From macro to micro goto
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From Macro To Micro Sam Newman ThoughtWorks
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From Macro To Micro
Sam Newman ThoughtWorks
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Durability
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Technology
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Geography
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Team Structure & Organisation
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Speed Of Change
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http://bit.ly/GeeCon2012SamN
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What makes a good service?
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High Cohesion
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Loose Coupling
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Bounded Context
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"The delimited applicability of a particular model. BOUNDING CONTEXTS gives team members a clear and shared understanding of what has to be consistent and what can develop independently."
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A specific responsibility enforced by explicit boundaries
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http://www.sapiensworks.com/blog/post/2012/04/17/DDD-The-Bounded-Context-Explained.aspx
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Music Library
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MusikShopMono
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Warehouse Finance
Catalog Recommendation
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That was the easy bit
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Enter the DB
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DB
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DB Schema
Recomendation Service
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DB Schema
Recomendation ServiceMusicShopMono
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DB Schema
Recomendation ServiceMusicShopMono
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DB
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Catalog Recommendation
Repository
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Catalog
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Catalog
Line Items
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Catalog Finance
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Catalog Finance
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Catalog Finance
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Catalog Finance
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Catalog Finance
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Catalog Service Finance Service
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Catalog Service Finance Service
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Catalog Service Finance Service
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Line Items
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Catalog Service Finance Service
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Catalog Service Finance Service
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/sku/185
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Catalog
Finance
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Country Codes
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Catalog
FinanceWarehouse
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Catalog
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Finance Warehouse
Customer Record
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reify
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Finance Warehouse
Customer Record
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Finance Warehouse
Customer Record
Customer
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Warehouse ServiceFinance Service
MusikShop System
Customer Service
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Catalog Warehouse
Item
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Catalog Warehouse
Item
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Bee Gees Hits | $4.99 | 45
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Catalog Warehouse
Item
MusikShop
Bee Gees Hits | $4.99 | 45
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Catalog Warehouse
Item
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Bee Gees Hits | $4.99 | 45
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Catalog Warehouse
Catalog Item
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Stock Levels
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DB
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DB
Cost Of Change
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Microservices
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UNIX Way
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“This is the Unix philosophy: Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface”
- Douglas McIlroy!
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Rule of Modularity: Developers should build a program out of simple parts connected by well defined interfaces, so problems are local, and parts of the program can be replaced in future versions to support new features. This rule aims to save time on debugging complex code that is complex, long, and unreadable.
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Rule of Simplicity: Developers should design for simplicity by looking for ways to break up program systems into small, straightforward cooperating pieces. This rule aims to discourage developers’ affection for writing “intricate and beautiful complexities” that are in reality bug prone programs.
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Rule of Parsimony: Developers should avoid writing big programs. This rule aims to prevent overinvestment of development time in failed or suboptimal approaches caused by the owners of the program’s reluctance to throw away visibly large pieces of work. Smaller programs are not only easier to optimize and maintain; they are easier to delete when deprecated.
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ls
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ls | grep “Sam”
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200 lines of code
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Recommendation - Now With Added
Clojure!
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Test!
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Alert!!!
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UP
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DOWN
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UP?
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UP? DOWN?
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Number >> Size
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Summary
- Identify your bounded contexts
- Understand the cost of change - and do just enough up front thinking!
- This is an incremental journey - you won’t get it right first time
- While size is important, number of services is often the limiting factor
[email protected] @samnewman
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