How to estimate the memory size of flink state

We are using flink 1.6.2. For filesystem backend, we want to monitor the state size in memory. Once the state size becomes bigger, we can get noticed and take measures such as rescaling the job, or the job may fail because of the memory. We have tried to get the memory usage for the jvm

?????? ??????savepoint???????????? migration for MapState currently isn't supported.

1.9.1??  Caused by: org.apache.flink.util.StateMigrationException: The new state serializer cannot be incompatible. --  

Re: 关于从savepoint启动作业报错 migration for MapState currently isn't supported.

成功了吗？ 我这边报的是另外一个错误， org.apache.flink.util.StateMigrationException: The new state serializer cannot be incompatible 使用的版本的是fink 1.9.0 具体操作是： trigger savepoint后从savepoint读取就是这个错误 使用的是MapState[String,Void] 在scala代码 ... 25 more Caused by: java.io.IOException: Failed to open user defined function at