Microservices ? Think twice !

[ Meetup : https://www.meetup.com/fr-FR/Linkvalue-tech/events/234775447/ (FR) ]
[ Video : https://youtu.be/uTT8gJT6Adk (FR) ]

After 1 year building microservices, I would like to share a few topics that you should consider before moving from your monolith :

- Is it suited for your organisation?
- Do you know how to properly enforce their autonomy?
- Have you found your "bounded contexts" (DDD notion) that may turn into your spliting points?
- Are you ready to handle the complexity they add, such as a bigger dev-ops stack, a harder failure handling or end-to-end testing?

I may have a few tips for you, and really hope to convince you to double check your knowledge before moving too fast ;)

Transcript

1. JEAN-MARIE LAMODIERE Build microservices since 07/2015 @JMLamodiere MICROSERVICES? THINK TWICE! Linkvalue | Jean-Marie Lamodière 1 Les microservices, c'est pas automatique ! 1935 CP Committed to innovate LINKVALUE
2. Linkvalue | Jean-Marie Lamodière ASHAMED OF YOUR MONOLITH?  Spaghetti code  Side effects  Team velocity decreasing  Hard to refactor  Bugs 2
3. Linkvalue | Jean-Marie Lamodière 3
4. Linkvalue | Jean-Marie Lamodière 4
5. Linkvalue | Jean-Marie Lamodière PROBLEMS THEY SOLVE 1.Autonomy 2.Autonomy 3.Autonomy 5
6. Linkvalue | Jean-Marie Lamodière PROBLEMS THEY SOLVE 1.Autonomy : deployment 2.Autonomy : langage, framework 3.Autonomy : scalability 6
7. Linkvalue | Jean-Marie Lamodière 7
8. Linkvalue | Jean-Marie Lamodière WHY AUTONOMY MATTERS?  Loosely coupled organisation = less coupled systems  Quality audit on windows vista : organizational structures = most important factor!  Team accountability 8
9. Linkvalue | Jean-Marie Lamodière OTHER KEY BENEFITS  Easier for newcomers  Allows isolated POC  Teams scalability  Simpler code design  Easy refactoring 9
10. Linkvalue | Jean-Marie Lamodière WHO USES IT?  Uber  Netflix  Amazon  Ebay  Sound Cloud  Groupon 10  Guilt  Zalando  Spotify  Meetic  M6 Web  Auchan
11. Linkvalue | Jean-Marie Lamodière « Trade-offs » appears 24x in « Building Microservices » book 11
12. Linkvalue | Jean-Marie Lamodière 12
13. Linkvalue | Jean-Marie Lamodière TESTIMONY (45' talks published on )  « We had to fall back to a monolith, and retry when ready » – SAMUEL ROZE PHP Tour 2016 • Prenons soin de nos microservices  « I wish I had known... » – MATT RANNEY GOTO 2016 • What I Wish I Had Known Before Scaling Uber to 1000 Services 13
14. Linkvalue | Jean-Marie Lamodière 14
15. Linkvalue | Jean-Marie Lamodière WHAT IS SO COMPLEX ?  Boundaries : hard to find / change  Huuuge dev-ops stack  Distributed system  Failure handling  Monitoring  End-to-end testing 15
16. Linkvalue | Jean-Marie Lamodière 16
17. Linkvalue | Jean-Marie Lamodière BOUNDARIES : WHERE TO SPLIT?  Splitting = hard to change  Size ? Small enough, not smaller  Splitting by technical layers? no!  Things that should change together (« S » in S.O.L.I.D.)  Loose coupling, high cohesion 17
18. Linkvalue | Jean-Marie Lamodière DDD* TO THE RESCUE! (* Domain Driven Design) Toolset to help domain experts and developers to refine and share domain knowledge, reflect it in the code base, and prioritize efforts. 18
19. Linkvalue | Jean-Marie Lamodière MAKE THE IMPLICIT, EXPLICIT! 19 Copyright @DDDreboot ;)
20. Linkvalue | Jean-Marie Lamodière SPLIT BY BOUNDED CONTEXT  Bounded context = Team sharing the same « ubiquitous language » (same terms)  Vertical, business-focus slice 20
21. Linkvalue | Jean-Marie Lamodière WHEN TO SPLIT ?  When ready : technical stack chosen, architectural decisions taken, devs and ops willing to go, autonomous 2 pizza feature teams  When sure of a splitting point  Start with a monolith (!) to find them 21
22. Linkvalue | Jean-Marie Lamodière CONWAY'S LAW « Organizations which design systems are constrained to produce designs which are copies of the communication structures of these organizations » 22
23. Linkvalue | Jean-Marie Lamodière 2ND LAW OF CONSULTING (Gerald Weinberg) 23
24. Linkvalue | Jean-Marie Lamodière SPLITTING STRATEGY  Implement double-writing (microservice or legacy side)  Publish needed messages  One-shot data import script  Assert data is sync  Read from microservice 24
25. Linkvalue | Jean-Marie Lamodière COMMUNICATION BETWEEN µS  No shared database!  Language agnostic (ex : rest / json)  If weakly typed (json), have a clear doc (optional? nullable?) or json-schema  Keep consistency. ex : pagination  Define minimal customer-centric api 25
26. Linkvalue | Jean-Marie Lamodière COMMUNICATION BETWEEN µS 26
27. Linkvalue | Jean-Marie Lamodière 27
28. Linkvalue | Jean-Marie Lamodière SYNCHRONOUS COMMUNICATION - PROS -  Easier to understand (= method call)  Easier transition from monolith  Instant feedback to the client 28
29. Linkvalue | Jean-Marie Lamodière SYNCHRONOUS COMMUNICATION 29 29 User Optin Other service depending on 1 optin Register Register french user Read 1 optin Read
30. Linkvalue | Jean-Marie Lamodière SYNCHRONOUS COMMUNICATION - CONS -  Fanout : 1% slow calls more probable when cascading calls  Beware of coupling !  Beware of distributed monolith !! 30
31. 31 « Distributed monolith » @tiffyshindo
32. Linkvalue | Jean-Marie Lamodière ASYNCHRONOUS COMMUNICATION  Message broker  Reactive : event driven  Choregraphy over orchestration  Autonomy over authority : each service copy the data it needs  Work well with CQRS / ES 32
33. Linkvalue | Jean-Marie Lamodière ASYNCHRONOUS COMMUNICATION 33 Message broker Message broker Message broker Message broker User French user registered Optin User optins changed Other service depending on 1 optin Register Read
34. Linkvalue | Jean-Marie Lamodière COMMUNICATION TRAPS  Chatty communication = coupling feature envy, wrong splitting…  Perf overhead : define « acceptable » 34
35. Linkvalue | Jean-Marie Lamodière 35
36. Linkvalue | Jean-Marie Lamodière DESIGN FOR FAILURE  It will fail, have a plan!  Define what to do, to return  Define timeout for each call  Message hospital (dead letter queue)  Circuit breaker / back pressure  Blameless culture needed 36
37. Linkvalue | Jean-Marie Lamodière NETFLIX CHAOS MONKEY  Randomly shut down services  Cure developers optimism ;) 37
38. Linkvalue | Jean-Marie Lamodière SERVICE DISCOVERY  Each µs scales individualy : which IP should we call ?  DNS in front of a load-balancer  Kubernetes services  Docker Swarm discovery (libkv + consul/etcd/zookeeper) 38
39. Linkvalue | Jean-Marie Lamodière CAP THEOREM (Distributed Systems)  Choose 2 between consistency (C), availability (A) and partition (P)  Avoid distributed transactions  Embrase eventual consistency  Use idempotent operations  Worker to clean inconsistency 39
40. Linkvalue | Jean-Marie Lamodière 40
41. Linkvalue | Jean-Marie Lamodière MICROSERVICES CLIENTS  Libraries ok, 1 per language needed  No business logic in client : avoid anemic CRUD microservices  To call a complex api (legacy, external), build a facade service 41
42. Linkvalue | Jean-Marie Lamodière CHANGE PROOF CLIENTS  Old and new api should cohexist  Postel's law : « be conservative in what you do, be liberal in what you accept from others »  Tolerant reader (Martin Fowler) : ignore changes not impacting you 42
43. Linkvalue | Jean-Marie Lamodière CHANGE PROOF CLIENTS 43
44. Linkvalue | Jean-Marie Lamodière API GATEWAY  Avoid exposing µs to frontend  Hide spliting to new microservices  Handle authentication / roles  Pro-tips : Back-end for frontend, 1 gateway per front application 44
45. Linkvalue | Jean-Marie Lamodière API GATEWAY 45 Microservice Legacy Monolith Microservice Microservice Android API Gateway Android application Public Private ReactJS Web application ReactJS API Gateway
46. Linkvalue | Jean-Marie Lamodière 46
47. Linkvalue | Jean-Marie Lamodière TESTING A MICROSERVICE  No end-to-end testing at µs level  Stub/mock others µs in functional tests  Have consumer-driven tests  No continuous integration = no µs!  One c.i. pipeline per microservice 47
48. Linkvalue | Jean-Marie Lamodière END TO END TESTING  Test journeys (main features), not user stories (already tested)  Goal : check wiring  Should be done in each front app  Can run in production 48
49. Linkvalue | Jean-Marie Lamodière TESTING = TRUST 49 Involve a quality assurance member in your feature team
50. Linkvalue | Jean-Marie Lamodière ARCHITECT ROLE  Keep µs map up to date  Define communication between µs  Define automatic deploying, monitoring and logging strategy  Adapt to change, like a city planner  Enforce team autonomy inside a µs 50
51. Linkvalue | Jean-Marie Lamodière 51
52. Linkvalue | Jean-Marie Lamodière WHAT SHOULD µS KEEP COMMON ?  Rules : communication, logs...  Template to create new µs, but no synchronization afterward  Violate DRY accross µs !  Shared code = coupling  Priority : autonomy 52
53. Linkvalue | Jean-Marie Lamodière MONITORING / LOGGING TIPS  Pass a unique « correlation id » to each sub-calls, including messages and asynchronous calls  Make sure your APM supports each language + versions  Have a look at Sysdig.org 53
54. Linkvalue | Jean-Marie Lamodière 54  Extreme Programming  TDD / BDD  S.O.L.I.D.  Loose coupling, high cohesion  DDD  Hexagonal
55. Linkvalue | Jean-Marie Lamodière BEFORE YOU START  microservices.io  martinfowler.com /microservices/ /articles/microservices.html /articles/microservice-trade-offs.html  groups.google.com /forum/#!forum/microservices 55
56. Linkvalue | Jean-Marie Lamodière ASYNCHRONOUS COMMUNICATION  blog.christianposta.com Why Microservices Should Be Event Driven:Autonomy vs Authority  reactivemanifesto.org 56 Lightbend.com (free)
57. Linkvalue | Jean-Marie Lamodière TALKS  What I Wish I Had Known Before Scaling Uber to 1000 Services GOTO 2016 • Matt Ranney  Prenons soin de nos microservices PHP Tour 2016 • SAMUEL ROZE  Meetic backend mutation with Symfony SymfonyLive 2015 • J. Calabrese E. Broutin  Kafka event architecture at Meetic Forum PHP 2015 • B. Pineau M. Robin 57
58. Linkvalue | Jean-Marie Lamodière DDD RECOMMENDED BOOKS 58 leanpub.com (free)
59. Thank you! Linkvalue | Jean-Marie Lamodière 59 Committed to innovate LINKVALUE JEAN-MARIE LAMODIERE Build microservices since 07/2015 @JMLamodiere 1935 CP