ludun624 edited a comment on issue #11733:
URL: https://github.com/apache/druid/issues/11733#issuecomment-944880185


   I can reproduce this issue in 0.23.0, 0.20.2 
   It seems the cause of this issue is from 
`druid.extensions.loadList=["postgres-metadata-storage","mysql-metadata-storage"]`
 , for obvious reasons Druid never expect user to use 2 type of 
metadata-storage, and when you try to do that, it causes conflict in binding 
phase because we are binding the shared classes(such as AuditManager.class and 
AuditManagerProvider.class) twice.
   By looking at document 
[here](https://druid.apache.org/docs/latest/ingestion/native-batch.html#sql-input-source)
 , sql ingestion ties metadata-storage extension for same type of RDBMS, which 
imply an assumption that when users want to ingest from one RDBMS(for 
example,MySQL), user would reuse same type of RDBMS for metadata-storage, this 
poor assumption never considered the case when people use Druid to ingest from 
more than 1 type of RDBMS.
   
   @a2l007 correct me if I`m wrong please, from my understanding using sql 
ingest to ingest data from more than 1 type of RDBMS is likely unsupported and 
unintended in Druid right now.
   
   A workaround for this issue can be :
   1. If it`s a one time operation, we can dump the table from mysql and/or 
postgres into CSV file, then import to druid from CSV
   2. Or if it`s a periodically operation, stream the content to message queues 
like Kafka or Kinesis, then use Kafka/Kinesis indexer


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