[KAFKA-2589] Documentation bug: the default value for the "rebalance.backoff.ms" property is not specified correctly

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.8.2.1
• Fix Version/s: 0.9.0.1, 0.10.0.0
• Component/s: config
• Environment: any
• Assignee: Grant Henke
• Reporter: Bogdan Dimitriu
• Created: 28/Sep/15 15:37
• Updated: 05/Feb/16 21:25
• Resolved: 05/Feb/16 21:25

Description

The documentation for 0.8.2.1 consumer properties specifies:

rebalance.backoff.ms

2000

Backoff time between retries during rebalance

According to the source code though the default value is obtained this way:

val rebalanceBackoffMs = props.getInt("rebalance.backoff.ms", zkSyncTimeMs)

which is referenced from here:

val zkSyncTimeMs = props.getInt("zookeeper.sync.time.ms", 2000)

So by default it is 2000 as specified in the documentation, UNLESS the zookeeper.sync.time.ms is manually set to be different

This may create confusion with recommendations such:

In the case, make sure that rebalance.max.retries * rebalance.backoff.ms > zookeeper.session.timeout.ms

from here: https://cwiki.apache.org/confluence/display/KAFKA/FAQ#FAQ-Whyaretheremanyrebalancesinmyconsumerlog?