java MongoCursorNotFoundException查询失败，错误代码为5

Question

我们得到以下例外情况

com.mongodb.MongoCursorNotFoundException: Query failed with error code -5 and error message 'Cursor 43249415092 not found on server xx.xx.xx.xx:27017' 
        at com.mongodb.connection.GetMoreProtocol.receiveMessage(GetMoreProtocol.java:115)
        at com.mongodb.connection.GetMoreProtocol.execute(GetMoreProtocol.java:68)
        at com.mongodb.connection.GetMoreProtocol.execute(GetMoreProtocol.java:37)
        at com.mongodb.connection.DefaultServer$DefaultServerProtocolExecutor.execute(DefaultServer.java:155)
        at com.mongodb.connection.DefaultServerConnection.executeProtocol(DefaultServerConnection.java:219)
        at com.mongodb.connection.DefaultServerConnection.getMore(DefaultServerConnection.java:194)
        at com.mongodb.operation.QueryBatchCursor.getMore(QueryBatchCursor.java:197)
        at com.mongodb.operation.QueryBatchCursor.hasNext(QueryBatchCursor.java:93)
        at com.mongodb.MongoBatchCursorAdapter.hasNext(MongoBatchCursorAdapter.java:46)
        at com.mongodb.DBCursor.hasNext(DBCursor.java:152)

我们无法找到根本原因，因为我们很少遇到这种异常

We also observed that the application is unable to read from cursor but no exception is thrown.

在没有抛出异常的情况下，我们进行了线程转储，发现从mongo读取的线程处于可运行状态

java.lang.Thread.State: RUNNABLE
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.read(SocketInputStream.java:152)
        at java.net.SocketInputStream.read(SocketInputStream.java:122)
        at com.mongodb.connection.SocketStream.read(SocketStream.java:85)
        at com.mongodb.connection.InternalStreamConnection.receiveResponseBuffers(InternalStreamConnection.java:503)
        at com.mongodb.connection.InternalStreamConnection.receiveMessage(InternalStreamConnection.java:221)
        at com.mongodb.connection.UsageTrackingInternalConnection.receiveMessage(UsageTrackingInternalConnection.java:102)
        at com.mongodb.connection.DefaultConnectionPool$PooledConnection.receiveMessage(DefaultConnectionPool.java:416)
        at com.mongodb.connection.GetMoreProtocol.receiveMessage(GetMoreProtocol.java:112)
        at com.mongodb.connection.GetMoreProtocol.execute(GetMoreProtocol.java:68)
        at com.mongodb.connection.GetMoreProtocol.execute(GetMoreProtocol.java:37)
        at com.mongodb.connection.DefaultServer$DefaultServerProtocolExecutor.execute(DefaultServer.java:155)
        at com.mongodb.connection.DefaultServerConnection.executeProtocol(DefaultServerConnection.java:219)
        at com.mongodb.connection.DefaultServerConnection.getMore(DefaultServerConnection.java:194)
        at com.mongodb.operation.QueryBatchCursor.getMore(QueryBatchCursor.java:197)
        at com.mongodb.operation.QueryBatchCursor.hasNext(QueryBatchCursor.java:93)
        at com.mongodb.MongoBatchCursorAdapter.hasNext(MongoBatchCursorAdapter.java:46)
        at com.mongodb.DBCursor.hasNext(DBCursor.java:152)

请帮助我找到这个问题的根本原因

Answer 1

最近，我遇到了同样的问题。经过长时间的研究，我找到了答案。在我的场景中，我有4个mongos，它们在负载平衡之后（随机返回mongos IP地址）。在我的连接字符串中，我使用负载平衡主机作为mongoDB集群的地址

当应用程序启动时，mongoDB驱动程序会创建一个带有连接池的server。在连接池中，有来自4个mongos的混合连接

当您查询一个大数据（比batchSize大）时，第一批数据来自mongos a，然后当推送下一批请求时，连接可能会连接到mongos B/C或D（source code）。他们当然找不到光标。因此，抛出MongoCursorNotFoundException

怎么处理

不要在连接字符串中使用平衡主机。改用所有mongos IP地址。让mongoDB驱动程序自己来平衡请求

错了：mongodb://your.load.balance.host:27000/yourDB?connectTimeoutMS=60000&minPoolSize=100&maxPoolSize=100&waitqueuemultiple=20&waitqueuetimeoutms=60000

右：mongodb://10.0.0.1:27017,10.0.0.2:27017,10.0.0.3:27017,10.0.0.4:27017/yourDB?connectTimeoutMS=60000&minPoolSize=100&maxPoolSize=100&waitqueuemultiple=20&waitqueuetimeoutms=60000

有一个更好的解决方案：您可以为每个mongos配置一个唯一的专用主机，然后修改右侧的连接字符串：用该主机替换IP地址