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.

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
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
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
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 !!??
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?
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
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