[rabbitmq-discuss] RabbitMQ config file.

Matthew Sackman matthew at lshift.net
Thu May 13 14:52:38 BST 2010

Hi Radha,

On Tue, May 11, 2010 at 12:05:55PM +0530, Radha Krishnan D wrote:
> We are using rabbitmq-server-1.7.2  ( downloaded under the heading
> generic Linux ). Since our linux machine RAM is 8 GB and it is a 32 bit
> machine. RabbitMQ takes 1638 MB and it prints it in the logs. How ever
> when I want to increase the size by using   {rabbit,
> [{vm_memory_high_watermark,  2.0}]} the rabbitMQ server is not
> recognizing this configuration change  at all. 

Err, if you're using a 32-bit OS, it's not going to be able to allocate
more than 4GB to any single application. The 0.4 by default then looks
to be correct, as 1638/0.4 = 4095, i.e. 4GB.

The 0.4 is carefully chosen to accomodate the possibility of Erlang's GC
temporarily using up an awful lot more RAM. If you ever have the case
where Erlang runs out of address space then it will crash, and take down
Rabbit with it.

I believe from your subsequent email that you've sorted out the
configuration issue.

> Also please clear us about the difference between rabbitmq.conf file and
> rabbitmq.config file.

.conf is a shell file which should be used to set environment variables
which influence Rabbit. .config is an Erlang term file. Originally we
only had the .conf file. However as time passed, and we needed to allow
more complex configurations, the .config file came along (which is also
used for configuring plugins). Currently, it's a bit of a mess as some
things you can configure in either place, and others you can't. We have
a fairly high priority bug to unify, document and generally sort all of
this out.


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