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Re: Weird behaviour after change sources in a job.

Hi Juan,

I think this is somehow expected behaviour. Flink, in order to provide proper processing semantics keeps track of partitions offsets internally, and checkpoints those offsets. FlinkKafkaConsumer supports

also new partitions discovery. Having in mind both of those features, if you restart your job with savepoint/checkpoint but with changed topic, it will restore old partitions with offsets from checkpoint, and will discover partitions

from the new topic. This is why it consumes from both old and new topic. If you defined your source manually (you were not using Kafka010TableSource) what you can do is set new uid for the source and enable allowNonRestoredState. This way you will keep state for all other operators, but you will lose

information about offsets in Kafka.

I also cc @Gordon, who might want to add something to this.

On 12/09/18 18:03, Juan Gentile wrote:



We have found a weird issue while replacing the source in one of our Flink SQL Jobs.


We have a job which was reading from a Kafka topic (with externalize checkpoints) and we needed to change the topic while keeping the same logic for the job/SQL.

After we restarted the job, instead of consuming from the new Kafka topic, it consumed from both! Duplicating the input of our job.

We were able to reproduce the issue but we don’t understand if this is a bug or expected behavior and in this case we should have restarted from a clean state.

We are using Flink 1.4 at the moment and Kafka


Thank you,


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