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https://issues.apache.org/jira/browse/BAHIR-183?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16770130#comment-16770130
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Lukasz Antoniak commented on BAHIR-183:
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[~yanlin-Lynn], I am not sure whether offset management is implemented 
correctly here. We store lots of messages in one HDFS file and loose track of 
singe message offset. Did you try to implement `MqttClientPersistence` 
interface to store data in HDFS? The implementation would be a lot cleaner this 
way, as user would only choose between memory, local file, or HDFS storage.

> Using HDFS for saving message for mqtt source
> ---------------------------------------------
>
>                 Key: BAHIR-183
>                 URL: https://issues.apache.org/jira/browse/BAHIR-183
>             Project: Bahir
>          Issue Type: Improvement
>          Components: Spark Structured Streaming Connectors
>    Affects Versions: Spark-2.2.0
>            Reporter: Wang Yanlin
>            Assignee: Wang Yanlin
>            Priority: Major
>             Fix For: Spark-2.4.0
>
>
> Currently in spark-sql-streaming-mqtt, the received mqtt message is saved in 
> a local file by driver, this will have the risks of losing data for cluster 
> mode when application master failover occurs. So saving in-coming mqtt 
> messages using a director in checkpoint will solve this problem.



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