service Sales Service DecomposiCon Strategy #1: Bounded Contexts

  23. MarkeCng

  24. MarkeCng Creative Catalog Contracts Billing Campaign Management Identity & Access

    Ads Optimization
  25. MarkeCng Sales Creative Catalog Contracts Billing Campaign Management Identity &

    Access Ads Optimization
  26. MarkeCng Sales Commissions Desks Sales
 Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ads Optimization Identity & Access
  27. Business (Sub)Domains

  28. Business Domain: Customer Acquisi/on Bounded Context: Marke/ng Bounded Context: Sales

    Subdomain: Crea/ve Catalog Subdomain: Campaigns Mngmt Subdomain: Ads Op/miza/on Subdomain: Contracts Mngmt Subdomain: CRM Subdomain: Sales Op/miza/on Subdomain: Commissions Subdomain: Desks Mngmt
  29. DecomposiCon Strategy #2: Subomains Campaign Management Service Content Catalog Service

    Desks Management Service CRM Service Users Service Billing Service
  30. Business EnCCes and Processes

  31. MarkeCng Creative Catalog Contracts Billing Campaign Management Identity & Access

    Optimization
  32. MarkeCng Creative Catalog Contracts Billing Campaign Management Identity & Access

    Optimization Campaign Management Campaign Placement Funnel Banner Landing Page Website Zone Asset Publisher Target Market
  33. DecomposiCon Strategy #3: EnCCes Website Asset Target Market Broker Distribu/on

    Customer
  34. DecomposiCon Strategies Bounded Contexts Subdomains Business Entities and Processes

  35. SHOW ME THE MICROSERVICES!

  36. Bounded Contexts == Microservices ?

  37. Sales Agent Campaign Manager ??? !!! LEAD?

  38. MarkeCng Sales Lead Lead Funnel Campaign Placement Landing Page Agency

    Insertion Order Message Campaign Proposition Desk Conversion Contact CDR
  39. MarkeCng Sales Lead Lead Funnel Campaign Placement Landing Page Agency

    Insertion Order Message Campaign Proposition Desk Conversion Contact CDR
  40. MarkeCng Sales Lead Lead Funnel Campaign Placement Landing Page Agency

    Insertion Order Message Campaign Proposition Desk Conversion Contact CDR
  41. MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts

    Billing Campaign Management Identity & Access Optimization Identity & Access Lead Lead
  42. MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts

    Billing Campaign Management Identity & Access Optimization Identity & Access Lead Lead
  43. MarkeCng Creative Catalog Campaign Management Optimization Lead Sales Commissions Optimization

    CRM Lead Desks Telephony Support Contracts Billing Identity & Access
  44. Bounded Contexts Decomposi/on #1 Bounded Contexts Decomposi/on #2 Bounded Contexts

    Decomposi/on #3
  45. Bounded Context Consistency boundary of the language / model Define

    the biggest valid monoliths Required decomposition boundary
  46. Bounded Contexts == Microservices? No

  47. Campaign Management Campaign Placement Funnel Banner Landing Page Website Zone

    Asset Publisher Target Market Campaign Website Placement Funnel MarkeCng Creative Catalog Contracts Billing Campaign Management Identity & Access Optimization Bounded Contexts? No Subdomains? EnCCes?
  48. Campaign Management Campaign Placement Funnel Banner Landing Page Website Zone

    Asset Publisher Target Market Campaign Website Placement Funnel MarkeCng Creative Catalog Contracts Billing Campaign Management Identity & Access Optimization Bounded Contexts? No Subdomains? EnCCes?
  49. vladikk MICROSERVICES 03

  50. Service “A service is a unit of functionality exposed to

    the world” - Juval Lowy “A mechanism to enable access to one or more capabilities, where the access is provided using a prescribed interface” - OASIS
  51. “A service is a unit of functionality exposed to the

    world” - Juval Lowy “A mechanism to enable access to one or more capabilities, where the access is provided using a prescribed interface” - OASIS Service
  52. Service Interface “Any mechanism for getting data in or out

    of the service” - Randy Shoup
  53. Service Interface Synchronous: • Request / Réponse • Bulk ETL

  54. Service Interface Asynchronous: • Producing events • Consuming events Synchronous:

    • Request / Réponse • Bulk ETL
  55. Service Interface “Any mechanism for getting data in or out

    of the service” - Randy Shoup
  56. Service Interface

  57. Services ➜ Microservice

  58. A microservice is a service with a micro interface

  59. A microservice is a service with a micro interface

  60. Microservice = Microinterface Reducing coupling between services Limits reasons for

    change Easier to understand Better fault isolation More autonomy between services
  61. Microservice & Databases Microservices should own its database No external

    access Access through Microservice’s API only Database = infinite interface!
  62. But!

  63. 1 Method = Perfect Microservice !!??

  64. None
  65. None
  66. None
  67. None
  68. None
  69. None
  70. STAFF ONLY STAFF ONLY

  71. The threshold upon which a system can be decomposed into

    microservices is defined by the use cases of the system that the microservices are a part of.
  72. Monolith Microservices Cost of Change

  73. Monolith Microservices Distributed
 Monolith Cost of Change

  74. Big Ball Of Mud Bounded Contexts Microservices Distributed Big Ball

    Of Mud Avg. Service Size
  75. Campaign Management Campaign Placement Funnel Banner Landing Page Website Zone

    Asset Publisher Target Market Campaign Website Placement Funnel Subdomains? EnCCes?
  76. None
  77. None
  78. ”Global complexity … the complexity of the overall structure of

    a program or system. I.e., the degree of association or interdependence among the major pieces of a program” Glenford J. Myers Composite / Structured Design, 1974
  79. ”Global complexity … the complexity of the overall structure of

    a program or system. I.e., the degree of association or interdependence among the major pieces of a program” Glenford J. Myers Composite / Structured Design, 1974
  80. ”Global complexity … the complexity of the overall structure of

    a program or system. I.e., the degree of association or interdependence among the major pieces of a program” Glenford J. Myers Composite / Structured Design, 1974
  81. When you design a system…, then if the features can

    be broken into … loosely bound groups of rela>vely closely bound features, then that division is a good thing to be made a part of the design. This is just good engineering. Tim Berners-Lee Principles of design, 1998
  82. Services + Good Engineering = Microservices

  83. Its is not only necessary to make sure your own

    system is designed to be made of modular parts. It is also necessary to realize that your own system … should always be designed to be a part of another larger system. Tim Berners-Lee Principles of design, 1998
  84. A major part of this paper will be concerned with

    the ques>on of how good modularity can be achieved, that is, how modules can be chosen so as to minimize the connec5ons between them. Barbara Liskov A design methodology for reliable soIware systems, 1972
  85. A microservice is a service with a micro interface. The

    threshold upon which a system can be decomposed into microservices is defined by the use cases of the system that the microservices are a part of.
  86. A microservice is a service with a micro interface. The

    threshold upon which the system can be decomposed is defined by the use cases of the system that the microservices are a part of. …how to evaluate?
  87. vladikk DESIGN 04 HEURISTICS

  88. HeurisCc #1: Decompose to Bounded Contexts Do not implement conflicting

    models in the same service. 
 Always decompose to Bounded Contexts.
  89. HeurisCc #2: Don’t ”First Law of Distributed Object Design: 


    “Don’t distribute your objects” MarCn Fowler
  90. HeurisCc #2: Don’t Benefits Addi/onal
 Complexity

  91. Monolith: System design that undermines delivery of functional or non-functional

    requirements
  92. HeurisCc #2: Don’t Benefits Addi/onal
 Complexity

  93. HeurisCc #2: Don’t Benefits Addi/onal Complexity

  94. Core Supporting Generic

  95. Generic Subdomains No competitive advantage Everybody is implementing in the

    same way Complex business logic
  96. MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts

    Billing Campaign Management Identity & Access Optimization Identity & Access Generic
  97. MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts

    Billing Campaign Management Identity & Access Optimization Identity & Access Generic
  98. MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts

    Billing Campaign Management Identity & Access Optimization Identity & Access Generic
  99. MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts

    Billing Campaign Management Identity & Access Optimization Identity & Access Generic
  100. MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts

    Billing Campaign Management Identity & Access Optimization Identity & Access Generic
  101. MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts

    Billing Campaign Management Identity & Access Optimization Identity & Access Generic
  102. MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts

    Billing Campaign Management Identity & Access Optimization Identity & Access Generic
  103. MarkeCng Sales Commissions Desks Optimization CRM Telephony Creative Catalog Contracts

    Billing Campaign Management Identity & Access Optimization Identity & Access Generic
  104. HeurisCc #3: Buy/Adopt Generic Subdomains Your System 3rd party product

  105. HeurisCc #3: Buy/Adopt Generic Subdomains Your System 3rd party product

    An/-Corrup/on Layer
  106. Core Subdomains Inventing something new Optimizing existing paractices Competitive advantage

    Complex business logic Change often
  107. MarkeCng Sales Commissions Desks Sales
 Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core
  108. MarkeCng Sales Commissions Desks Sales
 Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core
  109. MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core
  110. MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core
  111. MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core
  112. MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core
  113. Core Subdomains Inventing something new Optimizing existing paractices Competitive advantage

    Complex business logic Change often
  114. HeurisCc #4: Core Subdomains - Don’t Rush Adhere to subdomain’s

    boundaries. Decompose further only when you acquire domain knowledge.
  115. SupporCng Subdomains No competitive advantage Support the Core Subdomains Can’t

    be bought / adopted Simple business logic
  116. MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core Supporting
  117. MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core Supporting
  118. MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core Supporting
  119. MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core Supporting
  120. MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core Supporting
  121. MarkeCng Sales Commissions Desks Sales Optimization CRM Telephony Creative Catalog

    Contracts Billing Campaign Management Identity & Access Ad Optimization Identity & Access Generic Core Supporting
  122. SupporCng Subdomains No competitive advantage Support the Core Subdomains Can’t

    be bought / adopted Simple business logic
  123. HeurisCc #5: SupporCng Subdomains - Safe Safe to decompose beyond

    the subdomain’s boundaries.
  124. Core Supporting Generic

  125. HeurisCc #6: Evaluate Consistency Requirements Method A Method B

  126. HeurisCc #6: Evaluate Consistency Requirements Concurrency control? - Same service

    Method A Method B 
 Service A
  127. HeurisCc #6: Evaluate Consistency Requirements Read last write? - Two

    services, synchronous communication 
 Service A Method A 
 Service B Method B Sync call
  128. HeurisCc #6: Evaluate Consistency Requirements Eventual consistency? - Two services,

    asynchronous communication 
 Service A Method A 
 Service B Method B Asynchronous Communication
  129. HeurisCc #6: Evaluate Consistency Requirements Concurrency control? - Same service

    Read last write? - Two services, sync communication Eventual consistency? - Two services, async communication
  130. 
 Service A Method A 
 Service B Method B

    Asynchronous Communication
  131. HeurisCc #7: Public / Private Events Service Event Type 1

    Event Type 2 Event Type 3 Event Type 4 Event Type 5 Event Type 6 Event Type 1000 …
  132. HeurisCc #7: Public / Private Events Service Event Type 1

    Event Type 2 Event Type 3 Event Type 4 Event Type 5 Event Type 6 Event Type 1000 … Private event types (Implementation details) }
  133. HeurisCc #7: Public / Private Events Service Event Type 1

    Event Type 2 Event Type 3 Event Type 4 Event Type 5 Event Type 6 Event Type 1000 … Private event types (Implementation details) }Public event types (Public interface) }
  134. Service HeurisCc #7: Public / Private Events

  135. Service EmailChanged PhoneNumberChanged AddressChanged HeurisCc #7: Public / Private Events

  136. Service EmailChanged PhoneNumberChanged AddressChanged HeurisCc #7: Public / Private Events

  137. Service EmailChanged PhoneNumberChanged AddressChanged ContactDetailsChanged HeurisCc #7: Public / Private

    Events
  138. Service EmailChanged PhoneNumberChanged AddressChanged ContactDetailsChanged Private event types (Implementation details)

    } Public event type (Public interface) } HeurisCc #7: Public / Private Events
  139. HeurisCc #7: Public / Private Events Events?

  140. HeurisCc #7: Public / Private Events Events? Domain Events

  141. HeurisCc #7: Public / Private Events Events? Domain Events State

    Change
 Events
  142. HeurisCc #7: Public / Private Events Events? Domain Events State

    Change
 Events Private Public
  143. HeurisCc #8: Make Events Explicit Eliminate ambiguity

  144. HeurisCc #8: Make Events Explicit Service AgentAssignedToLead

  145. HeurisCc #8: Make Events Explicit Service AgentAssignedToLead AgentAssignedToLead AgentAssignedToLead

  146. HeurisCc #8: Make Events Explicit Service AgentAssignedToLead AgentUnassignedToLead AgentAssignedToLead

  147. HeurisCc #8: Make Events Explicit Service AgentAssignedToLead AgentUnassignedToLead AgentAssignedToLead

  148. HeurisCc #9: Evaluate Reasons for Change Service A Service B

  149. Same reasons for change? Same rate of change? Can be

    decoupled? Should be the same service? HeurisCc #9: Evaluate Reasons for Change
  150. None
  151. HeurisCc #10: Evaluate Services’ “Doors”

  152. HeurisCc #10: Evaluate Services’ “Doors” STAFF ONLY STAFF ONLY

  153. HeurisCc #10: Evaluate Services’ “Doors” STAFF ONLY STAFF ONLY

  154. vladikk WRAP UP 05

  155. 1. A service is a unit of func/onality exposed to

    the world through its public interface. 2. A microservice is a service with micro interface 3. The “micro-interface” is rela/ve to the use cases of the system that the service is a part of
  156. Heuris/c #1: Always decompose to Bounded Contexts Heuris/c #2: Don’t

    go further, unless you have to Heuris/c #3: Buy/adopt generic subdomains Heuris/c #4: Core subdomains - don’t rush Heuris/c #5: Suppor/ng subdomains can be decomposed early
  157. Heuris/c #6: Evaluate Consistency Requirements Heuris/c #7: Private / Public

    Events Heuris/c #8: Explicitly Define Events Heuris/c #9: Evaluate Reasons for Change Heuris/c #10: Evaluate Services’ “Doors”
  158. Big Ball Of Mud Bounded Contexts Microservices Distributed Big Ball

    Of Mud Avg. Service Size
  159. Bibliography 1. A Design Methodology for Reliable Soeware Systems, Barbara

    Liskov 2. Composite/Structured Design, Glenford Myers 3. Domain-Driven Design: Tackling Complexity in the Heart of Soeware, Eric Evans 4. Emerging Boundaries, Mathias Veraes 5. Implemen/ng Domain-Driven Design, Vaughn Vernon 6. Enterprise Integra/on Paherns, Gregory Hohpe, at al 7. Long Sad Story of Microservices, Greg Young 8. Managing Data in Microservices, Randy Shoup 9. Microservices, At Last Some Boundaries, Eric Evans 10. On the Criteria to be Used in Decomposing Systems Into Modules, David Parnas 11. Paherns of Enterprise Applica/on Architecture, Mar/n Fowler, at al 12. Principles of Design, Tim Berners-Lee 13. Programming WCF Services, Juval Lowy 14. What Every Programmer Should Know About Object Oriented Design, Melir Page-Jones
  160. QUESTIONS? @vladikk vladikk.com

  161. THANK YOU! @vladikk vladikk.com