带你用Python实现Saga 分布式事务的方法

CREATE TABLE dtm_busi.`user_account` ( 
  `id` int(11) AUTO_INCREMENT PRIMARY KEY, 
  `user_id` int(11) not NULL UNIQUE , 
  `balance` decimal(10,2) NOT NULL DEFAULT '0.00', 
  `create_time` datetime DEFAULT now(), 
  `update_time` datetime DEFAULT now() 
); 

def saga_adjust_balance(cursor, uid, amount): 
  affected = utils.sqlexec(cursor, "update dtm_busi.user_account set balance=balance+%d where user_id=%d and balance >= -%d" %(amount, uid, amount)) 
  if affected == 0: 
    raise Exception("update error, balance not enough") 

@app.post("/api/TransOutSaga") 
def trans_out_saga(): 
  saga_adjust_balance(c, out_uid, -30) 
  return {"dtm_result": "SUCCESS"} 
 
@app.post("/api/TransOutCompensate") 
def trans_out_compensate(): 
  saga_adjust_balance(c, out_uid, 30) 
  return {"dtm_result": "SUCCESS"} 
 
@app.post("/api/TransInSaga") 
def trans_in_saga(): 
  saga_adjust_balance(c, in_uid, 30) 
  return {"dtm_result": "SUCCESS"} 
 
@app.post("/api/TransInCompensate") 
def trans_in_compensate(): 
  saga_adjust_balance(c, in_uid, -30) 
  return {"dtm_result": "SUCCESS"} 

# 这是 dtm 服务地址 
dtm = "http://localhost:8080/api/dtmsvr" 
# 这是业务微服务地址 
svc = "http://localhost:5000/api" 
 
    req = {"amount": 30} 
    s = saga.Saga(dtm, utils.gen_gid(dtm)) 
    s.add(req, svc + "/TransOutSaga", svc + "/TransOutCompensate") 
    s.add(req, svc + "/TransInSaga", svc + "/TransInCompensate") 
    s.submit() 

# 部署启动 dtm 
# 需要 docker 版本 18 以上 
git clone https://github.com/yedf/dtm 
cd dtm 
docker-compose up 
 
# 另起一个命令行 
git clone https://github.com/yedf/dtmcli-py-sample 
cd dtmcli-py-sample 
pip3 install flask dtmcli requests 
flask run 
 
# 另起一个命令行 
curl localhost:5000/api/fireSaga 

@app.post("/api/TransOutSaga") 
def trans_out_saga(): 
  with barrier.AutoCursor(conn_new()) as cursor: 
    def busi_callback(c): 
      saga_adjust_balance(c, out_uid, -30) 
    barrier_from_req(request).call(cursor, busi_callback) 
  return {"dtm_result": "SUCCESS"} 

@app.post("/api/TransInSaga") 
def trans_in_saga(): 
  return {"dtm_result": "FAILURE"} 

@app.post("/api/TransInSaga") 
def trans_in_saga(): 
  with barrier.AutoCursor(conn_new()) as cursor: 
    def busi_callback(c): 
      saga_adjust_balance(c, in_uid, 30) 
    barrier_from_req(request).call(cursor, busi_callback) 
  return {"dtm_result": "FAILURE"}