Demogorgon314 commented on code in PR #21246:
URL: https://github.com/apache/pulsar/pull/21246#discussion_r1374325957
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pulsar-client-api/src/main/java/org/apache/pulsar/client/api/ConsumerBuilder.java:
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@@ -831,6 +831,16 @@ public interface ConsumerBuilder<T> extends Cloneable {
*/
ConsumerBuilder<T> autoScaledReceiverQueueSizeEnabled(boolean enabled);
+ /**
+ * Sets the {@link SubscriptionIsolationLevel} for the consumer.
+ *
+ * @param subscriptionIsolationLevel If READ_COMMITTED is selected, the
Consumer can only consume all transactional messages which have been committed,
+ * else if READ_UNCOMMITTED is selected,
the Consumer can consume all messages, even transactional messages which have
been aborted.
+ * Note that this is a subscription
dimension configuration, and all consumers under the same subscription need to
be configured with the same IsolationLevel.
Review Comment:
There are differences between Kafka and Pulsar in filtering the aborted
message.
Kafka filters the aborted message on the client side, so if the client uses
`READ_UNCOMMITED`, the client can't feel the ongoing transaction, the client is
only able to filter the markers. If we need to filter the abort message on the
kafka client, it requires to response of the `abortedTransactions` data each
fetch, which will reduce the consumption performance.
Pulsar has different implements for filter parts, the filter logic is on the
Broker side. If it is to reduce read and write latency, it is okay.
But I think reading all messages just like Kafka is beneficial in the
following cases:
In the event of issues or during development and testing phases, having
access to all messages, including uncommitted ones, can be valuable for
debugging and troubleshooting.
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