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MINOR: Tweak default group coordinator config & upgrade notes (#18948) 

This patch changes the default value of `group.coordinator.threads` to `4` and sets it priority to `HIGH`. This change makes it consistent with how we handle `num.network.threads` and `num.io.threads`. The patch also tweaks the upgrade notes.

Reviewers: Ismael Juma <ismael@juma.me.uk>
This commit is contained in:
David Jacot 2025-02-18 20:05:52 +01:00 committed by GitHub
parent 929a90da50
commit d847d5c464
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2 changed files with 5 additions and 9 deletions
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10
docs/upgrade.html
View File

@ -52,17 +52,13 @@
</li>
<li>
Apache Kafka 4.0 ships with a brand-new group coordinator implementation (See <a href="https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=217387038#KIP848:TheNextGenerationoftheConsumerRebalanceProtocol-GroupCoordinator">here</a>.
Functionally speaking, it implements all the same APIs. However, the group coordinator runs in its own dedicated threads.
The number of threads can be defined with the <code>group.coordinator.threads</code> configuration. It defaults to 1 and
must certainly be adjusted for production deployments.
Functionally speaking, it implements all the same APIs. There are reasonable defaults, but the behavior of the new
group coordinator can be tuned by setting the configurations with prefix <code>group.coordinator</code>.
</li>
<li>
The Next Generation of the Consumer Rebalance Protocol (<a href="https://cwiki.apache.org/confluence/display/KAFKA/KIP-848%3A+The+Next+Generation+of+the+Consumer+Rebalance+Protocol">KIP-848</a>)
is now Generally Available (GA) in Apache Kafka 4.0. The protocol is automatically enabled on the server when the upgrade to 4.0 is finalized.
Note that once the new protocol is used by consumer groups, care must be taken to downgrade to a previous version. Downgrading
to version 3.4.1 or above is safe. Downgrading to an earlier version requires to ensure that all the records in the
<code>__consumer_offsets</code> are removed because those versions cannot handle them. This can be achieved by deleting all the
consumer groups using the new protocol, disabling the new protocol and letting compaction remove the tombstones.
Note that once the new protocol is used by consumer groups, the cluster can only downgrade to version 3.4.1 or newer.
Check <a href="/{{version}}/documentation.html#consumer_rebalance_protocol">here</a> for details.
</li>
<li>

4
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/GroupCoordinatorConfig.java
View File

@ -92,7 +92,7 @@ public class GroupCoordinatorConfig {
public static final String GROUP_COORDINATOR_NUM_THREADS_CONFIG = "group.coordinator.threads";
public static final String GROUP_COORDINATOR_NUM_THREADS_DOC = "The number of threads used by the group coordinator.";
public static final int GROUP_COORDINATOR_NUM_THREADS_DEFAULT = 1;
public static final int GROUP_COORDINATOR_NUM_THREADS_DEFAULT = 4;
/** Consumer group configs */
public static final String CONSUMER_GROUP_SESSION_TIMEOUT_MS_CONFIG = "group.consumer.session.timeout.ms";
@ -229,7 +229,7 @@ public class GroupCoordinatorConfig {
public static final ConfigDef NEW_GROUP_CONFIG_DEF = new ConfigDef()
.define(GROUP_COORDINATOR_REBALANCE_PROTOCOLS_CONFIG, LIST, GROUP_COORDINATOR_REBALANCE_PROTOCOLS_DEFAULT,
ConfigDef.ValidList.in(Group.GroupType.documentValidValues()), MEDIUM, GROUP_COORDINATOR_REBALANCE_PROTOCOLS_DOC)
.define(GROUP_COORDINATOR_NUM_THREADS_CONFIG, INT, GROUP_COORDINATOR_NUM_THREADS_DEFAULT, atLeast(1), MEDIUM, GROUP_COORDINATOR_NUM_THREADS_DOC)
.define(GROUP_COORDINATOR_NUM_THREADS_CONFIG, INT, GROUP_COORDINATOR_NUM_THREADS_DEFAULT, atLeast(1), HIGH, GROUP_COORDINATOR_NUM_THREADS_DOC)
.define(GROUP_COORDINATOR_APPEND_LINGER_MS_CONFIG, INT, GROUP_COORDINATOR_APPEND_LINGER_MS_DEFAULT, atLeast(0), MEDIUM, GROUP_COORDINATOR_APPEND_LINGER_MS_DOC)
// Internal configuration used by integration and system tests.
.defineInternal(NEW_GROUP_COORDINATOR_ENABLE_CONFIG, BOOLEAN, NEW_GROUP_COORDINATOR_ENABLE_DEFAULT, null, MEDIUM, NEW_GROUP_COORDINATOR_ENABLE_DOC);