[rabbitmq-discuss] RabbitMQ-C library: channel_max

Emile Joubert emile at rabbitmq.com
Wed Oct 26 10:33:04 BST 2011

On 25/10/11 23:25, Pieter de Zwart wrote:
> Hey everyone,
> Dumb question alert, sorry. In the rabbitmq-c library, there are a few
> parameters to the amqp_login function that confuse me: channel_max and
> frame_max. Are these essentially the global QOS settings (how many
> channels can be on this connection, 0 being unlimited AND maximum window
> frame size, within which the client will try to tune the connection)?
> What are legitimate values for these? Should I expose them in the PHP
> extension, and allow people to change them prior to connecting?

You can find details of those parameters here:

Specifies highest channel number that the server permits.

The largest frame size that the server proposes for the connection

Zero is a good default for both on the client, meaning no limit. The
protocol specifies a minimum frame-max of 4kb, and the server will
suggest a default of 128kb, but this can be changed in the configuration
file - see details for the frame_max variable here:
http://www.rabbitmq.com/configure.html#config-items .

It is reasonable to expose these in the client. See the
ConnectionFactory classes in the rabbit Java and .net clients for a
possible way of doing so.


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