Github user aljoscha commented on a diff in the pull request:
https://github.com/apache/flink/pull/4357#discussion_r128754182
--- Diff:
flink-connectors/flink-connector-kafka-base/src/main/java/org/apache/flink/streaming/connectors/kafka/FlinkKafkaConsumerBase.java
---
@@ -517,16 +519,13 @@ public void
initializeState(FunctionInitializationContext context) throws Except
LOG.debug("Using the following offsets:
{}", restoredState);
}
}
- if (restoredState != null && restoredState.isEmpty()) {
- restoredState = null;
- }
} else {
LOG.info("No restore state for FlinkKafkaConsumer.");
}
}
@Override
- public void snapshotState(FunctionSnapshotContext context) throws
Exception {
+ public final void snapshotState(FunctionSnapshotContext context) throws
Exception {
--- End diff --
The concern here is that not making the methods final makes it easy for
contributors to accidentally override them. We don't have specific unit tests
for the 0.9 `FlinkKafkaConsumer` or the 0.10 `FlinkKafkaConsumer` and only test
the base `FlinkKafkaConsumerBase`. This is OK, as long as specific
implementations don't override important methods. If the
`FlinkKafkaConsumer090` did override the `snapshot()`/`restore()` methods, for
example, no tests would catch this.
@tzulitai I don't want to discuss here about these methods to much since we
want to get the fixes in for release 1.3.2. A way around the problem is to turn
the `FlinkKafkaConsumerBaseTest` into an abstract
`FlinkKafkaConsumerBaseTestBase` that has an abstract method
`createTestingConsumer(List<KafkaTopicPartition> mockFetchedPartitions)` that
creates a "dummy" consumer for a specific Kafka version. Then we would have
individual `FlinkKafkaConsumer09Test`, `FlinkKafkaConsumer010Test` and so on
that derive form the abstract test base and just implement the method for
creating the testing consumer.
What do you think?
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