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Making of SaaS Backend
guided by PofEAA
@dnskimox
PofEAAで考える
SaaSバックエンドの作り方
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Who am I
● Tanga Kenichi
● @dnskimox
● Backend Developer
● SaaS for contract management
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自己紹介
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PofEAA
The book about powerful
design patterns for
“Enterprise Application”
written by Martin Fowler
at 2002.
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邦題：エンタープライズアプリケーションアーキテクチャ
パターン
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What is the
“Enterprise application”?
Enterprise application does:
● store vary data
● manage huge data
● accept many requests at a time
● collaborate with other Enterprise
applications
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エンタープライズアプリケーションとは
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Enterprise Application ≒ Web Service
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Especially a web service requiring massive development
ほぼWEBサービスのこと
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A web service of this session’s subject is...
このセッションで取り上げる架空のWEBサービス
＊this service is fictitious
MakeInvoice
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Contents
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About MakeInvoice
The way we have managed such a
large, complex application
Architecture in MakeInvoice
Service description about
MakeInvoice, invoice creation and
management SaaS
Design patterns that will be
worthwhile to adopt to MakeInvoice
Adoptable Patterns
1
2
3
目次
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1. About MakeInvoice
Service description about
MakeInvoice, invoice
creation and management
SaaS
MakeInvoiceについて
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CloudSign
Salesforce
Dashboard(SPA)
Client Service
MakeInvoice
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Simple Domain Model
素朴なドメインモデル
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Slightly Complex Domain Model
やや複雑なドメインモデル
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More Complex Domain Model
さらに複雑なドメインモデル
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And More...
さらにさらに
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This logic has to consider:
● difference between regular and discount
item
● tax calculation
● to manipulate a template of document
Invoice Creation
請求書生成のビジネスロジック
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This logic has to consider:
● partial payment
● overpaying
● carrying over to next month
Reconciliation
入金消込のビジネスロジック
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This logic has to consider:
● resending invoice
● how to handling old invoice
● difference between total price and price
paid partially
Demand for Payment
支払催促のビジネスロジック
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Combine and Split Invoice
請求書の結合と分割のビジネスロジック
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Large domain model
structure
Complex business
logic
Requests from
dashboard, from
Salesforce, from
other services using
MakeInvoice
Some other SaaS to
have to connect
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Characteristics
of MakeInvoice
backend API
MakeInvoiceのバックエンドAPIの特徴
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2. Architecture in
MakeInvoice
The way we have managed
such a large, complex
application
MakeInvoiceのアーキテクチャ
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Clean Architecture
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Domain Layer
UseCase Layer
Primary / Secondary Adapter
Code for technical interest and implementation
i.e: Http, gRPC, RDB, KVS
Represents common use-cases using domain model
Contains only “pure” domain concepts and logic
Dependency
direction
各レイヤーの責務
依存の方向性
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Hexagonal architecture
This architecture aims to:
● receive request from
variety of clients
● reuse essential application
code
● write data on several data
storages or send to other
system
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https://blog.tai2.net/hexagonal_architexture.html
ヘキサゴナルアーキテクチャ
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Hexagonal architecture
● Primary Adapters are
adapters to communicate
with primary actor.
● Secondary Adapters are
adapters to communicate
with supporting actor (also
known as secondary
actor).
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https://blog.tai2.net/hexagonal_architexture.html
プライマリアダプターと主アクター
セカンダリアダプターと支援アクター
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3. Adoptable Patterns
Design patterns that will
be worthwhile to adopt to
MakeInvoice
適用可能なパターン
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Domain Layer
UseCase Layer
Primary / Secondary Adapter
DataMapper, SingleTableInheritance,
EmbeddedValue, SerializedLOB, DependentMapping,
DataTransferObject, ServiceStub
(Nothing)
DomainModel, POJO, ValueObject, Repository
レイヤー毎のパターン
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Representing domain model is
simple, unless domain classes
depend on any library or framework.
Domain Layer
ドメインレイヤー
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会社、顧客、書類、請求書、請求書品目
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“We wondered why people were
so against using regular objects
in their systems and concluded
that it was because simple
objects lacked a fancy name. ”
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https://martinfowler.com/bliki/POJO.html
Plain Old Java Object (POJO)
昔からある単なるJavaオブジェクト
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case class Invoice (
id: DocumentId,
companyId: CompanyId,
customerId: CustomerId,
items: Seq[InvoiceItem],
billingDate: LocalDate,
billingDueDate: LocalDate,
status: InvoiceStatus
) extends Document
abstract class Document {
val id: DocumentId
val companyId: CompanyId
val customerId: CustomerId
}
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“An object model of the domain
that incorporates both
behavior and data.”
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Domain Model
https://www.martinfowler.com/eaaCatalog/domainModel.html
ドメインモデル
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case class Invoice (
id: DocumentId,
companyId: CompanyId,
customerId: CustomerId,
items: Seq[InvoiceItem],
billingDate: LocalDate,
dueDate: LocalDate,
status: InvoiceStatus
) extends Document {
def totalPrice: Money = ???
def subtotal: Money = ???
def tax: Money = ???
def combine(other: Invoice): Invoice = ???
def split(prices: Seq[Money]): Seq[Invoice] = ???
}
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“A small simple object, like
money or a date range, whose
equality isn't based on
identity.”
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Value Object
https://www.martinfowler.com/eaaCatalog/valueObject.html
値オブジェクト
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case class Money(
currency: Currency,
value: BigDecimal
)
case class Currency(
currencyCode: String
)
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case class Money(
currency: Currency,
value: BigDecimal
) {
def plus(other: Money): Money = ???
def minus(other: Money): Money = ???
def mul(factor: BigDecimal): Money = ???
def div(factor: BigDecimal): Money = ???
}
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case class Address(
countryCode: CountryCode,
zipCode: ZipCode,
city: String,
address1: String,
address2: String
) {
def isSame(other: Address): Boolean = ???
}
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“Mediates between the domain
and data mapping layers using a
collection-like interface for
accessing domain objects.”
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https://www.martinfowler.com/eaaCatalog/repository.html
Repository
リポジトリ
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書類リポジトリ
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trait DocumentRepository {
def store[R :_trantask :_error](document: Document): Eff[R, Document]
def resolve[R :_trantask :_error](id: DocumentId): Eff[R, Document]
def matching[R :_trantask :_error](criteria: Criteria): Eff[R, Seq[Document]]
}
case class Criteria(
companyId: Option[CompanyId],
customerId: Option[CustomerId],
documentType: Option[DocumentType]
) {
def isSatisfiedBy(document: Document): Boolean = ???
}
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What is EFF?
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For more information, please go to Yoshimura‘s session.
EFFについて
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Design Domain Layer
from Domain Model
not from database.
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ドメインモデルから設計を始める
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otherwise
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さもないと
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“By pulling all the behavior out
into services, however, you
essentially end up with
Transaction Scripts, and thus lose
the advantages that the domain
model can bring. ”
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https://martinfowler.com/bliki/AnemicDomainModel.html
AnemicDomainModel
ドメインモデル貧血症
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This layer contains business
transaction only. So meaningful
patterns adopted here would be
honestly nothing.
UseCase Layer
ユースケースレイヤー
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class CreateDocumentUseCase @Inject() (
documentRepository: DocumentRepository,
documentFactory: DocumentFactory
) {
def execute[R :_trantask :_error](
documentType: DocumentType,
...
): Eff[R, Unit] =
for {
document <- documentFactory.create(documentType, ...)
_ <- documentRepository.store(document)
} yield ()
}
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Secondary Adapter
Main concern in this layer probably is
mapping objects to/from relational
database. Also clients to request to
external service is in this layer.
セカンダリアダプター
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“A layer of Mappers that moves
data between objects and a
database while keeping them
independent of each other and
the mapper itself.”
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https://www.martinfowler.com/eaaCatalog/dataMapper.html
Data Mapper
データマッパー
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“An object that sets up a
communication between two
independent objects.”
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https://www.martinfowler.com/eaaCatalog/mapper.html
Mapper
マッパー
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Table schema
is free
from domain model.
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テーブルスキーマは自由
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Separation of Concerns
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関心の分離
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class DocumentRepositoryImpl {
def store[R :_trantask :_error](document: Document): Eff[R, Document]
= ???
def resolve[R :_trantask :_error](id: DocumentId): Eff[R, Document]
= ???
def matching[R :_trantask :_error](criteria: Criteria): Eff[R, Seq[Document]]
= ???
}
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Impedance Mismatch
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Object Oriented World
● Abstraction
● Composition
Relational DB World
● Set
● Relation
インピーダンスミスマッチ
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Impedance Mismatch
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Object Oriented World
● Abstraction
● Composition
Relational DB World
● Set
● Relation
抽象化を集合と関係の世界へ
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抽象クラスの書類
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“Represents an inheritance
hierarchy of classes as a single
table that has columns for all the
fields of the various classes.”
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https://www.martinfowler.com/eaaCatalog/singleTableInheritance.html
Single Table Inheritance
シングルテーブル継承
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書類テーブル
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書類の種類を増やす
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書類テーブル Ver.2
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Many nullable fields!
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Nullを許容するフィールドがたくさん
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“Represents an inheritance
hierarchy of classes with one
table for each class.”
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https://www.martinfowler.com/eaaCatalog/classTableInheritance.html
Class Table Inheritance
クラステーブル継承
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書類テーブル Ver.3
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Impedance Mismatch
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Object Oriented World
● Abstraction
● Composition
Relational DB World
● Set
● Relation
コンポジションを集合と関係の世界へ
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顧客に含まれる名前オブジェクト
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“Maps an object into several
fields of another object's table.”
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https://www.martinfowler.com/eaaCatalog/embeddedValue.html
Embedded Value
組込バリュー
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顧客テーブル
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顧客に含まれる住所オブジェクト
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x 1?
顧客テーブル Ver.2
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“Saves a graph of objects by
serializing them into a single
large object (LOB), which it
stores in a database field.”
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https://www.martinfowler.com/eaaCatalog/serializedLOB.html
Serialized LOB
シリアライズドLOB
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x ∞
顧客テーブル Ver.3
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Not bad
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悪くない
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But...
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でも
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● Managing scheme is
difficult.
● Adding and removing
property is
problematic.
● Result of SQL is not
human friendly.
● Managing scheme is
almost unnecessary.
● New table is not
needed.
● Table joining does
not occur.
● Object count is
unlimited.
Using serialized field has pros and cons
Pros Cons
シリアライズされたフィールドの功罪
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“Has one class perform the
database mapping for a child
class.”
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https://www.martinfowler.com/eaaCatalog/dependentMapping.html
Dependent Mapping
依存マッピング
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x ∞
顧客テーブル Ver.4
Dependent Object
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● When owner object is
updated, dependent
objects are all
deleted then
re-inserted.
● When owner object is
deleted, dependent
objects are deleted
cascadingly.
● Any object except for
owner cannot
associate with
dependent object.
● Dependent object's
table has foreign key
for owner's table.
Dependent object's characteristic
Association/Relation Update/Delete
依存オブジェクトの特徴
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“Removes dependence upon
problematic services during
testing. WSDL ”
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https://www.martinfowler.com/eaaCatalog/dependentMapping.html
Service Stub
サービススタブ
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クラウドサインサービス
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Primary Adapter
This layer is so-called "Presentation
Layer". To parse request from client
and to compose response are its
responsibility. Also main App for
running batch program is contained
here.
プライマリアダプター
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“Provides a coarse-grained
facade on fine-grained objects to
improve efficiency over a
network.”
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https://www.martinfowler.com/eaaCatalog/remoteFacade.html
Remote Facade
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class DocumentController @Inject() (
createDocumentUseCase: CreateDocumentUseCase,
getDocumentUseCase: GetDocumentUseCase
) extends AkkaHttpController {
def routes: Route =
pathPrefix("DocumentService") {
post {
path("CreateDocument") { createDocument } ~
path("GetDocument") { getDocument }
}
}
private def createDocument: Route = ???
private def getDocument: Route = ???
}
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Split endpoints
moderately
coarse grained.
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荒い粒度でエンドポイントを分割する
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“An object that carries data
between processes in order to
reduce the number of method
calls.”
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https://www.martinfowler.com/eaaCatalog/dataTransferObject.html
Data Transfer Object
データ変換オブジェクト
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ドキュメントアセンブラ
ドキュメントDTO
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DTO structure
is free
from domain model.
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DTOの構造は自由
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Separation of Concerns
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関心の分離
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Domain Model
Repository
ValueObject
DataMapper
SingleTableInheritanse
ClassTableInheritanse
EmbededValue
SerializedLOB
DependentMapping
DTO
Remote
Facade
Putting It All Together
全てのパターンをひとつに
SPA
DB
UseCase
Service Stub
Other SaaS
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Conclusion
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PofEAA put forward many
useful patterns for complex
web application. But , as
Fowler writes, these patterns
have pros and cons. So we
have to keep thinking which
patterns to use or not use any
pattern.
Use this advice to prod your
thinking. In the end you have
to make, and live with, the
decisions yourself. One good
thing is that your decisions are
not cast forever in stone.
- Martin Fowler
結論
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Now, you have learned main
concept to write code of
backend.
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もうScalebaseのバックエンドを書けるはず
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Join us!
ご応募お待ちしております！
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Does anyone have any
questions?
@dnskimox
dnskimox.hateblo.jp
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Thanks!
ご清聴ありがとうございました！
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Reference literature
● https://www.amazon.co.jp/dp/B008OHVDFM
● https://www.martinfowler.com/eaaCatalog/index.html
● https://bliki-ja.github.io/pofeaa/CatalogOfPofEAA_Ja/
● https://martinfowler.com/bliki/POJO.html
● https://martinfowler.com/bliki/AnemicDomainModel.html
● https://blog.tai2.net/hexagonal_architexture.html
● http://atnos-org.github.io/eff/index.html
● https://github.com/google/guice
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参考文献