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https://issues.apache.org/jira/browse/FLINK-24851?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17443941#comment-17443941
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Arseniy Tashoyan commented on FLINK-24851:
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I mean the situation, when we specify all Kafka consumer settings via
*builder.setProperties()*. In this case, there is no conflict with the
builder-expressed logic.
Why it is important? We have a config file (for example, Typesafe Config). All
Kafka-consumer settings are listed in the config file like this:
{code:yaml}
kafka-consumer {
"bootstrap.servers" = "localhost:9092"
"group.id" = "group1"
"auto.offset.reset" = "latest"
}
{code}
When reading this config file, we get a Map:
{code:scala}
val settings: Map[String, String] = ConfigLoader.load(...)
{code}
These settings are exactly as documented by Kafka. We can push them directly to
Kafka Client API, without interpreting in the Flink-level or application-level
code:
{code:scala}
val kafkaSource = KafkaSource.builder()
.setProperties(settings)
.build()
{code}
This is convenient. We don't have to interpret Kafka settings - we let Kafka
Client API interpret Kafka settings.
Bonus: no need to construct java.util.Properties - accept plain Java
Map<String, String>.
> KafkaSourceBuilder: auto.offset.reset is ignored
> ------------------------------------------------
>
> Key: FLINK-24851
> URL: https://issues.apache.org/jira/browse/FLINK-24851
> Project: Flink
> Issue Type: Bug
> Components: Connectors / Kafka
> Affects Versions: 1.14.0
> Reporter: Arseniy Tashoyan
> Assignee: liwei li
> Priority: Major
> Labels: pull-request-available
>
> Creating KafkaSource like this:
> {code:scala}
> val props = new Properties()
> props.put("bootstrap.servers", "localhost:9092")
> props.put("group.id", "group1")
> props.put("auto.offset.reset", "latest")
> val kafkaSource = KafkaSource.builder[String]()
> .setProperties(props)
> .build()
> {code}
> The actually used value for _"auto.offset.reset"_ is *"earliest"* instead of
> configured *"latest"*.
> This occurs because _"auto.offset.reset"_ gets overridden by
> _startingOffsetsInitializer.getAutoOffsetResetStrategy().name().toLowerCase()_.
> The default value for _startingOffsetsInitializer_ is _"earliest"_.
> This behavior is misleading.
> This behavior imposes an inconvenience on configuring the Kafka connector. We
> cannot use the Kafka setting _"auto.offset.reset"_ as-is. Instead we must
> extract this particular setting from other settings and propagate to
> _KafkaSourceBuilder.setStartingOffsets()_:
> {code:scala}
> val kafkaSource = KafkaSource.builder[String]()
> .setProperties(props)
> .setStartingOffsets(
> OffsetsInitializer.committedOffsets(
> OffsetResetStrategy.valueOf(
> props.get(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG)
> .asInstanceOf[String]
> .toUpperCase(Locale.ROOT)
> )
> )
> )
> .build()
> {code}
> The expected behavior is to use the value of _"auto.offset.reset"_ provided
> by _KafkaSourceBuilder.setProperties()_ - unless overridden via
> _KafkaSourceBuilder. setStartingOffsets()_.
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