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English | [简体中文](https://github.com/dtm-labs/dtm/blob/main/helper/README-cn.md)
# Distributed Transactions Manager
## What is DTM
DTM is a distributed transaction framework which provides cross-service eventual data consistency. It provides saga, tcc, xa, 2-phase message, outbox patterns for a variety of application scenarios. It also supports multiple languages and multiple store engine to form up a transaction as following:
## Features
## Who's using DTM (partial)
[Tencent](https://en.dtm.pub/other/using.html#tencent)
[Bytedance](https://en.dtm.pub/other/using.html#bytedance)
[Ivydad](https://en.dtm.pub/other/using.html#ivydad)
[More](https://en.dtm.pub/other/using.html)
## [Cook Book](https://en.dtm.pub)
## Quick start
### run dtm
``` bash
git clone https://github.com/dtm-labs/dtm && cd dtm
go run main.go
```
### Start an example
Suppose we want to perform an inter-bank transfer. The operations of transfer out (TransOut) and transfer in (TransIn) are coded in separate micro-services.
Here is an example to illustrate a solution of dtm to this problem:
``` bash
git clone https://github.com/dtm-labs/dtmcli-go-sample && cd dtmcli-go-sample
go run main.go
```
## Code
### Use
``` go
// business micro-service address
const qsBusi = "http://localhost:8081/api/busi_saga"
// The address where DtmServer serves DTM, which is a url
DtmServer := "http://localhost:36789/api/dtmsvr"
req := &gin.H{"amount": 30} // micro-service payload
// DtmServer is the address of DTM micro-service
saga := dtmcli.NewSaga(DtmServer, shortuuid.New()).
// add a TransOut subtraction，forward operation with url: qsBusi+"/TransOut", reverse compensation operation with url: qsBusi+"/TransOutCom"
Add(qsBusi+"/TransOut", qsBusi+"/TransOutCom", req).
// add a TransIn subtraction, forward operation with url: qsBusi+"/TransIn", reverse compensation operation with url: qsBusi+"/TransInCom"
Add(qsBusi+"/TransIn", qsBusi+"/TransInCom", req)
// submit the created saga transaction，dtm ensures all subtractions either complete or get revoked
err := saga.Submit()
```
When the above code runs, we can see in the console that services TransOut, TransIn has been called.
#### Timing diagram
A timing diagram for a successfully completed SAGA transaction would be as follows:
#### Rollback upon failure
If any forward operation fails, DTM invokes the corresponding compensating operation of each sub-transaction to roll back, after which the transaction is successfully rolled back.
Let's purposely fail the forward operation of the second sub-transaction and watch what happens
``` go
app.POST(qsBusiAPI+"/TransIn", func(c *gin.Context) {
log.Printf("TransIn")
// c.JSON(200, "")
c.JSON(409, "") // Status 409 for Failure. Won't be retried
})
```
The timing diagram for the intended failure is as follows:
## More examples
The above example mainly demonstrates the flow of a distributed transaction. More on this, including practical examples of how to interface with an actual database, how to do compensation, how to do rollback, etc. please refer to [dtm-examples](https://github.com/dtm-labs/dtm-examples) for more examples.
## Chat Group
Join the chat via [https://discord.gg/dV9jS5Rb33](https://discord.gg/dV9jS5Rb33).
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