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https://issues.apache.org/jira/browse/BAHIR-183?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16870492#comment-16870492
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Wang Yanlin commented on BAHIR-183:
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hi, [~lukasz.antoniak], for your concern of lost message, I have checked the
method *messageArrived* in interface
*org.eclipse.paho.client.mqttv3.MqttCallback*. The message any QoS 1 or 2
message will be redelivered by the server if we throw exception before return.
I save message data in hdfs back-end in *messageArrived* implementation, so I
think we will not lost any message in this situtation.
> 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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