Rack Middleware as a General Purpose Abstraction

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" summary

Argues that Rack-style middleware is a general abstraction that replaces sprawling classes and fragile mixins, demonstrated by Vagrant where commands compose as a Builder of 22 middleware components passing a shared state bag; each middleware has an initialize and call, is trivial to unit test, and shows clear ordering and reuse (suspend reuses top middlewares from up). Also describes an inserted Warden error recovery layer that handles exceptions and signals so middleware unwinds cleanly — used in production Vagrant and reduces complexity while remaining performant enough.

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" chapters (16)

1. 0:00Start
2. 2:16Problems
3. 2:48Unclear dependencies
4. 3:17Difficult to Test
5. 3:56Mixin all the things!
6. 9:53Function Composition Applied to Large Classes?
7. 10:38Python Web Server Gateway Interface v1.0
8. 10:55Request Processing
9. 13:38Explicit Ordering
10. 14:03Visible Dependencies
11. 14:57Easily Tested
12. 15:55Extensible: Subclass!
13. 16:12Virtual Machine Lifecycle
14. 19:46Scared?
15. 24:14Reuse
16. 24:55Serial Invocations

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