Details
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Type:
Bug
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Status: Resolved
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Priority:
Major
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Resolution: Fixed
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Affects Version/s: 2.17.1
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Fix Version/s: 2.18.0
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Component/s: camel-kafka
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Labels:None
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Environment:
Spring Boot 1.4.0.M3 with Tomcat
Java 8
Camel 2.17.1
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Estimated Complexity:Unknown
Description
After triggering CamelContext#close() method the execution will reach org.apache.camel.component.kafka.KafkaConsumer#doStop where the shutdown of the executor instance will be triggered and where in it's turn the interruption of the submitted to the executor threads should happen (by reaching the native implementation of Thread#interrupt())
According to https://docs.oracle.com/javase/8/docs/api/java/lang/Thread.html#interrupt-- interrupt method will only set a corresponding status to the thread, but will not terminate it.
Problem is in the line KafkaConsumer.java:108:
ConsumerRecords<Object, Object> records = consumer.poll(Long.MAX_VALUE);
In the Kafka implementation of the poll method this will lead to almost infinite while loop which is not checking the thread status and this loop will exit only in case of receiving a message from a broker. Only after exciting the loop the interrupted status of the thread will be discovered and the thread will be terminated.
This leads to a couple of problems:
1. The KafkaConsumers remain alive until receiving at least one more message from the broker.
2. As the CamelContext at this point of time is most likely already shut down, the received message is not going to be processed, but will be acknowledged to the broker. So effectively the message gets lost.
A potential fix would be to either make the poll timeout reasonably small or configurable.
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