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Stuff About CQRS
- 1. Stuff About CQRS Jak Charlton @JakCharlton jak@thinkddd.com
- 2. Disclaimer: This Isn’t AllAbout Command Query Responsibility Segregation
- 3. does anyone hereeven know what CQRS is anyway, or were the other sessions full?
- 4. Another Disclaimer: There won’tbe any code, I don’t do code, just opinions
- 5.
- 6. My Objective Today isto Make You Think
- 7. My Objective Today isto Make You Think “Maybe There Is A Better Way?”
- 8. Why Don’t WeTalk Like “Normal” People Do?
- 9. Why Don’t WeTalk Like “Normal” People Do? Developers are usually techy
- 10. Why Don’t WeTalk Like “Normal” People Do? Developers are usually techy Business people usually don’t understand “techy”
- 11. Why Don’t WeTalk 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’tThink In Grids, Why Force Data Into Grids?
- 25. If People Don’tThink In Grids, Why Force Data Into Grids? Developers are ingrained with RDBMS Rows and Columns
- 26. If People Don’tThink 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’tThink 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
- 28.
- 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.
- 32. Quick Summary People needto communicate
- 33. Quick Summary People needto communicate People think Tasks
- 34. Quick Summary People needto communicate People think Tasks People think “stuff” or “documents” or “things”
- 35. What Does ThisHave to Do With CQRS ???
- 36. What Does ThisHave to Do With CQRS ??? Not much ...
- 37. What Does ThisHave to Do With CQRS ??? Not much ... Yet...
- 38. What Does ThisHave to Do With CQRS ??? Not much ... Yet... One more step... now we get a bit techy
- 39.
- 40. CAP Theory Consistency: The clientperceives that a set of operations has occurred all at once.
- 41. CAP Theory Consistency: The clientperceives that a set of operations has occurred all at once. Availability: Every operation must terminate in an intended response.
- 42. CAP Theory Consistency: The clientperceives 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 clientperceives 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.
- 45.
- 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.
- 50. BASE Basically Available, Softstate, Eventually consistent
- 51. BASE Basically Available, Softstate, Eventually consistent In CAP Theory BASE gives you:
- 52. BASE Basically Available, Softstate, Eventually consistent In CAP Theory BASE gives you: Availability and Partition Tolerance
- 53. BASE Basically Available, Softstate, Eventually consistent In CAP Theory BASE gives you: Availability and Partition Tolerance But Sacrifices Consistency
- 54.
- 55. Command Query Responsibility Segregation BertrandMeyer 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 BertrandMeyer 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 BertrandMeyer 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.
- 59. CQRS and BASE CQRSgives us BASE at an architectural level
- 60. CQRS and BASE CQRSgives us BASE at an architectural level We may not always be consistent
- 61. CQRS and BASE CQRSgives 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 CQRSgives 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 aPicture Client Command Queries Domain Event Handlers Event Handlers Publish (synchronous no bus) Persist Update Domain Persistence Read Model
- 64. CQRS in aSimpler Picture Domain Events Read Model Co Os m m DT an ds Client
- 65. What Did AllThat Beginning Stuff Have to Do With CQRS ???
- 66. What Did AllThat Beginning Stuff Have to Do With CQRS ??? The way people think matters
- 67. What Did AllThat Beginning Stuff Have to Do With CQRS ??? The way people think matters CQRS splits actions from queries
- 68. What Did AllThat 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.
- 70. Benefits of CQRS SimplifiedArchitecture
- 71. Benefits of CQRS SimplifiedArchitecture Closer Alignment with Users
- 72. Benefits of CQRS SimplifiedArchitecture Closer Alignment with Users Performance
- 73. Benefits of CQRS SimplifiedArchitecture Closer Alignment with Users Performance Scalability
- 74. Benefits of CQRS SimplifiedArchitecture Closer Alignment with Users Performance Scalability Eliminates a leaky abstraction
- 75. My Objective Today wasto Make You Think
- 76. My Objective Today wasto Make You Think “Maybe There Is A Better Way?”
- 77. My Objective Today wasto Make You Think “Maybe There Is A Better Way?” I Hope I Succeeded
- 78. DeveloperDeveloperDeveloper! Events wouldnot be possible With out the generous support from our sponsors… We would like to thank the following for their support:
Editor's Notes
- #2 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
- #14 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”
- #15 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”
- #16 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”
- #17 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
- #18 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
- #19 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
- #23 Store data in a loose fashion Only store what you need In the format you want
- #24 Store data in a loose fashion Only store what you need In the format you want