[rabbitmq-discuss] problem about flow control and HA cluster

[bupt bupt]

thank you very much![?]


2013/5/30 Emile Joubert <emile at rabbitmq.com>

>
>
> Hi,
>
> On 27/05/13 16:12, bupt bupt wrote:
> > 1. Can you give me an example(internet address is ok) about how to
> > finish flow control if the length of queue is too big or if the used
> > memory and disc near the threshold. Can you give me some client
> > code(python or Java) to help me use it.
>
> If I understand correctly you have a broker with disk free space close
> to the disk free limit or memory use close to the high watermark, and
> you want to disable resource flow control.
>
> You should be aware that disabling resource flow control will make the
> broker more likely to run out of resources and crash. A better solution
> is to provision the broker with more resources. You should only relax
> the resource limits if your application can tolerate the increased risk
> of a crashing broker.
>
> You can relax memory flow control by increasing the memory high
> watermark from 40% to 50% or higher, e.g.
>
>  rabbitmqctl set_vm_memory_high_watermark 0.5
>
> Setting it to an infeasibly large ration effectively disables memory
> flow control:
>
>  rabbitmqctl set_vm_memory_high_watermark 100.0
>
> These instructions will change the limits for a running broker. See the
> instructions here for how to make the changes permanent by changing the
> configuration file: http://www.rabbitmq.com/memory.html#memsup
>
>
> You can reduce the disk free limit by specifying a lower limit:
>
>  rabbitmqctl eval 'rabbit_disk_monitor:set_disk_free_limit(500000000).'
>
> or disable it by setting the limit to zero:
>
>  rabbitmqctl eval 'rabbit_disk_monitor:set_disk_free_limit(0).'
>
> See http://www.rabbitmq.com/memory.html#diskfreesup for persisting the
> change in the configuration file.
>
>
> > 2. I have read document about how to set up rabbitmq cluster
> > by"http://www.rabbitmq.com/clustering.html" But who is master and who is
> > cluster, It  doesn't tell us. which broker manage all the nodes in
> > cluster? I didn't see any mirror queue in this address, Can this cluster
> > still be HA cluster?
>
> There is no global master. Queues can have different policies, so there
> is a master node per queue (assuming the queue is mirrored). See the
> "rabbitmqctl list_queues" documentation for querying the master and
> slave nodes for queues:
>
> http://www.rabbitmq.com/man/rabbitmqctl.1.man.html
>
> > 3. Is every message has length and size limit? what is the maximum size
> > of every message?
>
>
> Messages can be as large as you like, but they should not consume a
> significant fraction of total available RAM. If you want to process
> extremely large messages then you need alot of RAM.
>
> Queue length can be limited with the x-max-length argument. See
> http://www.rabbitmq.com/maxlength.html.
>
>
>
>
> -Emile
>
>
>
>
>
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