changing kafka retention period during runtime

With Kafka 0.8.1.1, how do I change the log retention time while it's running? The documentation says the property is log.retention.hours, but trying to change it using kafka-topics.sh returns this error

$ bin/kafka-topics.sh --zookeeper zk.yoursite.com --alter --topic as-access --config topic.log.retention.hours=24
Error while executing topic command requirement failed: Unknown configuration "topic.log.retention.hours".
java.lang.IllegalArgumentException: requirement failed: Unknown configuration "topic.log.retention.hours".
    at scala.Predef$.require(Predef.scala:145)
    at kafka.log.LogConfig$$anonfun$validateNames$1.apply(LogConfig.scala:138)
    at kafka.log.LogConfig$$anonfun$validateNames$1.apply(LogConfig.scala:137)
    at scala.collection.Iterator$class.foreach(Iterator.scala:631)
    at scala.collection.JavaConversions$JEnumerationWrapper.foreach(JavaConversions.scala:479)
    at kafka.log.LogConfig$.validateNames(LogConfig.scala:137)
    at kafka.log.LogConfig$.validate(LogConfig.scala:145)
    at kafka.admin.TopicCommand$.parseTopicConfigsToBeAdded(TopicCommand.scala:171)
    at kafka.admin.TopicCommand$$anonfun$alterTopic$1.apply(TopicCommand.scala:95)
    at kafka.admin.TopicCommand$$anonfun$alterTopic$1.apply(TopicCommand.scala:93)
    at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:57)
    at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:43)
    at kafka.admin.TopicCommand$.alterTopic(TopicCommand.scala:93)
    at kafka.admin.TopicCommand$.main(TopicCommand.scala:52)
    at kafka.admin.TopicCommand.main(TopicCommand.scala)

log.retention.hours is a property of a broker which is used as a default value when a topic is created. When you change configurations of currently running topic using kafka-topics.sh, you should specify a topic-level property.

A topic-level property for log retention time is retention.ms.

From Topic-level configuration in Kafka 0.8.1 documentation:

• Property: retention.ms
• Default: 7 days
• Server Default Property: log.retention.minutes
• Description: This configuration controls the maximum time we will retain a log before we will discard old log segments to free up space if we are using the "delete" retention policy. This represents an SLA on how soon consumers must read their data.

So the correct command depends on the version. Up to 0.8.2 (although docs still show its use up to 0.10.1) use kafka-topics.sh --alter and after 0.10.2 (or perhaps from 0.9.0 going forward) use kafka-configs.sh --alter

$ bin/kafka-topics.sh --zookeeper zk.yoursite.com --alter --topic as-access --config retention.ms=86400000
 

You can check whether the configuration is properly applied with the following command.

$ bin/kafka-topics.sh --describe --zookeeper zk.yoursite.com --topic as-access

Then you will see something like below.

Topic:as-access  PartitionCount:3  ReplicationFactor:3  Configs:retention.ms=86400000