MongoDB-事务

mongoDB 执行事务，需要mongodb的集群模式，需要搭建一个mongo集群

1. docker搭建伪集群

如果需要支持mongo的事务，需要集群模式，这里搭建一个简单的伪集群做事务测试

  • 编写配置文件
  • vim /dockerData/mongo/config/mongod.conf
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# mongod.conf

# for documentation of all options, see:
#   http://docs.mongodb.org/manual/reference/configuration-options/

# Where and how to store data.
storage:
  dbPath: /data/db
  journal:
    enabled: true
#  engine:
#  mmapv1:
#  wiredTiger:

# where to write logging data.
systemLog:
  destination: file
  logAppend: true
  path: /var/log/mongodb/mongod.log

# network interfaces
net:
  port: 27017
#  bindIp: 127.0.0.1
  bindIpAll: true

# how the process runs
processManagement:
  timeZoneInfo: /usr/share/zoneinfo

#security:
#  authorization: enabled
#  keyFile: /etc/mongo/keyFilers0.key

#operationProfiling:

replication:
  oplogSizeMB: 150
  replSetName: itdeve-mongodb
sharding:
  clusterRole: shardsvr

## Enterprise-Only Options:

#auditLog:

#snmp:
  • 执行docker命令
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docker run -d --name mongo -p 27017:27017 \
-v /dockerData/mongo/data/db:/data/db \
-v /dockerData/mongo/config/mongod.conf:/etc/mongo/mongod.conf \
mongo:4.4.5 --config /etc/mongo/mongod.conf

  • 进去容器：docker exec -it mongo /bin/bash

  • 打开mongo命令行 mongo

  • 依次执行命令

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use admin
rs.initiate()
rs.conf()
exit
  • 伪集群搭建完成，可以测试事务

2. 添加事务支持

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@Configuration
public class MongoConfig {

    @Bean
    public MongoTransactionManager mongoTransactionManager(MongoDatabaseFactory mongoDatabaseFactory) {
        return new MongoTransactionManager(mongoDatabaseFactory);
    }
}
  • 接下来只需要再service方法上添加@Transactional注解即可

3. mysql与mongo事务冲突

如果项目中同时使用了mysql和mongo，并且都使用的事务，会导致mysql的事务失效，无法回滚。因为都实现了PlatformTransactionManager，springboot容器只会加载一个，所需如果需要同时加载两个PlatformTransactionManager的bean。需要对bean从命名，并且保证mysql事务方式不变，指定mysql事务为主

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package cn.aacopy.learn.mongo.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.data.mongodb.MongoDatabaseFactory;
import org.springframework.data.mongodb.MongoTransactionManager;
import org.springframework.jdbc.support.JdbcTransactionManager;

import javax.sql.DataSource;

/**
 * @author cmyang
 * @date 2022/11/20 0:57
 */
@Configuration
public class MongoConfig {

    @Bean("mongoTransactionManager")
    public MongoTransactionManager mongoTransactionManager(MongoDatabaseFactory mongoDatabaseFactory) {
        return new MongoTransactionManager(mongoDatabaseFactory);
    }

    @Bean("jdbcTransactionManager")
    @Primary
    public JdbcTransactionManager jdbcTransactionManager(DataSource dataSource) {
        return new JdbcTransactionManager(dataSource);
    }
}

  • mysql的事务还是保持原来的使用方式
  • mongodb在添加@Transactional注解时，需要指定PlatformTransactionManager 的具体bean名称
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@Service
public class TestAServiceImpl implements TestAService {

    @Autowired
    private TestARepository testARepository;

    @Transactional("mongoTransactionManager")
    public TestADO saveTestA() {
        TestADO testADO = new TestADO();
        testADO.setName("嘎嘎");
        testARepository.save(testADO);
        int i = 1/0;
        return testADO;
    }
}
  • 这样就解决了同时支持mysql和mongo事务的问题

4. 并发报错WriteConflict

mongo本身不支持事务，直接使用事务注解在并发情况下会报错WriteConflict。

官方提供的方案是，通过重试的方式spring-retry，但这种方式，很影响效率，

  • 添加依赖
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<dependency>
  <groupId>org.springframework.retry</groupId>
  <artifactId>spring-retry</artifactId>
</dependency>
  • 启动类上添加@EnableRetry
  • 编写自定义mongo事务注解@MongoTransactional
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@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Retryable(value = UncategorizedMongoDbException.class, exceptionExpression = "#{message.contains('WriteConflict error')}", maxAttempts = 128, backoff = @Backoff(delay = 500))
@Transactional(propagation = Propagation.REQUIRES_NEW, rollbackFor = Exception.class, timeout = 120)
public @interface MongoTransactional {

}
  • 使用自定义注解
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@MongoTransactional
public save(User user) {

}