前言:业务需要导入一百万条数据,for循环开启协程(线程)操作 业务时 ,出现了这个错误
The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:174)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:64)
at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:835)
at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:455)
at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240)
at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:199)
at java.sql.DriverManager.getConnection(DriverManager.java:664)
at java.sql.DriverManager.getConnection(DriverManager.java:247)
at com.cloudinward.base.db.MysqlDo.getConnection(MysqlDo.kt:22)
at com.cloudinward.base.mybatis.MybatisUtilKt$doMapperTra$2.invokeSuspend(MybatisUtil.kt:89)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
at kotlinx.coroutines.DispatchedTask.run(Dispatched.kt:238)
at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:594)
at kotlinx.coroutines.scheduling.CoroutineScheduler.access$runSafely(CoroutineScheduler.kt:60)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:742)
Caused by: com.mysql.cj.exceptions.CJCommunicationsException: Communications link failure
出现这个问题是因为超过了数据库最大连接数3000.
我想到用一个数据库连接去操作整个业务时,又出现了这个错误
Cause: org.apache.ibatis.executor.ExecutorException: Executor was closed.
这个问题是为什么呢?高并发操作,当其中一个线程拿到了数据库的连接,它会一直霸占这个连接直到它完成整个业务,那么再它执行整个流程时,其他线程没有数据库的连接就会报这个错了。
这个时候老大告诉我要用限流操作完成这个
可以看看这个链接,什么是限流。
kotlin语言:
fun main(args: Array<String>){
val limiter= RateLimiter.create(2.0)//一秒限制两个个
for (item in 1..3000) {
limiter.acquire() // 请求RateLimiter, 超过permits会被阻塞
GlobalScope.launch {
print("##############"+item)
}
}
}
Java语言:
public static void main(String[] args) {public static void testRateLimiter() { ListeningExecutorService executorService = MoreExecutors .listeningDecorator(Executors.newFixedThreadPool(5)); RateLimiter limiter = RateLimiter.create(4); // 每秒不超过4个任务被提交 for (int i = 0; i < 50; i++) { limiter.acquire(); // 请求RateLimiter, 超过permits会被阻塞 //executorService.submit(new Task3("is "+ i)); } } }class Task3 implements Runnable{ String str; public Task3(String str){ this.str = str; } @Override public void run() { System.out.println("Task2 call execute.." + str); } }