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https://issues.apache.org/jira/browse/KAFKA-18543?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ming-Yen Chung resolved KAFKA-18543.
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Reviewer: Chia-Ping Tsai
Assignee: Ming-Yen Chung
Resolution: Resolved
> Strict validation of bootstrap.servers in Kafka Clients 3.8.x causing issues
> with multiline configurations
> ----------------------------------------------------------------------------------------------------------
>
> Key: KAFKA-18543
> URL: https://issues.apache.org/jira/browse/KAFKA-18543
> Project: Kafka
> Issue Type: Bug
> Components: clients
> Affects Versions: 3.8.1
> Reporter: Nadina Florea
> Assignee: Ming-Yen Chung
> Priority: Major
>
> Hello,
> We encountered an issue when upgrading to *Kafka Clients 3.8.x* (from 3.7.2).
> The problem occurs when the bootstrap.servers configuration is defined in
> YAML files using multiline syntax (e.g., using >, or as a list of brokers).
> Previously, with Kafka Clients 3.7.x, this configuration worked fine even
> with newlines in the brokers’ addresses, but in Kafka Clients 3.8.x, the
> validation was made stricter, resulting in the following error:
> {code:java}
> org.apache.kafka.common.config.ConfigException: Invalid url in
> bootstrap.servers
> {code}
> Environment:
> • Kafka Clients Version: 3.8.1
> • Apache Camel Version: 4.9.0
> • Spring Boot Version: 3.4.1
> • Java Version: 17
> We are using Apache Camel to connect to Kafka, and Camel simply passes the
> Spring Boot auto-configured values (including bootstrap.servers) to Kafka.
> Camel doesn’t modify the configuration itself.
> Steps to Reproduce:
> 1. Define bootstrap.servers in application.yaml using multiline syntax:
> {code:java}
> camel:
> component:
> kafka:
> brokers: >-
> broker1:9092,
> broker2:9092{code}
> 2. Use the following setup in logback-spring.xml to configure Kafka Appender:
> {code:java}
> <springProperty name="brokers" source="camel.component.kafka.brokers" />
> <appender name="KAFKA" class="ch.qos.logback.classic.net.KafkaAppender">
> <kafkaProp>
> bootstrap.servers=${brokers}
> </kafkaProp>
> </appender>{code}
> 3. Run the application.
> The application fails to start with the following error:
> _*org.apache.camel.RuntimeCamelException:
> org.apache.kafka.common.config.ConfigException: Invalid url in
> bootstrap.servers: broker2:9092*_
>
> • The error occurs due to the stricter validation introduced in
> KAFKA-17584., which does not allow newline characters or improperly formatted
> values for bootstrap.servers.
> • Previously, Kafka Clients 3.7.x seemed to accept multiline configurations
> more leniently.
> *Is this stricter validation behavior intentional in Kafka Clients 3.8.x, and
> is it a permanent change?*
> We would like to understand whether this behavior is expected or if it could
> be reconsidered in future Kafka versions to support multiline configurations,
> as this change has introduced compatibility issues with Camel applications.
> For users using Camel with Spring Boot, this issue is particularly
> problematic since the brokers’ list often appears on multiple lines in YAML
> files for better readability. This could make configuration difficult to
> manage if forced onto a single line.
> It would be helpful if Kafka allowed multiline configuration for
> bootstrap.servers to avoid forcing users to put all brokers on a single line.
>
> • Similar issue already reported: KAFKA-18171
> • When I updated my YAML configuration to write *bootstrap.servers on a
> single line* (e.g., broker1:9092,broker2:9092), the issue was resolved.
> • _Applications that use Spring Kafka directly without Camel are not affected
> by this issue._
> Thank you!
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