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The following commit(s) were added to refs/heads/4.0 by this push:
new e8cc75b8ced KIP-966 part 1 release doc (#18898)
e8cc75b8ced is described below
commit e8cc75b8cede82e8106687ea8801dca160fbfd83
Author: Calvin Liu <[email protected]>
AuthorDate: Mon Feb 24 15:19:18 2025 -0800
KIP-966 part 1 release doc (#18898)
Add notes to explain how ELR and how to manage ELR.
Reviewers: Colin P. McCabe <[email protected]>
---
docs/ops.html | 26 ++++++++++++++++++++++++++
docs/upgrade.html | 7 +++++++
2 files changed, 33 insertions(+)
diff --git a/docs/ops.html b/docs/ops.html
index 9c85704c4f2..48b4124374c 100644
--- a/docs/ops.html
+++ b/docs/ops.html
@@ -4279,6 +4279,32 @@ $ bin/kafka-topics.sh --create --topic tieredTopic
--bootstrap-server localhost:
<li><code>add.partitions.to.txn.retry.backoff.max.ms</code></li>
</ul>
+ <h3 class="anchor-heading"><a id="eligible_leader_replicas"
class="anchor-link"></a><a href="#eligible_leader_replicas">6.12 Eligible
Leader Replicas</a></h3>
+
+ <h4 class="anchor-heading"><a id="eligible_leader_replicas_overview"
class="anchor-link"></a><a
href="#eligible_leader_replicas_overview">Overview</a></h4>
+
+ <p>Starting from Apache Kafka 4.0, Eligible Leader Replicas (<a
href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-966%3A+Eligible+Leader+Replicas";>KIP-966
Part 1</a>)
+ is available for the users to an improvement to Kafka replication. As the
"strict min ISR" rule has been generally applied, which means the high
watermark for the data partition can't advance
+ if the size of the ISR is smaller than the min
ISR(<code>min.insync.replicas</code>), it makes some replicas that are not in
the ISR safe to become the leader. The KRaft controller
+ stores such replicas in the PartitionRecord field called <code>Eligible
Leader Replicas</code>. During the leader election, the controller will select
the leaders
+ with the following order:</p>
+ <ul>
+ <li>If ISR is not empty, select one of them.</li>
+ <li>If ELR is not empty, select one that is not fenced.</li>
+ <li>Select the last known leader if it is unfenced. This is a similar
behavior prior to the 4.0 when all the replicas are offline.</li>
+ </ul>
+
+ <h4 class="anchor-heading"><a id="eligible_leader_replicas_upgrade"
class="anchor-link"></a><a href="#eligible_leader_replicas_upgrade">Upgrade &
Downgrade</a></h4>
+
+ <p>The ELR is not enabled by default for 4.0. To enable the new protocol on
the server, set <code>eligible.leader.replicas.version=1</code>. After that the
upgrade, the KRaft
+ controller will start tracking the ELR. </p>
+ <p>Downgrades are safe to perform by setting
<code>eligible.leader.replicas.version=0</code>.</p>
+
+ <h4 class="anchor-heading"><a id="eligible_leader_replicas_tool"
class="anchor-link"></a><a href="#eligible_leader_replicas_tool">Tool</a></h4>
+ <p>The ELR fields can be checked through the API DescribeTopicPartitions.
The admin client can fetch the ELR info by describing the topics.
+ Also note that, if <code>min.insync.replicas</code> is updated for a
topic, the ELR field will be cleaned. If cluster default min ISR is updated,
+ all the ELR fields will be cleaned.</p>
+
</script>
<div class="p-ops"></div>
diff --git a/docs/upgrade.html b/docs/upgrade.html
index 2366818c55f..26b639bf66f 100644
--- a/docs/upgrade.html
+++ b/docs/upgrade.html
@@ -71,6 +71,13 @@
When using 4.0 producer clients, the producer epoch is bumped on
every transaction to ensure every transaction includes the intended messages
and duplicates are not
written as part of the next transaction. Downgrading the protocol
is safe. For more information check <a
href="/{{version}}/documentation.html#transaction_protocol">here</a>
</li>
+ <li>
+ Eligible Leader Replicas (<a
href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-966%3A+Eligible+Leader+Replicas";>KIP-966
Part 1</a>)
+ enhances the replication protocol for the Apache Kafka 4.0. Now
the KRaft controller keeps track of the data partition replicas that are
+ not included in ISR but are safe to be elected as leader without
data loss. Such replicas are stored in the partition metadata as
+ the <code>Eligible Leader Replicas</code>(ELR).
+ For more information check <a
href="/{{version}}/documentation.html#eligible_leader_replicas">here</a>
+ </li>
<li>
Since Apache Kafka 4.0.0, we have added a system property
("org.apache.kafka.sasl.oauthbearer.allowed.urls") to
set the allowed URLs as SASL OAUTHBEARER token or jwks endpoints.
By default, the value is an empty list.
