记一次spring boot中MongoDB Prematurely reached end of stream的异常解决

　　在spring boot项目中使用了mongodb，当一段时间没有操作mongodb，下次操作mongodb时就会出现异常。异常如下：

org.springframework.data.mongodb.UncategorizedMongoDbException: Prematurely reached end of stream; nested exception is com.mongodb.MongoSocketReadException: Prematurely reached end of stream
        at org.springframework.data.mongodb.core.MongoExceptionTranslator.translateExceptionIfPossible(MongoExceptionTranslator.java:107)
        at org.springframework.data.mongodb.core.MongoTemplate.potentiallyConvertRuntimeException(MongoTemplate.java:2146)
        at org.springframework.data.mongodb.core.MongoTemplate.executeFindOneInternal(MongoTemplate.java:1928)
        at org.springframework.data.mongodb.core.MongoTemplate.doFindOne(MongoTemplate.java:1736)
        at org.springframework.data.mongodb.core.MongoTemplate.findOne(MongoTemplate.java:606)
        at org.springframework.data.mongodb.core.MongoTemplate.findOne(MongoTemplate.java:601)
        at com.lwli.service.impl.SessionServiceImpl.findOneSessionByCustomerIdAndStatus(SessionServiceImpl.java:51)
        at java.lang.Thread.run(Thread.java:745)
Caused by: com.mongodb.MongoSocketReadException: Prematurely reached end of stream
        at com.mongodb.connection.SocketStream.read(SocketStream.java:88)
        at com.mongodb.connection.InternalStreamConnection.receiveResponseBuffers(InternalStreamConnection.java:494)
        at com.mongodb.connection.InternalStreamConnection.receiveMessage(InternalStreamConnection.java:224)
        at com.mongodb.connection.UsageTrackingInternalConnection.receiveMessage(UsageTrackingInternalConnection.java:96)
        at com.mongodb.connection.DefaultConnectionPool$PooledConnection.receiveMessage(DefaultConnectionPool.java:440)
        at com.mongodb.connection.QueryProtocol.execute(QueryProtocol.java:289)
        at com.mongodb.connection.QueryProtocol.execute(QueryProtocol.java:54)
        at com.mongodb.connection.DefaultServer$DefaultServerProtocolExecutor.execute(DefaultServer.java:168)
        at com.mongodb.connection.DefaultServerConnection.executeProtocol(DefaultServerConnection.java:289)
        at com.mongodb.connection.DefaultServerConnection.query(DefaultServerConnection.java:212)
        at com.mongodb.operation.FindOperation$1.call(FindOperation.java:525)
        at com.mongodb.operation.FindOperation$1.call(FindOperation.java:510)
        at com.mongodb.operation.OperationHelper.withConnectionSource(OperationHelper.java:435)
        at com.mongodb.operation.OperationHelper.withConnection(OperationHelper.java:408)
        at com.mongodb.operation.FindOperation.execute(FindOperation.java:510)
        at com.mongodb.operation.FindOperation.execute(FindOperation.java:81)
        at com.mongodb.Mongo.execute(Mongo.java:836)
        at com.mongodb.Mongo$2.execute(Mongo.java:823)
        at com.mongodb.DBCursor.initializeCursor(DBCursor.java:870)
        at com.mongodb.DBCursor.hasNext(DBCursor.java:142)
        at com.mongodb.DBCursor.one(DBCursor.java:679)
        at com.mongodb.DBCollection.findOne(DBCollection.java:833)
        at com.mongodb.DBCollection.findOne(DBCollection.java:796)
        at com.mongodb.DBCollection.findOne(DBCollection.java:743)
        at org.springframework.data.mongodb.core.MongoTemplate$FindOneCallback.doInCollection(MongoTemplate.java:2197)
        at org.springframework.data.mongodb.core.MongoTemplate$FindOneCallback.doInCollection(MongoTemplate.java:2181)
        at org.springframework.data.mongodb.core.MongoTemplate.executeFindOneInternal(MongoTemplate.java:1925)
        ... 12 more

　　网上搜了下，这个问题原因很多，主要的原因可能有连接超时，读写超时等，按照别人的提示，设置了

socketKeepAlive = true;

socketTimeout = 30000;

　　然而并没有效果，超过一段时间再次访问mongdb时，任然出现异常。在google搜索时，发现一篇文章https://studio3t.com/whats-new/how-to-prevent-your-connection-from-dropping-with-hosted-mongodb-instances/，上面提到了一点，当连接闲置一段时间，由于防火墙或者负载均衡的原因，导致连接被关闭，而客户端并不知道，当客户端继续使用这个关闭的连接进行读写时就会出错。

　　解决办法就是设置连接闲置时间，当超过这个闲置时间客户端主动关闭连接，下次使用时重新建立连接，这样可以有效避免连接失效的问题。

　　在spring boot中配置MongoClientOptions的bean。例如将最大闲置时间设为6000ms。

@Configuration
public class WechatMpConfiguration {

    @Bean
    public MongoClientOptions mongoOptions() {
        return MongoClientOptions.builder().maxConnectionIdleTime(6000).build();
    }
}

　　通过上面的设置后，后面没有再出现Prematurely reached end of stream异常了。