Dead-Letter Topic Partition Selection
By default, records are published to the Dead-Letter topic using the same partition as the original record. This means the Dead-Letter topic must have at least as many partitions as the original record.
To change this behavior, add a DlqPartitionFunction implementation as a @Bean to the application context.
Only one such bean can be present.
The function is provided with the consumer group, the failed ConsumerRecord and the exception.
For example, if you always want to route to partition 0, you might use:
@Bean
public DlqPartitionFunction partitionFunction() {
return (group, record, ex) -> 0;
}
If you set a consumer binding’s dlqPartitions property to 1 (and the binder’s minPartitionCount is equal to 1), there is no need to supply a DlqPartitionFunction; the framework will always use partition 0.
If you set a consumer binding’s dlqPartitions property to a value greater than 1 (or the binder’s minPartitionCount is greater than 1), you must provide a DlqPartitionFunction bean, even if the partition count is the same as the original topic’s.
|
It is also possible to define a custom name for the DLQ topic.
In order to do so, create an implementation of DlqDestinationResolver as a @Bean to the application context.
When the binder detects such a bean, that takes precedence, otherwise it will use the dlqName property.
If neither of these are found, it will default to error.<destination>.<group>.
Here is an example of DlqDestinationResolver as a @Bean.
@Bean
public DlqDestinationResolver dlqDestinationResolver() {
return (rec, ex) -> {
if (rec.topic().equals("word1")) {
return "topic1-dlq";
}
else {
return "topic2-dlq";
}
};
}One important thing to keep in mind when providing an implementation for DlqDestinationResolver is that the provisioner in the binder will not auto create topics for the application.
This is because there is no way for the binder to infer the names of all the DLQ topics the implementation might send to.
Therefore, if you provide DLQ names using this strategy, it is the application’s responsibility to ensure that those topics are created beforehand.
