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Stuff About CQRS
- 1. Stuff About CQRS Jak Charlton @JakCharlton jak@thinkddd.com
- 2. Disclaimer: This Isn’t All About Command Query Responsibility Segregation
- 3. does anyone here even know what CQRS is anyway, or were the other sessions full?
- 4. Another Disclaimer: There won’t be any code, I don’t do code, just opinions
- 6. My Objective Today is to Make You Think
- 7. My Objective Today is to Make You Think “Maybe There Is A Better Way?”
- 8. Why Don’t We Talk Like “Normal” People Do?
- 9. Why Don’t We Talk Like “Normal” People Do? Developers are usually techy
- 10. Why Don’t We Talk Like “Normal” People Do? Developers are usually techy Business people usually don’t understand “techy”
- 11. Why Don’t We Talk Like “Normal” People Do? Developers are usually techy Business people usually don’t understand “techy” So why do we try to make them think like we do?
- 12. Why Does Language Matter So Much?
- 13. Why Does Language Matter So Much? Without language, we cannot convey meaning
- 14. Why Does Language Matter So Much? Without language, we cannot convey meaning But when we talk different languages, we lose in the translation
- 15. Why Does Language Matter So Much? Without language, we cannot convey meaning But when we talk different languages, we lose in the translation Let’s agree on one
- 16. How Do “Normal” People See the World?
- 17. How Do “Normal” People See the World? People don’t think in terms of “data”
- 18. How Do “Normal” People See the World? People don’t think in terms of “data” People think “tasks”
- 19. How Do “Normal” People See the World? People don’t think in terms of “data” People think “tasks” People are objective based, only computers work on data
- 20. Otherwise Known As “Grid Abuse”
- 21. Otherwise Known As “Grid Abuse” Grids are a UI problem created by developers
- 22. Otherwise Known As “Grid Abuse” Grids are a UI problem created by developers People don’t see information in columns and rows
- 23. Otherwise Known As “Grid Abuse” Grids are a UI problem created by developers People don’t see information in columns and rows Even Excel doesn’t force you to think that way
- 24. If People Don’t Think In Grids, Why Force Data Into Grids?
- 25. If People Don’t Think In Grids, Why Force Data Into Grids? Developers are ingrained with RDBMS Rows and Columns
- 26. If People Don’t Think In Grids, Why Force Data Into Grids? Developers are ingrained with RDBMS Rows and Columns Business information doesn’t come in rows and columns
- 27. If People Don’t Think In Grids, Why Force Data Into Grids? Developers are ingrained with RDBMS Rows and Columns Business information doesn’t come in rows and columns We forced them to store and use it that way
- 29. Thinking About NoSQL Databases If users think about things like “my documents” maybe we should just store stuff that way?
- 30. Thinking About NoSQL Databases If users think about things like “my documents” maybe we should just store stuff that way? NoSQL databases let us concentrate on what to store, not how
- 31. Quick Summary
- 32. Quick Summary People need to communicate
- 33. Quick Summary People need to communicate People think Tasks
- 34. Quick Summary People need to communicate People think Tasks People think “stuff” or “documents” or “things”
- 35. What Does This Have to Do With CQRS ???
- 36. What Does This Have to Do With CQRS ??? Not much ...
- 37. What Does This Have to Do With CQRS ??? Not much ... Yet...
- 38. What Does This Have to Do With CQRS ??? Not much ... Yet... One more step... now we get a bit techy
- 39. CAP Theory
- 40. CAP Theory Consistency: The client perceives that a set of operations has occurred all at once.
- 41. CAP Theory Consistency: The client perceives that a set of operations has occurred all at once. Availability: Every operation must terminate in an intended response.
- 42. CAP Theory Consistency: The client perceives that a set of operations has occurred all at once. Availability: Every operation must terminate in an intended response. Partition tolerance: Operations will complete, even if individual components are unavailable.
- 43. CAP Theory Consistency: The client perceives that a set of operations has occurred all at once. Availability: Every operation must terminate in an intended response. Partition tolerance: Operations will complete, even if individual components are unavailable. You cannot have all three
- 44. ACID
- 45. ACID Atomic, Consistent, Isolated, Durable
- 46. ACID Atomic, Consistent, Isolated, Durable In CAP Theory terms ACID gives you:
- 47. ACID Atomic, Consistent, Isolated, Durable In CAP Theory terms ACID gives you: Consistency and Availability
- 48. ACID Atomic, Consistent, Isolated, Durable In CAP Theory terms ACID gives you: Consistency and Availability But Sacrifices Partition Tolerance
- 49. BASE
- 50. BASE Basically Available, Soft state, Eventually consistent
- 51. BASE Basically Available, Soft state, Eventually consistent In CAP Theory BASE gives you:
- 52. BASE Basically Available, Soft state, Eventually consistent In CAP Theory BASE gives you: Availability and Partition Tolerance
- 53. BASE Basically Available, Soft state, Eventually consistent In CAP Theory BASE gives you: Availability and Partition Tolerance But Sacrifices Consistency
- 55. Command Query Responsibility Segregation Bertrand Meyer principle of CQS: every method should either be a command that performs an action, or a query that returns data to the caller
- 56. Command Query Responsibility Segregation Bertrand Meyer principle of CQS: every method should either be a command that performs an action, or a query that returns data to the caller At an architectural level this means: either issue commands, or issue queries, but never both
- 57. Command Query Responsibility Segregation Bertrand Meyer principle of CQS: every method should either be a command that performs an action, or a query that returns data to the caller At an architectural level this means: either issue commands, or issue queries, but never both And, query from a separate source from your domain commands
- 58. CQRS and BASE
- 59. CQRS and BASE CQRS gives us BASE at an architectural level
- 60. CQRS and BASE CQRS gives us BASE at an architectural level We may not always be consistent
- 61. CQRS and BASE CQRS gives us BASE at an architectural level We may not always be consistent But most data isn’t consistent in reality anyway, we just think it is
- 62. CQRS and BASE CQRS gives us BASE at an architectural level We may not always be consistent But most data isn’t consistent in reality anyway, we just think it is Eventually our architecture will be consistent
- 63. CQRS in a Picture Client Command Queries Domain Event Handlers Event Handlers Publish (synchronous no bus) Persist Update Domain Persistence Read Model
- 64. CQRS in a Simpler Picture Domain Events Read Model Co Os m m DT an ds Client
- 65. What Did All That Beginning Stuff Have to Do With CQRS ???
- 66. What Did All That Beginning Stuff Have to Do With CQRS ??? The way people think matters
- 67. What Did All That Beginning Stuff Have to Do With CQRS ??? The way people think matters CQRS splits actions from queries
- 68. What Did All That Beginning Stuff Have to Do With CQRS ??? The way people think matters CQRS splits actions from queries And people think about asking people to do things or asking them for information
- 69. Benefits of CQRS
- 70. Benefits of CQRS Simplified Architecture
- 71. Benefits of CQRS Simplified Architecture Closer Alignment with Users
- 72. Benefits of CQRS Simplified Architecture Closer Alignment with Users Performance
- 73. Benefits of CQRS Simplified Architecture Closer Alignment with Users Performance Scalability
- 74. Benefits of CQRS Simplified Architecture Closer Alignment with Users Performance Scalability Eliminates a leaky abstraction
- 75. My Objective Today was to Make You Think
- 76. My Objective Today was to Make You Think “Maybe There Is A Better Way?”
- 77. My Objective Today was to Make You Think “Maybe There Is A Better Way?” I Hope I Succeeded
- 78. DeveloperDeveloperDeveloper! Events would not be possible With out the generous support from our sponsors… We would like to thank the following for their support:
Editor's Notes
- CQRS is a technical approach that solves a lot of problems But it requires something more, a better way of working So this presentation is more about how to think differently
- You don’t ring your bank and say “I want you to view my customer record, edit the address fields and save it to your database” You do call your bank and say “I would like to change my correspondence address”
- You don’t ring your bank and say “I want you to view my customer record, edit the address fields and save it to your database” You do call your bank and say “I would like to change my correspondence address”
- You don’t ring your bank and say “I want you to view my customer record, edit the address fields and save it to your database” You do call your bank and say “I would like to change my correspondence address”
- Users think of lists of information ... my tweets, my bank account transaction, my facebook wall, my auctions, my Documents This abuse extends to many areas of a business - we have abused users into talking our way, not theirs
- Users think of lists of information ... my tweets, my bank account transaction, my facebook wall, my auctions, my Documents This abuse extends to many areas of a business - we have abused users into talking our way, not theirs
- Users think of lists of information ... my tweets, my bank account transaction, my facebook wall, my auctions, my Documents This abuse extends to many areas of a business - we have abused users into talking our way, not theirs
- Store data in a loose fashion Only store what you need In the format you want
- Store data in a loose fashion Only store what you need In the format you want