[jira] [Updated] (KAFKA-3300) Calculate the initial/max size of offset index files and reduce the memory footprint for memory mapped index files.

["Ismael Juma (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-3300?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ismael Juma updated KAFKA-3300:
-------------------------------
    Fix Version/s:     (was: 0.11.0.0)
                   0.11.1.0

> Calculate the initial/max size of offset index files and reduce the memory footprint for memory mapped index files.
> -------------------------------------------------------------------------------------------------------------------
>
>                 Key: KAFKA-3300
>                 URL: https://issues.apache.org/jira/browse/KAFKA-3300
>             Project: Kafka
>          Issue Type: Improvement
>    Affects Versions: 0.9.0.1
>            Reporter: Jiangjie Qin
>            Assignee: Jiangjie Qin
>             Fix For: 0.11.1.0
>
>
> Currently the initial/max size of offset index file is configured by {{log.index.max.bytes}}. This will be the offset index file size for active log segment until it rolls out. 
> Theoretically, we can calculate the upper bound of offset index size using the following formula:
> {noformat}
> log.segment.bytes / index.interval.bytes * 8
> {noformat}
> With default setting the bytes needed for an offset index size is 1GB / 4K * 8 = 2MB. And the default log.index.max.bytes is 10MB.
> This means we are over-allocating at least 8MB on disk and mapping it to memory.
> We can probably do the following:
> 1. When creating a new offset index, calculate the size using the above formula,
> 2. If the result in (1) is greater than log.index.max.bytes, we allocate log.index.max.bytes instead.
> This should be able to significantly save memory if a broker has a lot of partitions on it.



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