How to use ERL_MAX_PORTS and verify the setting in rabbitmq

[sakshiag]

We are moving to UBI9 for rabbitmq version 3.12. We read in the rabbitmq docs that UBI9 changed the default open file handlers to a huge number. That creates problems within Erlang. As a result the amount of file handlers should be configured lower. By adjusting ERL_MAX_PORTS to a certain number we can handle this.

Erlang Verison : 26.2
Rabbitmq Version : 3.12
Image :UBI9

We have two questions related to this :

1. How can we set ERL_MAX_PORTS as an environment variable. Is there any example to do this ?
2. How can we verify if it is using the set value ?



Can you please help us with the above queries?

[michaelklishin]

1. The same way you would set any other environment variable for any other process, including using systemd unit files if RabbitMQ is installed via an RPM. There is nothing RabbitMQ-specific
2. rabbitmq-diagnostics status and/or rabbitmqctl eval 'erlang:system_info(port_limit).'. Note that the limit will be set to the next power of 2, not to the exact ERL_MAX_PORTS value, so if set to 8191 it will actually be set to 8192, if set to 8193 it will actually be set to 16384, and so on

[michaelklishin]

If this is in response for this blog post, note that you have other options of controlling the open file handle limit on Linux, and on modern systemd-based distributions specifically.