[rabbitmq-discuss] Config File Options

[Jason J. W. Williams]

Hi Matthew,

That helps a lot. Is msg_store_file_size_limit the maximum size of the
persistent store or the max size of the journal?

-J

On Mon, Sep 6, 2010 at 2:17 PM, Matthew Sackman <matthew at rabbitmq.com> wrote:
> On Mon, Sep 06, 2010 at 01:51:04PM -0600, Jason J. W. Williams wrote:
>> Thank you Matthew. That's very helpful. Are persister_max_wrap_entries
>> and persister_hibernate_after anything you'd want to tune for your
>> workload in the new persister?
>
> No, they're only for the old persister, not the new. The two that are
> relevant for the new persister are:
>
> msg_store_file_size_limit - this is the file size limit of the
> msg_store. The default is 16MB. Larger values will allow you to drive
> the disk faster, but GC will take longer.
>
> queue_index_max_journal_entries - this is the number of entries in queue
> journals before they get flushed out. Again, larger numbers will make
> better use of disk bandwidth at the expense of a larger interruption
> when journal scattering takes place.
>
> In both cases, if you're doing lots of short transactions, smaller
> numbers may help. The msg_store_file_size_limit is best tuned to the
> size of your messages, whilst queue_index_max_journal_entries is best
> tuned to the nature of your publications, regardless of size.
>
> If I sound vague, it's because we're yet to do any investigation into
> what workloads benefit best from what settings. Feel free to report your
> findings. Also, SSDs make a good improvement, especially when Rabbit is
> heavily loaded and doing transactions, or is very short of file
> descriptors.
>
>> Also, do you guys see any other Mnesia options besides
>> dump_log_write_threshold that usually need to be tuned for Rabbit?
>
> Rabbit only uses mnesia for exchange/binding/queue meta information. Not
> for messages. Thus unless you have a very high churn rate of those
> resources, you shouldn't need to tune it at all.
>
> Matthew
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