FlinkCDC问题集锦

1.  MySQL的账号权限问题

Caused by: java.sql.SQLSyntaxErrorException: Access denied; you need (at least one of) the RELOAD privilege(s) for this operation

问题原因：由于flinkcdc使用该账号在读取binlog文件的同时，会加锁对应的库表，读完以后，会释放锁。所以需要相关的操作权限。

这里锁表操作会影响到正常的在线业务的。

flink-connector-mysql-cdc 其实存在两个不同的版本，一个是ververica在维护的，一个是alibaba在维护的。
其中ververica维护的在2.0.2以上版本中就已经不存在全局锁表这种情况了。
目前已经测试成功，参考连接

2. 指定StartupOptions.latest() 会出现检查点保存空指针异常问题

这个场景是从MySQL到Kafka，设置了ck，MySQL的读取设置的是 StartupOptions.latest()

报错异常如下：

Caused by: org.apache.flink.runtime.checkpoint.CheckpointException: Could not complete snapshot 4 for operator Source: Custom Source (1/1)#3. Failure reason: Checkpoint was declined.
    at org.apache.flink.streaming.api.operators.StreamOperatorStateHandler.snapshotState(StreamOperatorStateHandler.java:241)
    at org.apache.flink.streaming.api.operators.StreamOperatorStateHandler.snapshotState(StreamOperatorStateHandler.java:162)
    at org.apache.flink.streaming.api.operators.AbstractStreamOperator.snapshotState(AbstractStreamOperator.java:371)
    at org.apache.flink.streaming.runtime.tasks.SubtaskCheckpointCoordinatorImpl.checkpointStreamOperator(SubtaskCheckpointCoordinatorImpl.java:697)
    at org.apache.flink.streaming.runtime.tasks.SubtaskCheckpointCoordinatorImpl.buildOperatorSnapshotFutures(SubtaskCheckpointCoordinatorImpl.java:618)
    at org.apache.flink.streaming.runtime.tasks.SubtaskCheckpointCoordinatorImpl.takeSnapshotSync(SubtaskCheckpointCoordinatorImpl.java:583)
    at org.apache.flink.streaming.runtime.tasks.SubtaskCheckpointCoordinatorImpl.checkpointState(SubtaskCheckpointCoordinatorImpl.java:309)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.lambda$performCheckpoint$9(StreamTask.java:1013)
    at org.apache.flink.streaming.runtime.tasks.StreamTaskActionExecutor$SynchronizedStreamTaskActionExecutor.runThrowing(StreamTaskActionExecutor.java:93)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.performCheckpoint(StreamTask.java:997)
    at org.apache.flink.streaming.runtime.tasks.StreamTask.triggerCheckpointAsyncInMailbox(StreamTask.java:921)
    ... 10 more
Caused by: java.lang.NullPointerException
    at com.alibaba.ververica.cdc.debezium.DebeziumSourceFunction.snapshotOffsetState(DebeziumSourceFunction.java:262)
    at com.alibaba.ververica.cdc.debezium.DebeziumSourceFunction.snapshotState(DebeziumSourceFunction.java:240)
    at org.apache.flink.streaming.util.functions.StreamingFunctionUtils.trySnapshotFunctionState(StreamingFunctionUtils.java:118)
    at org.apache.flink.streaming.util.functions.StreamingFunctionUtils.snapshotFunctionState(StreamingFunctionUtils.java:99)
    at org.apache.flink.streaming.api.operators.AbstractUdfStreamOperator.snapshotState(AbstractUdfStreamOperator.java:89)
    at org.apache.flink.streaming.api.operators.StreamOperatorStateHandler.snapshotState(StreamOperatorStateHandler.java:205)
    ... 20 more

按道理说，从最新的记录开始，如果没有最新的，那么应该是等待状态的，所以这里不知道为啥会报异常。

把 StartupOptions.latest() 改为StartupOptions.earliest() 就正常了。

这个报错信息是在使用alibaba的依赖包的情况下出现了，目前已经使用上面1中的方案解决了，具体参考连接