Dependency Injection in Nameko

Nameko is a python framework for building service-oriented software, developed by onefinestay. This talk explains how nameko uses Dependency Injection, why it's an important paradigm and how it simplifies writing services and testing them.

More info at https://github.com/onefinestay/nameko

Transcript

1. Dependency Injection in Nameko Matt Bennett ~ Senior Engineer ~ onefinestay
2. Dependency Injection Design pattern whereby an object's dependencies are injected or passed by reference into it, rather than constructed by the object. c l a s s W i d g e t ( o b j e c t ) : d e f _ _ i n i t _ _ ( s e l f ) : s e l f . s e s s i o n = g e t _ d b _ s e s s i o n ( ) c l a s s W i d g e t ( o b j e c t ) : d e f _ _ i n i t _ _ ( s e l f , s e s s i o n ) : s e l f . s e s s i o n = s e s s i o n Pretty simple
3. Nameko Python framework for building service- oriented software Bookings Payments Homes Open-source software Active development on GitHub
4. Nameko out of the box Everything you need to do: AMQP RPC AMQP Pub-Sub Bookings Payments Homes
5. Definitions Entrypoints To interact with a service Dependencies For the service to interact with external things
6. Example Service f r o m n a m e k o . r p c i m p o r t r p c f r o m . d e p e n d e n c i e s i m p o r t d a t a b a s e _ c o n n e c t i o n c l a s s H e l l o S e r v i c e ( o b j e c t ) : d a t a b a s e = d a t a b a s e _ c o n n e c t i o n ( D B _ U R I ) @ r p c d e f h e l l o ( s e l f , n a m e ) : s e l f . d a t a b a s e . a d d ( n a m e ) r e t u r n " H e l l o , { } " . f o r m a t ( n a m e )
7. Running HelloService f r o m n a m e k o . c o n t a i n e r s i m p o r t S e r v i c e C o n t a i n e r c o n f i g = { ' A M Q P _ U R I ' : ' a m q p : / / g u e s t : g u e s t @ l o c a l h o s t : 5 6 7 2 / ' } c o n t a i n e r = S e r v i c e C o n t a i n e r ( H e l l o S e r v i c e , . . . , c o n f i g ) c o n t a i n e r . s t a r t ( ) . . .
8. Worker Lifecycle 1. Entrypoint "fires" 2. Worker created 3. Dependencies injected 4. Execute method 5. Discard worker w o r k e r _ i n s t a n c e = H e l l o S e r v i c e ( ) w o r k e r _ i n s t a n c e . d a t a b a s e = H e l l o S e r v i c e . d a t a b a s e . i n j e c t ( ) r e s u l t = w o r k e r _ i n s t a n c e . h e l l o ( n a m e ) d e l w o r k e r _ i n s t a n c e
9. Why do it this way? Simple service logic Complex application f r o m n a m e k o . r p c i m p o r t r p c f r o m . d e p e n d e n c i e s i m p o r t d a t a b a s e _ c o n n e c t i o n c l a s s H e l l o S e r v i c e ( o b j e c t ) : d a t a b a s e = d a t a b a s e _ c o n n e c t i o n ( D B _ U R I ) @ r p c d e f h e l l o ( s e l f , n a m e ) : s e l f . d a t a b a s e . a d d ( n a m e ) r e t u r n " H e l l o , { } " . f o r m a t ( n a m e ) Separation of concerns
10. Unit Testing Testing a service in isolation f r o m m o c k i m p o r t c a l l f r o m n a m e k o . t e s t i n g . s e r v i c e s i m p o r t w o r k e r _ f a c t o r y h e l l o _ s v c = w o r k e r _ f a c t o r y ( H e l l o S e r v i c e ) a s s e r t h e l l o _ s v c . h e l l o ( " M a t t " ) = = " H e l l o , M a t t " a s s e r t h e l l o _ s v c . d a t a b a s e . a d d . c a l l _ a r g s _ l i s t = = [ c a l l ( " M a t t " ) ] f r o m n a m e k o . t e s t i n g . s e r v i c e s i m p o r t w o r k e r _ f a c t o r y d a t a b a s e = s e t ( ) h e l l o _ s v c = w o r k e r _ f a c t o r y ( H e l l o S e r v i c e , d a t a b a s e = d a t a b a s e ) a s s e r t h e l l o _ s v c . h e l l o ( " M a t t " ) = = " H e l l o , M a t t " a s s e r t d a t a b a s e = = { " M a t t " }
11. Integration Testing Testing a service with something else Host services the "normal" way Restrict scope of interaction through dependencies
12. Replace Injections f r o m n a m e k o . t e s t i n g . s e r v i c e s i m p o r t r e p l a c e _ i n j e c t i o n s c o n t a i n e r = S e r v i c e C o n t a i n e r ( B o o k i n g S e r v i c e , . . . ) p u b l i s h e r _ m o c k = r e p l a c e _ i n j e c t i o n s ( c o n t a i n e r , " h o m e s _ p u b l i s h e r " ) c o n t a i n e r . s t a r t ( ) . . . Bookings Payments Homes
13. Worker Lifecycle All dependencies participate worker setup worker result worker teardown
14. Nice Examples Log Aggregator Sentry Reporter Statsd Monitor
15. Summary Dependency Injection Simple idea Separation of concerns Nameko Encourages explicit dependencies Provides nice testing tools And other goodies... Nameko Workshop -- Tomorrow 10:20, MADE room
16. Thanks! Questions? https://github.com/onefinestay/nameko P.S. onefinestay are hiring...