[SpringOne2016] Developing Microservices with Aggregates

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%FWFMPQJOH.JDSPTFSWJDFT  XJUI"HHSFHBUFT d4QSJOH0OF1MBUGPSNใࠂձ ೔ຊ+BWBϢʔβʔάϧʔϓ  "DSPRVFTU5FDIOPMPHZגࣜձࣾ ୩ຊ৺ !DFSP@U

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ࣗݾ঺հ ͖ͬ͞͠·ͨ͠

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๻ͷதͰͷ  4QSJOH0OF  ϕετηογϣϯ

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-FUT7JTVBMJ[F:PVS  4QSJOH#PPU"QQMJDBUJPOT Acroquest Technology Co., LTD.  Shin Tanimoto (@cero_t)

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͡Όͳͯ͘

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@crichardson Developing Microservices with Aggregates Chris Richardson Founder of Eventuate.io Founder of the original CloudFoundry.com Author of POJOs in Action @crichardson [email protected] http://eventuate.io

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ϚΠΫϩαʔϏεΛ  %%%ͷυϝΠϯ୯ҐͰ  ࡞Δ΂͖ͩͱ͔  τϥϯβΫγϣϯͲ͏͢Δ  ͱ͔ͷ࿩

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Ωʔϫʔυ    %%%  Πϕϯτιʔγϯά  $234

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Α͘෼͔Βͳ͔ͬͨΜͰ  ؼࠃ͔ͯ͠Β΋ؚΊͯ  ϲ݄͙Β͍ߟ͑ଓ͚ͯΔ

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@crichardson Microservice architecture Browser Mobile Device Store Front UI API Gateway Catalog Service Review Service Order Service … Service Catalog Database Review Database Order Database … Database HTML REST REST Apply X-axis and Z-axis scaling to each service independently

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%#Λ෼͚ͪΌͬͨΒ ෳ਺υϝΠϯͷࢀরͬͯ  Ͳ͏΍Ε͹͍͍ͷʁ

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@crichardson Product service Customer service Order service Domain model = tangled web of classes Order OrderLine Item quantity … Address street city … Customer Product name price ? ? creditLimit

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@crichardson But it violates encapsulation… BEGIN TRANSACTION … SELECT ORDER_TOTAL FROM ORDERS WHERE CUSTOMER_ID = ? … SELECT CREDIT_LIMIT FROM CUSTOMERS WHERE CUSTOMER_ID = ? … INSERT INTO ORDERS … … COMMIT TRANSACTION Private to the Order Service Private to the Customer Service

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@crichardson 2PC is not a viable option Guarantees consistency BUT 2PC is best avoided Not supported by many NoSQL databases etc. CAP theorem 㱺 2PC impacts availability ….

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1$ͬͯදݱ  ΧοίΠΠ

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͡Όͳͯ͘

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1$͸  ͜ͷઌੜ͖ͷ͜Δ  બ୒ࢶͰ͸ͳ͍

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@crichardson 2PC is not a viable option Guarantees consistency BUT 2PC is best avoided Not supported by many NoSQL databases etc. CAP theorem 㱺 2PC impacts availability ….

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@crichardson Aggregate rule #2 Transaction = processing one command by one aggregate

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ճͷϚΠΫϩαʔϏείʔϧ τϥϯβΫγϣϯൣғ /P42-ͷτϥϯβΫγϣϯ

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@crichardson Aggregate granularity If an update must be atomic then it must be handled by a single aggregate Therefore Aggregate granularity is important

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ͦΜͳ͜ͱ͸  ෼͔ͬͯΔ

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@crichardson Aggregate granularity Consistency Scalability/ User experience Customer Order Product Customer Order Product Customer Order Product

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͔ͩΒɺͲ͏͢Δͷʁ

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@crichardson Customer management How to maintain data consistency between aggregates? Order management Order Service placeOrder() Customer Service updateCreditLimit() Customer creditLimit ... has orders belongs to Order total Invariant: sum(open order.total) <= customer.creditLimit ?

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@crichardson Use event-driven, eventually consistent order processing Order Service Customer Service Order created Credit Reserved Credit Check Failed Create Order OR Customer creditLimit creditReservations ... Order state total … create() reserveCredit() approve()/reject()

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ΠϕϯτυϦϒϯΛ༻͍ͨ  ݁Ռ੔߹ੑ

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ΦʔμʔαʔϏεͰΦʔμʔ࡞੒  ˣ  ܾࡁαʔϏεͰܾࡁ࡞੒  ˣ  ΦʔμʔαʔϏεͰॲཧܧଓ

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ͳΔ΄Ͳɺ෼͔Βͳ͘͸ͳ͍

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͋ΕɺͰ΋

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@crichardson How atomically update database and publish an event Order Service Order Database Message Broker insert Order publish OrderCreatedEvent dual write problem ?

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@crichardson 2PC is not an option

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Πϕϯτιʔγϯά

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@crichardson Event sourcing = event-centric persistence Application Database Event store update publish X

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%#Λߋ৽͢ΔͷͰ͸ͳ͍ɺ  ΠϕϯτΛอଘ͢ΔΜͩɻ

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@crichardson Persists events NOT current state Event table Entity type Event id Entity id Event data Order 902 101 … OrderApproved Order 903 101 … OrderShipped Event type Order 901 101 … OrderCreated

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@crichardson The present is a fold over history currentState = foldl(applyEvent, initialState, events)

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ۃ୺ʹݴ͑͹  ʮ͜ΕΛߪೖͨ͠ʯ͍ͬͯ͏  Πϕϯτ͚ͩอଘ͓͚ͯ͠͹  ͋ͱͷঢ়ଶ͸͔ͦ͜Βશ෦  ܭࢉͰ͖ΔΑͶɺͬͯ࿩ɻ

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͔͜͜Βઌͷηογϣϯ͸  ͍·ͩʹཧղͰ͖ͳ͍ͷͰ  ཧղͨ͠ͱ͜Ζ·Ͱͷ࿩ɻ

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ہॴతͳΠϕϯτιʔγϯά͸  ͔֬ʹ੒Γཱͭ

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γϣοϐϯάΧʔτ

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.&5"-3&4*45"/$&௥Ճ  50,:0%0.&.&.03*"-5&&௥Ճ #"#:.&5"-དྷ೔ه೦൫௥Ճ  #"#:.&5"-དྷ೔ه೦൫࡟আ  ˣ .&5"-3&4*45"/$&  50,:0%0.&.&.03*"-5&& #"#:.&5"-དྷ೔ه೦൫

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ॱ൪͸ؔ܎ͳ͘  ݁Ռ੔߹ੑϕʔεͰߟ͑Δ

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#"#:.&5"-དྷ೔ه೦൫࡟আ  #"#:.&5"-དྷ೔ه೦൫௥Ճ  ˣ #"#:.&5"-དྷ೔ه೦൫   #"#:.&5"-དྷ೔ه೦൫

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݁Ռ੔߹ͩͱͯ͠΋ɺ  Ͳ͏ू໿͢Δ͔͸ϙϦγʔ࣍ୈɻ    γϣοϐϯάΧʔτͰ͋Ε͹  ʮ࠷ऴతͳঢ়ଶʯΛ  Ϣʔβʹ֬ೝ͢Δ͜ͱ͕ඞਢ

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ݫີ͕͔ܽͤ͞ͳ͍ͳΒ  "$*%ͳ3%#.4Λ࢖͏͔͠ͳ͍

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ԁೖۚ  ԁҾग़  ԁҾग़ ˣ ͍΍͍΍ɺԁҾ͖ग़͢ॴͰ  /(Ͱ͠ΐ

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ԁೖۚ  ԁҾग़  ԁҾग़ ˣ ࢒ߴԁ

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Πϕϯτιʔγϯά೴Ͱߟ͑  ͦͷ௨Γʹۀ຿ཁ݅ΛدͤΔ    Ͳ͏ͯ͠΋μϝͳॴ͚ͩ  3%#.4Λ࢖͏

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Πϕϯτιʔγϯά͸  εςʔτιʔγϯάʹൺ΂ͯ  $234Λ࣮ݱ͠΍͍͢

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$234  $PNNBOE  2VFSZ  3FTQPOTJCJMJUZ  4FHSFHBUJPO

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ճͷॲཧ͸  ߋ৽͔ݕࡧͷยํ͚ͩʹ͢Δ

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4&-&$5CBMBODF  '30.BDDPVOU  '0361%"5&  ˣ  61%"5&BDDPVOU  4&5CBMBODF

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*/4&35*/50CBMBODF@FWFOU  FWFOU BNPVOU   WBMVFT bXJUIESBX`

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݁Ռ੔߹ੑϕʔεͷ  /P42-ͱ΋૬ੑ͕ྑ͍

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ͪͳΈʹࢿྉʹ໭Δͱ

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@crichardson Request handling in an event sourced application HTTP Handler Event Store pastEvents = ﬁndEvents(entityId) Order new() applyEvents(pastEvents) newEvents = processCmd(someCmd) saveEvents(newEvents) (optimistic locking) Order Service applyEvents(newEvents)

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ͳΜͰBQQMZ&WFOUΛ  &WFOU4UPSFˠ0SEFS  ʹ͠ͳ͍ΜͩΖʁ

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@crichardson Event Store publishes events consumed by other services Event Store Event Subscriber subscribe(EventTypes) publish(event) publish(event) Customer update() Customer Service

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@crichardson Event Store publishes events consumed by other services Event Store Event Subscriber subscribe(EventTypes) publish(event) publish(event) CQRS View update() Service Xyz send notiﬁcations …

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@crichardson The Customer aggregate Money creditLimit Map creditReservations Customer List process(CreateCustomerCommand cmd) { … } List process(ReserveCreditCommand cmd) { … } … void apply(CustomerCreatedEvent anEvent) { … } void apply(CreditReservedEvent anEvent) { … } … State Behavior

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@crichardson Familiar concepts restructured class Customer { public void reserveCredit( orderId : String, amount : Money) { // verify // update state this.xyz = … } public List process( ReserveCreditCommand cmd) { // verify … return singletonList( new CreditReservedEvent(…); ) } public void apply( CreditReservedEvent event) { // update state this.xyz = event.xyz }

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@crichardson Customer command processing

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·ͱΊ

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υϝΠϯ͝ͱʹαʔϏεΛ෼͚Δ    ϚΠΫϩαʔϏεʹର͢ΔϦΫΤετ͸  ͦͷ··τϥϯβΫγϣϯʹͳΔ 1$͸΋͏࢖Θͳ͍

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ʮঢ়ଶʯΛߋ৽͠ͳ͍ ʮΠϕϯτʯΛ௥Ճ͢Δ ʮঢ়ଶʯ͸ʮΠϕϯτʯͷ  ஝ੵ͔Β൑அ͢Δ    ʢΠϕϯτιʔγϯά$234ʣ

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Πϕϯτιʔγϯά΍$234͸  /P42-ʢ݁Ռ੔߹ੑʣϕʔεͷ  ϚΠΫϩαʔϏεͷ։ൃʹ  ͔ܽͤͳ͍ߟ͑ํͱͳΔ

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Ұॹʹษڧ͍͖ͯ͠·͠ΐ͏ʂ