seadt Shopee Financial Products GolangTCCseadt TCCseadt TCCseadt-SAGAseadtTCCSAGASAGATCCSAGA1. SAGASAGASagasSAGASAGASAGA1 SAGAT C SAGA/SAGASAGA1

seadt Shopee Financial Products Golang

TCCseadt TCCseadt TCCseadt-SAGA

seadtTCCSAGASAGATCCSAGA

1. SAGA

SAGASagasSAGASAGASAGA

1 SAGA

T C SAGA/SAGASAGA

1.1 SAGA-

TCCSAGAATseadtTCCTCCSAGA

TCC

SAGA

SAGASAGASAGASAGASAGASAGA

1.2 SAGA-

SAGASAGA

1.2.1

SAGADSLTCTCTCSAGA

2

1. SAGA
2. TMTCSAGA
3. TCDSLQuotaA
4. 3TCDSLQuotaASAGA
5. 3TCDSLPromotionB
6. 5TCDSLPromotionB4
7. 5SAGA

import seadtfunc BizFunc() {    sagaTxId := "BizTrans"    seadt.StartSAGATx(ctx, seadt_name, req_id)}

// DSL{    "seadt_name":"BizTrans",    "tx_seq":[        {            "sub_tx_id": "UseQuota",            "commit_method": "/Module_Name/UseQuota",            "callback_method": "/Module_Name/UnUseQuota",            "pre_step":"Start",            "next_step":"UseCoupon"        },        {            "sub_tx_id": "UseCoupon",            "commit_method": "/Module_Name/UseCoupon",            "callback_method": "/Module_Name/UnUseCoupon",            "pre_step":"UseQuota",            "next_step":"End"        }    ]}

• DSL
• /
• SAGA

• DSL
• DSL

DSL(domain-specific language)HTMLDSL

1.2.2

SAGASDKTMSAGATMSAGASAGATCSAGA

3

1. SAGA
2. QuotaA
3. 2TMTCTCQuotaASAGA
4. 2PromotionB
5. 4TMTCTCQuotaPromotionSAGA
6. 4SAGA

func BizTrans(ctx context.Context, userId, loanId, couponIdPrincipal string) {  saga.WithGlobalTransaction(ctx, func(ctx context.Context) {         //      biz.RefAccount().UseQuota(ctx, userId, loanId, Principal)     //      biz.RefPromotion().UseCoupon(ctx, userId, couponId)     // local db op     dao.ClFileAuthDAO().Insert(ctx, record)      }, &seadt_model.Option{         TimeOutSecond:   10,         TransactionName: "loan_apply",  })

seadt TCCTCC10/

• TC

-TC / SDK-TC

• SAGA
• SDK-TCTCTMRMSDK
• -TCTC

SDKTC

TCTCTCTCseadt TC

1.3

1.2SAGA

seadt-SAGA

seadt

SAGASAGA

seadtTC

2. seadt-SAGA

2.1

seadt-SAGA

4 seadt-SAGA

2.2

seadt-SAGA

5 seadt-SAGA

• TM TC
• RM
• RM
• TM
• ConfirmTC
• CancelTCCancel RM Unuse/

2.3

1.2.2

6

seadt-SAGAseadt-TCCseadt-SDK SAGA Compensate API pbForward Forward pb

// saga_manager.govar quotaUseProxySagaRef *saga.SagaResourceServiceProxyfunc init() {  quotaUseProxySagaRef = saga.RegisterSagaResourceService(new(QuotaUseSagaImpl))}func GetQuotaUseSagaRef() *saga.SagaResourceServiceProxy {  return quotaUseProxySagaRef}

// saga_resource_impl.gotype QuotaUseSagaImpl struct {}func (t *QuotaUseSagaImpl) Forward(ctx context.Context, payload interface{}) (bool, error) {  biz.UseQuota(ctx, payload)   return true,nil}func (t *QuotaUseSagaImpl) Compensate(ctx context.Context, payload interface{}) bool {  biz.UnUseQuota(ctx, payload)  return true}

// service.gofunc UseQuota(ctx context.Context, req *api.UseQuotaReq, resp *api.UseQuotaResp) error {  db.WithTransaction(ctx, func(ctx context.Context) {     resp, err := seadt.GetQuotaUseSagaRef().Forward(ctx, req)     if err != nil {        panic(err)     }  })  return nil}

2.4

TCCSAGA

7

8

SAGATCCSAGACommitCommitCommitted

SAGATCCSAGA: PreparedConfirmedCanceledConfirmedCanceled

TM RM

RM RM

SAGARollbackingConfirmedCanceledSAGACanceled

1. Rollbacking

SAGA

SAGA-TC

SAGASAGAseadt

-

SAGA

Backward crash recovery for parallel sagas is similar to that for sequential sagas. Within each process of the parallel saga, transactions are compensated for (or undone) in reverse order just as with sequential sagas. In addition all compensations in a child process must occur before any compensations for transactions in the parent that were executed before the child was created (forked). (Note that only transaction execution order within a process and fork and join information constrain the order of compensation. If T1 and T2 have executed in parallel processes and T2 has read data written by T1, compensating for T1 does not force us to compensate for T2 first.) : Hector Garcaa-Molrna, Kenneth Salem. SAGAS

9 SAGA

SAGA

Happened-before

In computer science, the happened-before relation (denoted: ->) is a relation between the result of two events, such that if one event should happen before another event, the result must reflect that, even if those events are in reality executed out of order (usually to optimize program flow). This involves ordering events based on the potential causal relationship of pairs of events in a concurrent system, especially asynchronous distributed systems. It was formulated by Leslie Lamport.

The happened-before relation is formally defined as the least strict partial order on events such that:

• If events a and b occur on the same process, a -> b if the occurrence of event a preceded the occurrence of event b.
• If event a is the sending of a message and event b is the reception of the message sent in event a, a -> b.
• If two events happen in different isolated processes (that do not exchange messages directly or indirectly via third-party processes), then the two processes are said to be concurrent, that is neither a -> b nor b -> a is true.

: Happened-before wiki

Happened-beforeHappened-before

Happened-before

SAGAHappened-before

1. -

TCDSLSAGAHappened-before

2. -

SAGASAGATCHappened-beforeHappened-before

Happened-before

Happened-before

VC n n

1. P i V C i = [ 0 , , 0 ]
2. P i i V C i [ i ] + = 1
3. P i P j V C i
4. P j [ 0 , n ) k V C j [ k ] = M a x ( V C j [ k ] , V C i [ k ] ) 2V C j [ j ] + = 1

1TM(Trans)RMQuotaPromotion

1. TransP0QuotaP1PromotionP2
2. TMRMVCi = [0,0,0]
3. TransATrans[1,0,0]
4. TransQuotaQuotaBQuota[2,1,0]
5. TransQuotaPromotionPromotionCPromotion[4.2,1]

10

TCTCABCHappened-beforeA[1,0,0] < B[2,1,0] < C[4.2,1] => A -> B -> C

Happened-before

PiHashMapKeyValue

11

Happened-before

SAGASAGA

12

seadtTCTC

2. ASeq-a < BSeq-bABABABASeq-a < BSeq-b

(TC)()SAGA

Happened-before

Happened-beforeseadtseadt-sdk

seadtseadt-sdkseadt-tc

1. sagahttps://github.com/mltds/sagas-report
2. https://zh.wikipedia.org/wiki/%E5%81%8F%E5%BA%8F%E5%85%B3%E7%B3%BB
3. https://zh.wikipedia.org/wiki/%E5%85%A8%E5%BA%8F%E5%85%B3%E7%B3%BB
4. Happened-beforehttps://en.wikipedia.org/wiki/Happened-before
5. https://writings.sh/post/logical-clocks
6. 
   

:Yongchang

::Shopee

:https://mp.weixin.qq.com/s/VGz3YIHPzkniCWNDsc8Xgw

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