Applying Microservices Patterns to a Modular Monolith

Dealing with legacy monoliths can be challenging due to accumulated technical debt. When faced with this situation, we usually start looking at different strategies to solve this, like microservices, engines, and modularization, just to name a few.

When choosing to follow a modular approach, I explored applying microservices patterns to our modular monolith. In this talk, I’ll share my experience in adopting this approach, focusing on ensuring data consistency and distributed transactions, as well as the pitfalls and insights I discovered along the way.

Transcript

1. Guillermo Aguirre - April 2023 Applying Microservices Patterns to a Modular Monolith
2. Guillermo Aguirre - RailsConf 2023 Welcome!
3. Guillermo Aguirre - RailsConf 2023 About me @guillermoap @guillermoap_ @guillermo.aguirre Guillermo Aguirre /gee-SHER-moh ah-GHEE-rreh/
4. Guillermo Aguirre - RailsConf 2023 Where I work
5. Guillermo Aguirre - RailsConf 2023 Agenda
6. Guillermo Aguirre - RailsConf 2023 Agenda My journey
7. Guillermo Aguirre - RailsConf 2023 Agenda My journey Our Domain
8. Guillermo Aguirre - RailsConf 2023 Agenda My journey Our Domain Pattern explanations
9. Guillermo Aguirre - RailsConf 2023 Agenda My journey Our Domain Pattern explanations Example App
10. Guillermo Aguirre - RailsConf 2023 Agenda My journey Our Domain Pattern explanations Example App Demo
11. Applying Microservices Patterns to a Modular Monolith My journey
12. Applying Microservices Patterns to a Modular Monolith My journey MVPs
13. Applying Microservices Patterns to a Modular Monolith My journey MVPs Big monoliths
14. Applying Microservices Patterns to a Modular Monolith My journey MVPs Big monoliths Microservices
15. Applying Microservices Patterns to a Modular Monolith Monoliths The good
16. Applying Microservices Patterns to a Modular Monolith Monoliths Widely used The good
17. Applying Microservices Patterns to a Modular Monolith Monoliths Nothing wrong with them Widely used The good
18. Applying Microservices Patterns to a Modular Monolith Monoliths My experience
19. Applying Microservices Patterns to a Modular Monolith 1 | class User < ApplicationRecord ... | ... 2473 | end Monoliths My experience
20. Applying Microservices Patterns to a Modular Monolith Monoliths The bad
21. Applying Microservices Patterns to a Modular Monolith Long deployment times Monoliths The bad
22. Applying Microservices Patterns to a Modular Monolith Long deployment times Monoliths The bad Tightly coupled code
23. Applying Microservices Patterns to a Modular Monolith Long deployment times Monoliths The bad Tightly coupled code => Harder to maintain & extend
24. Applying Microservices Patterns to a Modular Monolith Microservices The good
25. Applying Microservices Patterns to a Modular Monolith Smaller cohesive teams Microservices The good
26. Applying Microservices Patterns to a Modular Monolith Smaller cohesive teams Distributed Microservices The good
27. Applying Microservices Patterns to a Modular Monolith Microservices My experience
28. Applying Microservices Patterns to a Modular Monolith Data inconsistencies Microservices My experience
29. Applying Microservices Patterns to a Modular Monolith Data inconsistencies Hot- f ix issues in production Microservices My experience
30. Applying Microservices Patterns to a Modular Monolith Microservices The bad
31. Applying Microservices Patterns to a Modular Monolith Signi f icantly higher infrastructure complexity Microservices The bad
32. Applying Microservices Patterns to a Modular Monolith Signi f icantly higher infrastructure complexity Distributed mess Microservices The bad
33. Applying Microservices Patterns to a Modular Monolith Modularization
34. Applying Microservices Patterns to a Modular Monolith Modularization
35. Applying Microservices Patterns to a Modular Monolith Monolith vs Microservices by Simon Brown Modularization
36. Applying Microservices Patterns to a Modular Monolith Monolith vs Microservices by Simon Brown Modularization
37. Applying Microservices Patterns to a Modular Monolith Monolith vs Microservices by Simon Brown Modularization
38. Applying Microservices Patterns to a Modular Monolith Cross-pollination between architectures Leverage and reuse work from the microservices world into our modular app
39. Applying Microservices Patterns to a Modular Monolith Domain for example
40. Applying Microservices Patterns to a Modular Monolith Domain for example
41. Applying Microservices Patterns to a Modular Monolith Domain for example
42. Applying Microservices Patterns to a Modular Monolith Domain for example
43. Applying Microservices Patterns to a Modular Monolith Domain for example
44. Applying Microservices Patterns to a Modular Monolith Simple architecture
45. Applying Microservices Patterns to a Modular Monolith Separating domains
46. Applying Microservices Patterns to a Modular Monolith Problems when leaving one database A 
 C 
 I 
 D Local transactions are ensured by
47. Applying Microservices Patterns to a Modular Monolith Problems when leaving one database A 
 C 
 I 
 D Atomicity 
 Consistency 
 Isolation 
 Durability Local transactions are ensured by
48. Applying Microservices Patterns to a Modular Monolith Problems when leaving one database A 
 C 
 I 
 D Atomicity 
 Consistency 
 Isolation 
 Durability Local transactions are ensured by
49. Applying Microservices Patterns to a Modular Monolith Not handling transactions
50. Applying Microservices Patterns to a Modular Monolith Not handling transactions Consistency issues
51. Applying Microservices Patterns to a Modular Monolith Not handling transactions Consistency issues Devolve into f ixing data issues in production
52. Applying Microservices Patterns to a Modular Monolith Not handling transactions Consistency issues Devolve into f ixing data issues in production Important f lows break and we have no way of noticing
53. Applying Microservices Patterns to a Modular Monolith Patterns Proven solutions to recurring problems
54. Applying Microservices Patterns to a Modular Monolith Microservices Patterns
55. Applying Microservices Patterns to a Modular Monolith Microservices Patterns
56. Applying Microservices Patterns to a Modular Monolith What patterns are we going to use?
57. Applying Microservices Patterns to a Modular Monolith What patterns are we going to use? One database per service/domain
58. Applying Microservices Patterns to a Modular Monolith What patterns are we going to use? One database per service/domain Saga
59. Applying Microservices Patterns to a Modular Monolith What patterns are we going to use? One database per service/domain Saga Transactional Outbox
60. Applying Microservices Patterns to a Modular Monolith One database per service/domain Isolation of data structure
61. Applying Microservices Patterns to a Modular Monolith One database per service/domain Private tables per service Isolation of data structure
62. Applying Microservices Patterns to a Modular Monolith One database per service/domain Private tables per service Schema per service Isolation of data structure
63. Applying Microservices Patterns to a Modular Monolith One database per service/domain Private tables per service Schema per service Database per service Isolation of data structure
64. Applying Microservices Patterns to a Modular Monolith Saga Chris Richardson - https://microservices.io/patterns/data/saga.html Eventual consistency across systems
65. Applying Microservices Patterns to a Modular Monolith Saga Chris Richardson - https://microservices.io/patterns/data/saga.html Sequence of local transactions Eventual consistency across systems
66. Applying Microservices Patterns to a Modular Monolith Transactional Outbox Chris Richardson - https://microservices.io/patterns/data/transactional-outbox.html Atomically update state and publish events
67. Applying Microservices Patterns to a Modular Monolith Transactional Outbox Chris Richardson - https://microservices.io/patterns/data/transactional-outbox.html Atomically update state and publish events
68. Applying Microservices Patterns to a Modular Monolith Modular architecture
69. Applying Microservices Patterns to a Modular Monolith Modular architecture To be able to reference a User entity indirectly, it will have the same identi f ier across domains and databases.
70. Applying Microservices Patterns to a Modular Monolith Saga f low
71. Applying Microservices Patterns to a Modular Monolith Saga f low
72. Applying Microservices Patterns to a Modular Monolith Saga f low User con f irms email
73. Applying Microservices Patterns to a Modular Monolith Saga f low User con f irms email
74. Applying Microservices Patterns to a Modular Monolith Saga f low User con f irms email We update the status_code attribute to con f irmed
75. Applying Microservices Patterns to a Modular Monolith Saga f low
76. Applying Microservices Patterns to a Modular Monolith Saga f low Outbox record gets created
77. Applying Microservices Patterns to a Modular Monolith Saga f low
78. Applying Microservices Patterns to a Modular Monolith Saga f low
79. Applying Microservices Patterns to a Modular Monolith Saga f low User record gets created
80. Applying Microservices Patterns to a Modular Monolith Saga f low
81. Applying Microservices Patterns to a Modular Monolith Saga f low Event collaboration
82. Applying Microservices Patterns to a Modular Monolith Saga f low
83. Applying Microservices Patterns to a Modular Monolith Saga f low Successful sequence
84. Applying Microservices Patterns to a Modular Monolith Saga f low Successful sequence Outbox record gets created
85. Applying Microservices Patterns to a Modular Monolith Saga f low
86. Applying Microservices Patterns to a Modular Monolith Saga f low
87. Applying Microservices Patterns to a Modular Monolith Saga f low Rollback sequence
88. Applying Microservices Patterns to a Modular Monolith Saga f low Rollback sequence Outbox record gets created
89. Applying Microservices Patterns to a Modular Monolith Saga f low Rollback sequence
90. Applying Microservices Patterns to a Modular Monolith Saga f low Rollback sequence Update UserRegistration to its previous waiting_for_con f irmation state
91. Applying Microservices Patterns to a Modular Monolith Saga f low Rollback sequence Update UserRegistration to its previous waiting_for_con f irmation state User record gets destroyed
92. Applying Microservices Patterns to a Modular Monolith Saga f low
93. Applying Microservices Patterns to a Modular Monolith Demo
94. Applying Microservices Patterns to a Modular Monolith Demo Implementation of the mentioned domain and app
95. Applying Microservices Patterns to a Modular Monolith Demo Implementation of the mentioned domain and app Rails multi-database support
96. Applying Microservices Patterns to a Modular Monolith Demo Implementation of the mentioned domain and app Rails multi-database support Ka f ka as a message bus
97. Applying Microservices Patterns to a Modular Monolith Demo Implementation of the mentioned domain and app Rails multi-database support Ka f ka as a message bus Ka f ka Connect as the outbox publisher
98. Applying Microservices Patterns to a Modular Monolith Demo Implementation of the mentioned domain and app Rails multi-database support Ka f ka as a message bus Ka f ka Connect as the outbox publisher Kara f ka for consumers
99. Applying Microservices Patterns to a Modular Monolith
100. Applying Microservices Patterns to a Modular Monolith
101. Applying Microservices Patterns to a Modular Monolith How did we accomplish this?
102. Applying Microservices Patterns to a Modular Monolith How did we accomplish this?
103. Applying Microservices Patterns to a Modular Monolith How did we accomplish this?
104. Applying Microservices Patterns to a Modular Monolith Event consumers
105. Applying Microservices Patterns to a Modular Monolith Event consumers
106. Applying Microservices Patterns to a Modular Monolith Event consumers
107. Applying Microservices Patterns to a Modular Monolith Event consumers
108. Applying Microservices Patterns to a Modular Monolith Creating the Outbox record
109. Applying Microservices Patterns to a Modular Monolith Creating the Outbox record
110. Applying Microservices Patterns to a Modular Monolith Creating the Outbox record
111. Applying Microservices Patterns to a Modular Monolith Creating the Outbox record
112. Applying Microservices Patterns to a Modular Monolith Creating the Outbox record
113. Applying Microservices Patterns to a Modular Monolith Creating the Outbox record
114. Applying Microservices Patterns to a Modular Monolith Creating the Member record
115. Applying Microservices Patterns to a Modular Monolith Creating the Member record
116. Applying Microservices Patterns to a Modular Monolith Creating the Member record
117. Applying Microservices Patterns to a Modular Monolith Creating the Member record
118. Applying Microservices Patterns to a Modular Monolith Creating the Member record
119. Applying Microservices Patterns to a Modular Monolith Creating the Member record
120. Applying Microservices Patterns to a Modular Monolith Registration rollback
121. Applying Microservices Patterns to a Modular Monolith Registration rollback
122. Applying Microservices Patterns to a Modular Monolith Where to f ind the code github.com/ rootstrap/ rails-modular-monolith-with-ddd/ tree/ main-saga
123. Guillermo Aguirre - RailsConf 2023 What to take away Applying Microservices Patterns to a Modular Monolith
124. Guillermo Aguirre - RailsConf 2023 What to take away 3 widely used patterns Applying Microservices Patterns to a Modular Monolith
125. Guillermo Aguirre - RailsConf 2023 What to take away 3 widely used patterns Dealing with distributed transactions Applying Microservices Patterns to a Modular Monolith
126. Guillermo Aguirre - RailsConf 2023 What to take away 3 widely used patterns Dealing with distributed transactions It's possible to leverage di ff erent solutions Applying Microservices Patterns to a Modular Monolith
127. Guillermo Aguirre - RailsConf 2023 What to take away 3 widely used patterns Dealing with distributed transactions It's possible to leverage di ff erent solutions Not a silver bullet Applying Microservices Patterns to a Modular Monolith
128. Guillermo Aguirre - RailsConf 2023 What to take away 3 widely used patterns Dealing with distributed transactions It's possible to leverage di ff erent solutions Not a silver bullet Inspiring others Applying Microservices Patterns to a Modular Monolith
129. Guillermo Aguirre - RailsConf 2023 Thank you! Applying Microservices Patterns to a Modular Monolith @guillermoap @guillermoap_ @guillermo.aguirre Guillermo Aguirre /gee-SHER-moh ah-GHEE-rreh/