Confluent Cloud Cluster and Topic Configuration Settings¶

This topic describes the default Apache Kafka® cluster and topic configuration settings in Confluent Cloud as well as the topic settings that can be edited. For a complete description of all Kafka configurations, see Confluent Platform Configuration Reference.

When editing topic and cluster settings, remember the following:

You cannot edit cluster settings on Confluent Cloud on Basic or Standard clusters, but you can edit certain topic configurations after a topic has been created. For a list of editable topic settings, see Custom topic settings for all cluster types.
You can change some configuration settings on Dedicated clusters using the Kafka CLI. See Custom topic and cluster settings for Dedicated clusters.
You cannot access internal Kafka topics, and therefore they cannot be edited. For example, the internal topic __consumer_offsets is not accessible. Also, topics that are not accessible do not count toward partition limits or partition billing charges. Topics created by managed Connectors and ksqlDB are accessible.

Custom topic settings for all cluster types¶

The following table lists default parameter values for custom topics. The table also includes minimum and maximum values where they are relevant, as well as whether the parameters are editable.

Important

The following limitations apply to changing parameter values after a topic has been created:

You cannot change the cleanup.policy from delete to compact after a topic has been created.
The num.partitions value can only be increased and not decreased after a topic is created.
All other editable settings can be changed after topic creation, but the limits that applied at topic creation still apply.

Parameter Name	Default	Min/Max	Editable
cleanup.policy	Delete		No
compression.type	producer		No
default.replication.factor	3		No
delete.retention.ms	86400000	Max: 63113904000	Yes
file.delete.delay.ms	60000		No
flush.messages	9223372036854775807		No
flush.ms	9223372036854775807		No
index.interval.bytes	4096		No
max.message.bytes (Dedicated)	2097164	Max : 20971520	Yes
max.message.bytes (Standard, Basic)	2097164	Max : 8388608	Yes
max.compaction.lag.ms	9223372036854775807	Min: 604800000	Yes
message.downconversion.enable	true		No
message.format.version	2.3-IV1		No
message.timestamp.difference.max.ms	9223372036854775807		Yes
message.timestamp.type	CreateTime		Yes
min.cleanable.dirty.ratio	0.5		No
min.compaction.lag.ms	0		Yes
min.insync.replicas	2		Yes
num.partitions	6		Yes, can be increased via API.
offsets.retention.minutes	10080		No
preallocate	false		No
retention.bytes	-1		Yes
retention.ms	604800000		Yes
segment.bytes	104857600	Min: 52428800 Max: 1073741824	Yes
segment.index.bytes	10485760		No
segment.jitter.ms	0		No
segment.ms	604800000	Min: 600000	Yes
unclean.leader.election.enable	false		No

Custom topic and cluster settings for Dedicated clusters¶

Some settings for Dedicated clusters can be modified using the Kafka CLI.

Changes to the the settings that follow are dynamically applied to your Confluent Cloud cluster.

Important

These settings apply only to Dedicated clusters and cannot be modified on Basic or Standard clusters.

Enable automatic topic creation (auto.create.topics.enable)

kafka-configs --bootstrap-server <bootstrap> --command-config config.properties --entity-type brokers --entity-default --alter --add-config auto.create.topics.enable=true

Restrict allowed SSL cipher suites (ssl.cipher.suites)

kafka-configs --bootstrap-server <bootstrap> --command-config config.properties --entity-type brokers --entity-default --alter --add-config ssl.cipher.suites=<list>

The valid list of ciphers includes:

TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256

Set the default number of partitions for new topics (num.partitions)

kafka-configs --bootstrap-server <bootstrap> --command-config <auth-configs> --entity-type brokers --entity-default --alter --add-config num.partitions=<int>

Set the default maximum log compaction time for new topics (log.cleaner.max.compaction.lag.ms)

kafka-configs --bootstrap-server <bootstrap> --command-config <auth-configs> --entity-type brokers --entity-default --alter --add-config log.cleaner.max.compaction.lag.ms=<int>

Set the default log retention time for new topics (log.retention.ms)

kafka-configs --bootstrap-server <bootstrap> --command-config <auth-configs> --entity-type brokers --entity-default --alter --add-config log.retention.ms=<int>