Software Architecture
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Taking the role of a software architect for the last 10 years starting at a small startup moving to Amdocs OSS devision and then to Wix as chief architect, I have gained some understanding of what it makes to do architecture. I can say today that software architecture is not about * UML * Those huge system box diagrams * Writing documents I count 4 different types of software architecture - each of the four is complex and can make a full presentation by itself. + System architecture - the actual layout of process on hosts - what is a service, number of instances, how services collaborate, etc. + Data architecture - the selection of data storage engines and their usage + Build architecture - the dependencies between different artifacts and their impact on development and deployment + Network architecture - the structure of your layer 1, 2 and 3 network with higher level services (Routers, VLANS, VPNs, etc). I propose talking about software architecture - what is it, what practices and challenges an architect should focus on and how to bring value to an R&D organization. Resource management, self healing systems, containment of failure, architecture vs organization, etc.
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Software Architecture
- 1. So#ware Architecture Reversim Summit 2014
- 2. Why do we need architecture? What it is good for? Is there a role for an Architect?
- 3. Architecture is both the process and the product of planning, designing, and construcBng buildings and other physical structures.
- 4. Architecture is both the process and the product of planning, designing, and construcBng so#ware products and other so#ware systems.
- 5. Is this soDware architecture?
- 6. • It looks like a blueprint Is this soDware architecture?
- 7. However • The main funcBon of a building is sta4c • The main funcBon of soDware is dynamic – Good soDware react to user input and different external events – SoDware evolves with Bme A Blueprint is not a good representa4on of so#ware architecture! Is this soDware architecture?
- 8. What is SoDware Architecture? • Code dependencies • TesBng dependencies • Deployment dependencies • VPNs • VLANs • Routers • Switches • CP vs AP • Data layout • OpBmizaBon • Process interacBons • SLA • Data centers • Failure recovery RunBme Data Build Network
- 9. RunBme Architecture It’s about the runBme construcBon of soDware • A soDware system is built of OS processes – Deployed on one or more hosts • The Processes collabora4on is the so#ware system – InteracBons via RPC, web services, MQs, BUS, shared memory, files, etc. • Process interacBons with data storage – Databases, NoSQL engines, disks, data store APIs • Reverse Proxies, Service Bus – Non-‐funcBonal facilitators of interacBons between processes
- 10. ConsideraBons for RunBme Architecture • Resource Management and Capacity Planning – CPU, disk & network (IO), resource pools (threads, DB connecBons) • Service Level Requirements / Agreements – Availability requirements, DRP, performance, etc. • OrganizaBonal Structure • When shit hits the fans – Self healing systems vs terminal failures – Containment of failures • “Browser land” – Security & cross domain constraints • CAP Theorem • Note: cache is not part of an architecture – it is an opBmizaBon
- 11. Data Architecture It’s about your data • What is your data? • What is the structure of the data? – RelaBonal, columnar, doc, key/value, events, search index, queues, graph, logs, unstructured, pictures, CRDTs … Create Cart Add item Add item Remove item checkout key value key value key value key value key value Column 1 2 Noddle 1 Pig Spider Cookie A 3 Killer B 4 Dipface C 5 Swamp D 6 Donkey E 7 Wooly F 8 Weasel H G 10 9 J I Column 2 Column 3
- 12. Data Architecture How do you use your data? • Read paoern? – RelaBonal, object, CQRS (Query SegregaBon), Bme series, event sourcing, map reduce, full table scans – OperaBonal, offline and realBme – the three scopes of data analysis • Write paoern? – OperaBonal, ETLs, data imports • Search paoern? – By field filters, full text search, links (between items), relaBons • Data Mutability – Is your data mutable (e.g. update & delete operaBons)?
- 13. ConsideraBons for Data Architecture • CP vs AP – Consistency vs Availability – CAP theorem mandates you cannot get both (unless you allow split brain…) – CRDTs -‐ CommutaBve (or Conflict free) Replicated Data Types • Eventual Consistency – Can you model your system to cope with a certain level of inconsistency? • Performance vs Size vs Features – OpBmize for fast reads / fast writes / huge size / complex queries & MR • DRP – What happens if your engine dies? – What happens if your data get poisoned?
- 14. Build Architecture It’s about how you Build your code Build ConsideraBons • Dependencies – Code, Jar, Build, TesBng & Deployment dependencies • Build pipeline – Building dependencies in order – Building against the right dependencies • Minimize building and tesBng Bme • Version management – Major.minor.build.patch.fix.test…. – Do we need versions at all?
- 15. Build Architecture Dependencies • The root of all evil – reuse – Dependencies are introduced because component A uses component B – Without reuse, there are no dependencies • Diamond problem – Manual dependency progression (Maven, Ivy) – AutomaBc dependency progression (conBnuous delivery) – “Pick your poison” dependency progression (NPM) • Dependencies complexity – Complexity is an exponenBal funcBon of the number of components D C B A 1.1 A 1.0
- 16. Build Architecture It’s about how you Deploy your code • Deployment – Decoupling deployment from feature release – Automated deployment – Zero-‐downBme deployment • Rolling updates, parallel clusters (Netlix) – MulBple-‐environment support • Development, Debugging, TesBng, Staging, ProducBon • Post-‐Deployment – A/B tests – Feature Toggles – Immune system • Startup tests, post deployment monitoring – Automated rollback
- 17. What about Code Level Architecture? I do not believe there is “code-‐level architecture” • Coding is Engineering – WriBng modular code, maintainable code, testable code – Design paoerns are a theoreBcal tool • Architecture is about real-‐worlds constraints – In an ideal world – infinite space, infinite performance, infinite consistency magic database – do we need architecture? • Coding by itself is in a mathemaBcal exercise, in a theoreBcal domain. – Only when introducing “real-‐world” constraints do we need architecture
- 18. The Architect Role Architect Architecture !=
- 19. Anyone can do architecture
- 20. Everyone should do architecture
- 21. So what is the role of the Architect?
- 22. Lets consider a product A Hotel Management system Frontend UI Hotel & Room Management ReservaBons Checkout Backoffice UI Frontend Server MySQL ElasBc Search Payment Provider
- 23. The teams Frontend UI Backoffice UI Frontend Server Hotel & Room Management ElasBc Search ReservaBons Checkout MySQL Payment Provider A-Team Team B Team C
- 24. And a Feature Search for available rooms • Query the Hotel & Room Management service for the rooms that fit the search – By hotel star raBng, review score, etc. • Query the ReservaBon service to find available rooms – By availability of rooms, based on current reservaBons
- 25. The Hotel Search Feature? Frontend UI Backoffice UI Frontend Server Hotel & Room Management ElasBc Search ReservaBons Checkout MySQL Payment Provider A-Team Team B Team C Are you real??? 1. Frontend calls Hotels & Rooms Man. for the search, gets back a few pages of rooms. 2. Then, it calls ReservaBons with the results to filter out unavailable rooms
- 26. The Hotel Search Feature? Frontend UI Backoffice UI Frontend Server Hotel & Room Management ElasBc Search ReservaBons Checkout MySQL Payment Provider A-Team Team B Team C No Hacks Here! 1. Frontend calls Hotels & Rooms Man. for the search 2. Hotels & Rooms Man. searches for the right rooms 3. Then, it calls ReservaBons with the results to filter out unavailable rooms
- 27. What is a Hack?
- 28. What is a Hack? • Wikipedia – Hack is a soluBon to a problem, doing a task, or fixing a system that is inefficient, inelegant, or even unfathomable, but which nevertheless (more or less) works • What team C considers a hack – The idea that the search service calls the inventory service with the found rooms to check availability, merges the response and filters the results
- 29. The Hotel Search Feature? Frontend UI Backoffice UI Frontend Server Hotel & Room Management ElasBc Search ReservaBons Checkout MySQL Payment Provider A-Team Team B Team C 1. Frontend calls ReservaBons for the search 2. ReservaBons finds all available rooms on the specified dates 3. Then, it calls Hotels & Room Man. to filter and sort by the available rooms
- 30. The Architect Role • Did we define the right services? – Should the Hotel & Rooms Management and the ReservaBons Service be separate services? • Did we define the right teams? – Can the problem between the two services be caused because those are owned by two different teams? • IdenBfy the “hacks” – Teams tend to resist doing what they perceive as hacks – Each team tries to force the hacks out of their domain, turning hacks into integra4on problems – Which hacks are real hacks (we don’t want those) – Which hack are redefini4ons of parts (we want those)
- 31. The Architect Role Assuming we have the right teams and services • Help the teams select a soluBon – Using the architecture consideraBons we talked about • Redefine the services – A Service is defined by the use-‐cases it supports • And not by some theoreBcal idea of the team – If a Service needs to support search by doing another hackish request to another service – it is not a hack, but rather a redefini4on of the service • Beware, this statement does not mean a team should accept any hack!
- 32. The Architect Role The Architect role is to connect the Micro vs Macro Macro – whole product / company / soluBon • Business Requirements – Are we building the right product? What do want to get out of it? – Evolve with the business • Product DefiniBon – Assess features starBng with user stories and screen mockups • Real-‐world constraints – All the consideraBons we talked about The Architect role is to help teams sort the right path between requirement and constraints
- 33. The Architect Role The Architect role is to connect the Micro vs Macro Micro – one part / component / team • A Component should do one well defined thing – Handles one specific role – Does the team understand the role? • Coherence – Is the part / component well defined? • The role is defined by the requirements of the whole The Architect role is to help the team understand their part in the whole
- 34. The Architect Role Connect the Micro and the Macro • All for One and One for All – Teams and Components should support the business – Align the teams as part of the whole • Challenge the teams – Their architecture – Their part in the whole architecture
- 35. The Architecture Process Business Requirements Product DefiniBon Compile End 2 End Feature Flows DecomposiBon to teams & components Redefine Component Boundaries Architect facilitates the process Teams do the architecture • RunBme • Data • Build Real-‐World Constraints How teams & components collaborate to build the end-‐2-‐end product
- 37. My SoluBon Broaden the scope and allow some inconsistency • Reflect the room availability in the search service – We store availability twice (in reservaBons and search) – may get our of sync – Have the reservaBon service update the search on room orders • Handle the inconsistency – On opening a room page, or on ordering a page, we need to recheck the room availability What do we gain? • Simpler search flow – Search is used more compared to ordering – should be simpler • More robust system – Using async updates decouples failure and dependencies
- 38. ReservaBons Checkout MySQL Payment Provider My SoluBon -‐ Order Frontend UI Backoffice UI Frontend Server Hotel & Room Management ElasBc Search A-Team Team B Team C Order Are you insane? 1. On ReservaBon, ReservaBons noBfy Hotel & Room Man. • Async, low priority 2. Hotel & Room Man. stores inventory per room – We lose consistency!!! Me? Inventory?
- 39. My SoluBon -‐ Search Frontend UI Backoffice UI Frontend Server Hotel & Room Management ElasBc Search ReservaBons Checkout MySQL Payment Provider A-Team Team B Team C Search 1. Search is done with the Hotel & Room Management system, including room availability – Result may be inconsistent
- 40. My SoluBon – Showing Room Page Frontend UI Backoffice UI Frontend Server Hotel & Room Management ElasBc Search ReservaBons Checkout MySQL Payment Provider A-Team Team B Team C 1. Because we have a potenBally inconsistent state, as a user views a room page, we have to recheck availability Recheck availability It’s not our job!