Github user JPercivall commented on a diff in the pull request:
https://github.com/apache/nifi/pull/563#discussion_r72330212
--- Diff:
nifi-nar-bundles/nifi-kafka-bundle/nifi-kafka-pubsub-processors/src/main/java/org/apache/nifi/processors/kafka/pubsub/ConsumeKafka.java
---
@@ -54,7 +72,12 @@
@InputRequirement(Requirement.INPUT_FORBIDDEN)
@CapabilityDescription("Consumes messages from Apache Kafka")
@Tags({ "Kafka", "Get", "Ingest", "Ingress", "Topic", "PubSub", "Consume"
})
-public class ConsumeKafka extends AbstractKafkaProcessor<Consumer<byte[],
byte[]>> {
+@Stateful(scopes = {Scope.EXTERNAL}, description = "After consuming
messages, ConsumeKafka commits its offset information to Kafka" +
+ " so that the state of a consumer group can be retained across
events such as consumer reconnect." +
+ " Offsets can be cleared when there is no consumer subscribing
with the same consumer group id." +
+ " It may take more than 30 seconds for a consumer group to become
able to be cleared after it is stopped from NiFi." +
+ " Once offsets are cleared, ConsumeKafka will resume consuming
messages based on Offset Reset configuration.")
+public class ConsumeKafka extends AbstractKafkaProcessor<Consumer<byte[],
byte[]>> implements ExternalStateManager {
--- End diff --
Since "ExternalStateManager" is something that the developer will need to
implement if they will use it, this should be documented in the Developer guide
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