Topic Configuration Properties

A topic-level property sets a Redpanda or Kafka configuration for a particular topic.

Many topic-level properties have corresponding cluster properties that set a default value for all topics of a cluster. To customize the value for a topic, you can set a topic-level property that overrides the value of the corresponding cluster property.

Topic property Corresponding cluster property

cleanup.policy

log_cleanup_policy

flush.bytes

raft_replica_max_pending_flush_bytes

flush.ms

raft_replica_max_flush_delay_ms

initial.retention.local.target.ms

initial_retention_local_target_ms_default

retention.bytes

retention_bytes

retention.ms

log_retention_ms

segment.ms

log_segment_ms

segment.bytes

log_segment_size

compression.type

log_compression_type

message.timestamp.type

log_message_timestamp_type

max.message.bytes

kafka_batch_max_bytes

replication.factor

default_topic_replication

write.caching

write_caching_default

The SOURCE output of the rpk topic describe <topic> command describes how the property is set for the topic:

  • DEFAULT_CONFIG is set by a Redpanda default.

  • DYNAMIC_TOPIC_CONFIG is set by the user specifically for the topic and overrides inherited default configurations, such as a default or a cluster-level property.

Although rpk topic describe doesn’t report replication.factor as a configuration, replication.factor can indeed be set by using the rpk topic alter-config command.

Examples

The following examples show how to configure topic-level properties. Set a topic-level property for a topic to override the value of corresponding cluster property.

Create topic with topic properties

To set topic properties when creating a topic, use the rpk topic create command with the -c option.

For example, to create a topic with the cleanup.policy property set to compact:

  • Local

  • Kubernetes

rpk topic create -c cleanup.policy=compact <topic-name>
kubectl exec <pod-name> -- rpk topic create -c cleanup.policy=compact<topic-name>

To configure multiple properties for a topic, use the -c option for each property.

For example, to create a topic with all necessary properties for Tiered Storage:

  • Local

  • Kubernetes

rpk topic create -c redpanda.remote.recovery=true -c redpanda.remote.write=true -c redpanda.remote.read=true <topic-name>
kubectl exec <pod-name> -- rpk topic create -c redpanda.remote.recovery=true -c redpanda.remote.write=true -c redpanda.remote.read=true <topic-name>

Modify topic properties

To modify topic properties of an existing topic, use the rpk topic alter-config command.

For example, to modify a topic’s retention.ms property:

  • Local

  • Kubernetes

rpk topic alter-config <topic-name> --set retention.ms=<retention-time>
kubectl exec <pod-name> -- rpk topic alter-config <topic-name> --set retention.ms=<retention-time>

Properties

This section describes all supported topic-level properties.

Disk space properties

Configure properties to manage the disk space used by a topic:

  • Clean up log segments by deletion and/or compaction (cleanup.policy).

  • Retain logs up to a maximum size per partition before cleanup (retention.bytes).

  • Retain logs for a maximum duration before cleanup (retention.ms).

  • Periodically close an active log segment (segment.ms).

  • Limit the maximum size of an active log segment (segment.bytes).

  • Cache batches until the segment appender chunk is full, instead of fsyncing for every acks=all write (write.caching). With write.caching enabled, fsyncs follow flush.ms and flush.bytes, whichever is reached first.


cleanup.policy

The cleanup policy to apply for log segments of a topic.

When cleanup.policy is set, it overrides the cluster property log_cleanup_policy for the topic.

Default: [delete]

Values:

  • [delete] - Deletes data according to size-based or time-based retention limits, or both.

  • [compact] - Deletes data according to a key-based retention policy, discarding all but the latest value for each key.

  • [compact,delete] - The latest values are kept for each key, while the remaining data is deleted according to retention limits.

Related topics:


flush.ms

The maximum delay (in ms) between two subsequent fsyncs. After this delay, the log is automatically fsynced.

Default: 100

Related topics:


flush.bytes

The maximum bytes not fsynced per partition. If this configured threshold is reached, the log is automatically fsynced, even though it wasn’t explicitly requested.

Default: 262144

Related topics:


retention.bytes

A size-based retention limit that configures the maximum size that a topic partition can grow before becoming eligible for cleanup.

If retention.bytes is set to a positive value, it overrides the cluster property retention_bytes for the topic, and the total retained size for the topic is retention.bytes multiplied by the number of partitions for the topic.

When both size-based (retention.bytes) and time-based (retention.ms) retention limits are set, cleanup occurs when either limit is reached.

Default: null

Related topics:


retention.ms

A time-based retention limit that configures the maximum duration that a log’s segment file for a topic is retained before it becomes eligible to be cleaned up. To consume all data, a consumer of the topic must read from a segment before its retention.ms elapses, otherwise the segment may be compacted and/or deleted. If a non-positive value, no per-topic limit is applied.

If retention.ms is set to a positive value, it overrides the cluster property log_retention_ms for the topic.

When both size-based (retention.bytes) and time-based (retention.ms) retention limits are set, the earliest occurring limit applies.

Default: null

Related topics:


segment.ms

The maximum duration that a log segment of a topic is active (open for writes and not deletable). A periodic event, with segment.ms as its period, forcibly closes the active segment and transitions, or rolls, to a new active segment. The closed (inactive) segment is then eligible to be cleaned up according to cleanup and retention properties.

If set to a positive duration, segment.ms overrides the cluster property log_segment_ms and its lower and upper bounds set by log_segment_ms_min and log_segment_ms_max, respectively.

Default: null

Related topics:


segment.bytes

The maximum size of an active log segment for a topic. When the size of an active segment exceeds segment.bytes, the segment is closed and a new active segment is created. The closed, inactive segment is then eligible to be cleaned up according to retention properties.

When segment.bytes is set to a positive value, it overrides the cluster property log_segment_size for the topic.

Default: null

Related topics:


write.caching

The write caching mode to apply to a topic.

When write.caching is set, it overrides the cluster property write_caching_default. Write caching acknowledges a message as soon as it is received and acknowledged on a majority of brokers, without waiting for it to be written to disk. With acks=all, this provides lower latency while still ensuring that a majority of brokers acknowledge the write. Fsyncs follow flush.ms and flush.bytes, whichever is reached first.

Default: false

Values:

Related topics:


Message properties

Configure properties for the messages of a topic:

compression.type

The type of compression algorithm to apply for all messages of a topic. When a compression type is set for a topic, producers compress and send messages, nodes (brokers) store and send compressed messages, and consumers receive and uncompress messages.

Enabling compression reduces message size, which improves throughput and decreases storage for messages with repetitive values and data structures. The trade-off is increased CPU utilization and network latency to perform the compression. You can also enable producer batching to increase compression efficiency, since the messages in a batch likely have repeated data that can be compressed.

When compression.type is set, it overrides the cluster property log_compression_type for the topic.

The valid values of compression.type are taken from log_compression_type and differ from Kafka’s compression types.

Default: none

Values:

  • none

  • gzip

  • lz4

  • snappy

  • zstd

  • producer

Related topics:


message.timestamp.type

The source of a message’s timestamp: either the message’s creation time or its log append time.

When message.timestamp.type is set, it overrides the cluster property log_message_timestamp_type for the topic.

Default: CreateTime

Values:

  • CreateTime

  • LogAppendTime


max.message.bytes

The maximum size of a message or batch of a topic. If a compression type is enabled, max.message.bytes sets the maximum size of the compressed message or batch.

If max.message.bytes is set to a positive value, it overrides the cluster property kafka_batch_max_bytes for the topic.

Default: null

Related topics:


Tiered Storage properties

Configure properties to manage topics for Tiered Storage:

redpanda.remote.write

A flag for enabling Redpanda to upload data for a topic from local storage to object storage. When set to true together with redpanda.remote.read, it enables the Tiered Storage feature.

Default: false

Related topics:


redpanda.remote.read

A flag for enabling Redpanda to fetch data for a topic from object storage to local storage. When set to true together with redpanda.remote.write, it enables the Tiered Storage feature.

Default: false

Related topics:


initial.retention.local.target.bytes

A size-based initial retention limit for Tiered Storage that determines how much data in local storage is transferred to a partition replica when a cluster is resized. If null (default), all locally retained data is transferred.

Default: null

Related topics:


initial.retention.local.target.ms

A time-based initial retention limit for Tiered Storage that determines how much data in local storage is transferred to a partition replica when a cluster is resized. If null (default), all locally retained data is transferred.

Default: null

Related topics:


retention.local.target.bytes

A size-based retention limit for Tiered Storage that configures the maximum size that a topic partition in local storage can grow before becoming eligible for cleanup. It applies per partition and is equivalent to retention.bytes without Tiered Storage.

Default: null

Related topics:


retention.local.target.ms

A time-based retention limit for Tiered Storage that sets the maximum duration that a log’s segment file for a topic is retained in local storage before it’s eligible for cleanup. This property is equivalent to retention.ms without Tiered Storage.

Default: 86400000

Related topics:


redpanda.remote.recovery

A flag that enables the recovery or reproduction of a topic from object storage for Tiered Storage. The recovered data is saved in local storage, and the maximum amount of recovered data is determined by the local storage retention limits of the topic.

You can only configure redpanda.remote.recovery when you create a topic. You cannot apply this setting to existing topics.

Default: false

Related topics:


redpanda.remote.delete

A flag that enables deletion of data from object storage for Tiered Storage when it’s deleted from local storage for a topic.

redpanda.remote.delete doesn’t apply to Remote Read Replica topics: a Remote Read Replica topic isn’t deleted from object storage when this flag is true.

Default:

  • false for topics created using Redpanda 22.2 or earlier.

  • true for topics created in Redpanda 22.3 and later, including new topics on upgraded clusters.

Related topics:


Remote Read Replica properties

Configure properties to manage topics for Remote Read Replicas.

redpanda.remote.readreplica

The name of the object storage bucket for a Remote Read Replica topic.

Setting redpanda.remote.readreplica together with either redpanda.remote.read or redpanda.remote.write results in an error.

Default: null

Related topics:


Redpanda topic properties

Configure Redpanda-specific topic properties.

replication.factor

The number of replicas of a topic to save in different nodes (brokers) of a cluster.

If replication.factor is set to a positive value, it overrides the cluster property default_topic_replication for the topic.

Although replication.factor isn’t returned or displayed by rpk topic describe as a valid Kafka property, you can set it using rpk topic alter-config. When the replication.factor of a topic is altered, it isn’t simply a property value that’s updated, but rather the actual replica sets of topic partitions that are changed.

Default: null

Related topics: