Patterns and practices for real-world event-driven microservices by Rachel Reese at Codemotion Dubai
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The document discusses the implementation and benefits of event-driven microservices at Jet.com, detailing the company's growth and technology stack. It emphasizes the importance of event sourcing, reactive programming, and functional programming principles, particularly using F#. The document also outlines specific patterns and practices for developing microservices, including guidelines on isolating side effects and ensuring scalability and reliability.
![The F# solution offers us an order of magnitude
increase in productivity and allows one developer to
perform the work [of] a team of dedicated
developers…
Yan Cui
Lead Server Engineer, Gamesys
“
“ “](https://image.slidesharecdn.com/pp-microservices-dubai-160410092239/85/Patterns-and-practices-for-real-world-event-driven-microservices-by-Rachel-Reese-at-Codemotion-Dubai-19-320.jpg)
![F# way 33
type Year = int
type [<Measure>] percent
type Customer = Simple | Valuable | MostValuable
type AccountStatus =
| Registered of Customer * since:Year
| Unregistered
let customerDiscount = function
| Simple -> 1<percent>
| Valuable -> 3<percent>
| MostValuable -> 5<percent>
let yearsDiscount = function
| years when years > 5 -> 5<percent>
| years -> 1<percent> * years
let accountDiscount = function
| Registered (customer, years) ->
customerDiscount customer, yearsDiscount years
| Unregistered -> 0<percent>, 0<percent>
let asPercent p = decimal p / 100m
let reducePriceBy discount price =
price - price * (asPercent discount)
let calculateDiscountedPrice price account =
let custDiscount, yrsDiscount =
accountDiscount account
price
|> reducePriceBy custDiscount
|> reducePriceBy yrsDiscount](https://image.slidesharecdn.com/pp-microservices-dubai-160410092239/85/Patterns-and-practices-for-real-world-event-driven-microservices-by-Rachel-Reese-at-Codemotion-Dubai-32-320.jpg)
Patterns and practices for real-world event-driven microservices by Rachel Reese at Codemotion Dubai
- 1. Rachel Reese Jet.com @rachelreese @JetTechnology Patterns and Practices for Real-world Event-driven Microservices
- 2. Real-world
- 3. We plan to be the new Amazon.com Launched July 22, 2015 • Both Apple & Android named our app as one of their top 5 for 2015 • Over 20k orders per day • Over 10.5 million SKUs • #4 marketplace worldwide • 700 microservices We’re hiring! http://jet.com/about-us/working-at-jet
- 4. Azure Web sites Cloud services VMs Service bus queues Services bus topics Blob storage Table storage Queues Hadoop DNS Active directory SQL Azure R F# Paket FSharp.Data Chessie Unquote SQLProvider Python Deedle FAK E FSharp.Async React Node Angular SAS Storm Elastic Search Xamarin Microservices Consul Kafka PDW Splunk Redis SQL Puppet Jenkins Apache Hive EventStore
- 6. Microservices An application of the single responsibility principle at the service level. Has an input, produces an output. Easy scalability Independent releasability More even distribution of complexity Benefits “A class should have one, and only one, reason to change.”
- 7. Event-driven
- 8. Event-driven The focus of your application code is to react to events (single or a stream).
- 9. Events Any significant change in state that has happened in your domain • Past tense • Immutable • Contains only relevant data to transaction All events should be represented as verbs in the past tense such as CustomerRelocated, CargoShipped, or InventoryLossageRecorded. For those who speak French, it should be passé composé, they are things that have completed in the past. Greg Young
- 10. Event Consumer “Events” as the notification messages Event channelEvent Emitter
- 11. Microservice input should be treated as an Observable Events should be an Observable Event-driven is Reactive Does anyone here use Rx?
- 12. Event-sourced
- 13. Compare to relational model which captures only the latest state change. These sets are then related to each other. Event-sourced • Event-sourced is about how you model the domain. • An append-only sequence of events as data store. • Keep track of all state changes. • Can REPLAY these event streams.
- 14. Event Stream
- 15. How did Jet decide on microservices?
- 16. Why F#?
- 17. FP |> Programmers <3
- 19. The F# solution offers us an order of magnitude increase in productivity and allows one developer to perform the work [of] a team of dedicated developers… Yan Cui Lead Server Engineer, Gamesys “ “ “
- 20. Why F#? Expanded feature set
- 21. Expanded feature set: Option types
- 22. Why F#? Concise & powerful code
- 23. Concise & powerful code public abstract class Transport{ } public abstract class Car : Transport { public string Make { get; private set; } public string Model { get; private set; } public Car (string make, string model) { this.Make = make; this.Model = model; } } public abstract class Bus : Transport { public int Route { get; private set; } public Bus (int route) { this.Route = route; } } public class Bicycle: Transport { public Bicycle() { } } type Transport = | Car of Make:string * Model:string | Bus of Route:int | Bicycle C# F# Trivial to pattern match on!
- 25. Concise & powerful code public abstract class Transport{ } public abstract class Car : Transport { public string Make { get; private set; } public string Model { get; private set; } public Car (string make, string model) { this.Make = make; this.Model = model; } } public abstract class Bus : Transport { public int Route { get; private set; } public Bus (int route) { this.Route = route; } } public class Bicycle: Transport { public Bicycle() { } } type Transport = | Car of Make:string * Model:string | Bus of Route:int | Bicycle | Train of Line:int let getThereVia (transport:Transport) = match transport with | Car (make,model) -> ... | Bus route -> ... | Bicycle -> ... Warning FS0025: Incomplete pattern matches on this expression. For example, the value ’Train' may indicate a case not covered by the pattern(s) C# F#
- 28. type Booking = | Basic of Plane | Combo of Combo | FullPack of Plane * Hotel * Car and Plane = {Outbound: DateTime; Return: DateTime; Destination: Country} and Combo = | ``With Hotel`` of Plane * Hotel | ``With Car`` of Plane * Car and Hotel = {Arrival: DateTime; Departure: DateTime; Location: Country} and Car = {From: DateTime; To: DateTime; Location: Country} and Country = {Name: String; ``ISO 3166-1``: char*char}
- 30. Original code
- 32. F# way 33 type Year = int type [<Measure>] percent type Customer = Simple | Valuable | MostValuable type AccountStatus = | Registered of Customer * since:Year | Unregistered let customerDiscount = function | Simple -> 1<percent> | Valuable -> 3<percent> | MostValuable -> 5<percent> let yearsDiscount = function | years when years > 5 -> 5<percent> | years -> 1<percent> * years let accountDiscount = function | Registered (customer, years) -> customerDiscount customer, yearsDiscount years | Unregistered -> 0<percent>, 0<percent> let asPercent p = decimal p / 100m let reducePriceBy discount price = price - price * (asPercent discount) let calculateDiscountedPrice price account = let custDiscount, yrsDiscount = accountDiscount account price |> reducePriceBy custDiscount |> reducePriceBy yrsDiscount
- 33. Guidelines
- 34. Be functional! Prefer immutability Avoid state changes, side effects, and mutable data Use data in data out transformations Think about mapping inputs to outputs. Look at problems recursively Consider successively smaller chunks of the same problem Treat functions as unit of work Higher-order functions
- 35. Don’t abstract This one magical service could write to ALL of the following: …badly. Event store Nservice Bus MSMQ 0MQ SQL Server
- 36. Isolate side effects Submit order microservice Insert order to SQL microservice Send thank you email microservice Updates SQL Sends “Thank you for ordering” Email Updates SQL Sends “Thank you for ordering” Email
- 37. Use a backup service to replay events Service 1 runs in production as normal Backup service 1 replays events until up-to-date. Switch over. Instantly live with changes! Also stage a copy of any aggregate/data store until stream has completed replaying!
- 38. type Input = | Product of Product type Output = | ProductPriceNile of Product * decimal | ProductPriceCheckFailed of PriceCheckFailed let handle (input:Input) = async { return Some(ProductPriceNile({Sku="343434"; ProductId = 17; ProductDescription = "My amazing product"; CostPer=1.96M}, 3.96M)) } let interpret id output = match output with | Some (Output.ProductPriceNile (e, price)) -> async {()} // write to event store | Some (Output.ProductPriceCheckFailed e) -> async {()} // log failure | None -> async {{ }} // log failure let consume = EventStoreQueue.consume (decodeT Input.Product) handle interpret What do our services look like? Define inputs & outputs Define how input transforms to output Define what to do with output Read events, handle, & interpret
- 39. Microservices should not control own lifecycle Execution runtime Deployment Configuration Restarting Versioning Scaling Availability Grouping by subsystem Scheduling Input-output static analysis Dashboard Think IoC!
- 40. Torch YAML files torchVer: 2.0.0 subSystem: PriceCheck name: PriceCheck description: checks prices on nile ver: 0.0.1 autoStart: always compile: true ha: aa ##active-active. Could be ap for active-passive scriptPath: PriceCheckNilePriceCheckNile.fsx libPath: binrelease args: --jsonConfig=PriceCheckNile.json It used to mean “Yet Another Markup Language” but was backronymed to clarify its focus as data-oriented. YAML = “YAML Ain’t Markup Language”
- 41. Summary Don’t abstract Be functional Isolate side effects Use a backup service Use consistent formatting Use an outside product to control lifecycle
- 42. For more information 43 F# fsharp.org fsharpforfunandprofit.com Event sourcing http://www.infoq.com/news/2014/09/greg-young-event-sourcing https://www.youtube.com/watch?v=JHGkaShoyNs Microservices martinfowler.com microservices.io
- 43. Rachel Reese Jet.com @rachelreese @JetTechnology Patterns and Practices for Real-world Event-driven Microservices
Editor's Notes
- #4: 400-1000 microservices.
- #5: Right tool for the job company. Chaos testing is the right tool. Azure: Storage Q for At-least-once Svc bus for At-most-once, transactions, persistence, order guarantee and Kafka for event distribution 5-7 mins
- #7: More even distribution of complexity: easier to create & maintain services (very small amount of logic), harder to manage all services. Shift complexity from biz logic to infrastructure. Better than one giant monolithic solution with 25 projects!
- #10: Before moving on, let’s define events. -“Event” refers to both the event itself, as well as the notification message that’s passed to the rest of the system.
- #11: Considering events as notification messages. This is push-based notification..
- #12: Reactive manifesto: Responsive Message-driven Resilient Elastic Microservice input should treated as an Observable and event-sourced.
- #14: How many folks do event-sourcing now?
- #15: Account history or ledger. Can replay and adjust if needed. – if need a ref number for all transactions now. CAN CREATE THIS Found a bug. Ran out of sockets. Updated SQL schema. Re-indexing Elasticsearch.
- #16: Why microservices? F#: data in -> data out; inputs -> outputs. A function. A microservice = just a function that naturally maps to an f# script, with input/out via the network. Also, naming: Best practices = naming services after the function they perform. Bad: “sku service” , good: “import skus" No explicit meeting where we decided to do microservices, one day we just realized we had a bunch of microservices
- #17: Pattern #1.
- #21: Fewer bugs come from less code. Rewrote into prod in 6 weeks!!
- #22: More features that I’ll talk about tomorrow.
- #23: NullReferenceException can be obviated because of option types. Similar to nullable<int> but different because: Can be used on any type (strings, functions) When pattern matched on, forces you to consider None case Can use map, iter, etc. functions. Nestable: Option<Option<int>> is valid.
- #25: Option type is a simple discriminated union. Both are idiomatic. C# version still lacks structural equality. Would need to override equality, comparison, AND GetHashCode. Also not proper immutability because private set is still mutable. -- there should be no setter, and the backing field should be readonly. Pattern matching is like a switch statement, but WAY more powerful.
- #27: Option type is a simple discriminated union. Both are idiomatic. C# version still lacks structural equality (based on contents): that means overriding the equality implementation, the comparison implementation, AND GetHashCode. (generates a hash code from your object instance). Also not proper immutability because private set is still mutable. To get real immutability, there should be no setter, and the backing field should be readonly. Pattern matching is like a switch statement, but WAY more powerful.
- #29: Paul's team. BA asked for "notes from meeting", was actual code.
- #30: Look at the code a little closer
- #31: An article came out on CodeProject very recently. https://twitter.com/Functional_S/status/709457140021399552
- #33: 25 lines of code to 118 lines of code. Doesn’t even show tests. WTF WHY.
- #34: 31 lines of code.
- #36: Once inputs and outputs are defined, the service is just a series of transformations. Can compose or pipe the operations. Trivial to make concurrent, to scale. Will help Composing handlers and avoiding handler’s hell. Subscription and handlers should be defined as a series of functions, outside the Micro Service. Functional! Using Async.Seq OO Patterns: command pattern, visitor pattern are both just higher order functions. HO fns often can more easily express a complex work flow.
- #37: (no slide, but) IDEMPOTENCY.
- #38: Where you can’t avoid side effects, isolate them! Can’t replay this service easily if SQL schema changes or if you find a bug -- will resend all emails!
- #39: Aggregate = row in SQL table with latest aggregated info. Eg. Order shipped. Keep staged version of aggregated info until stream has **completed** replaying. Otherwise, you’re writing events to table. Might turn on, then turn off an account. (again, isolate side effects) If we change the SQL schema. Just replay events into new schema. Keep a second service around. Spin that one up to replay. Then switch over to it and live instant new schema.
- #40: Decode >> Handle >> interpret Allows one fun to be called to implement. Being functional allows composition here.
- #41: Use Docker, Consul, etc. We rolled our own because: We can deploy a new build in 30s (instead of 15-20 minutes for a cloud service.) Scaling should include adding a new VM with assorted relevant services (automatically).
- #42: Active/active — Traffic intended for the failed node is either passed onto an existing node or load balanced across the remaining nodes. This is usually only possible when the nodes use a homogeneous software configuration. Active/passive — Provides a fully redundant instance of each node, which is only brought online when its associated primary node fails.[1] This configuration typically requires the most extra hardware.
- #44: Greg Young videos.