[Other] erlang is built differently in 4.0.2 and 4.0.4 docker images

[rstrlcpy]

Community Support Policy

• I have read RabbitMQ's Community Support Policy

RabbitMQ version used

4.0.[2,3,4]

How is RabbitMQ deployed?

Community Docker image

Steps to reproduce the behavior in question

Hello.
I noticed Erlang in 4.0.4 docker image was build with USE_SELECT while 4.0.2 was build build without the flag. Could someone explain why?
Because of that 4.0.4 uses select as fallback-pollset while 4.0.2 uses poll and that causes warnings on UI because FDs limit is 1024 for the select.

4.0.4

$ docker run --rm -it rabbitmq:4.0.4-management-alpine /bin/bash
# echo "erlang:system_info(compile_info)." | erl | egrep -o "define USE_SELECT 1"
# define USE_SELECT 1
# 1

# echo "erlang:system_info(check_io)." | erl
Erlang/OTP 27 [erts-15.2] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [jit:ns]

Eshell V15.2 (press Ctrl+G to abort, type help(). for help)
1> [[{name,erts_poll},
  {primary,select},    <<<<<<<<<<<
  {kernel_poll,false},
  {memory_size,13448},
  {total_poll_set_size,1},
  {lazy_updates,true},
  {pending_updates,0},
  {batch_updates,false},
  {concurrent_updates,false},
  {fallback,true},
  {max_fds,1024},    <<<<<<<<<<<<
  {active_fds,0},
  {poll_threads,0}],

4.0.2

$ docker run --rm -it rabbitmq:4.0.2-management-alpine /bin/bash
# echo "erlang:system_info(compile_info)." | erl | egrep -o "define USE_SELECT 1"
# 0

# echo "erlang:system_info(check_io)." | erl
Erlang/OTP 26 [erts-14.2.5.4] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [jit]

Eshell V14.2.5.4 (press Ctrl+G to abort, type help(). for help)
1> [[{name,erts_poll},
  {primary,poll}, <<<<<<<<<<<<<<
  {kernel_poll,false},
  {memory_size,25240},
  {total_poll_set_size,1},
  {lazy_updates,true},
  {pending_updates,0},
  {batch_updates,false},
  {concurrent_updates,false},
  {fallback,true},
  {max_fds,1048576},   <<<<<<<<<<<<<<<<
  {active_fds,0},
  {poll_threads,0}],

4.0.3

$ docker run --rm -it rabbitmq:4.0.2-management-alpine /bin/bash
# echo "erlang:system_info(compile_info)." | erl | egrep -o "define USE_SELECT 1"
# 0

echo "erlang:system_info(check_io)." | erl
Erlang/OTP 26 [erts-14.2.5.4] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [jit]

Eshell V14.2.5.4 (press Ctrl+G to abort, type help(). for help)
1> [[{name,erts_poll},
  {primary,poll},     <<<<<<<<<<<<<<<<
  {kernel_poll,false},
  {memory_size,25240},
  {total_poll_set_size,1},
  {lazy_updates,true},
  {pending_updates,0},
  {batch_updates,false},
  {concurrent_updates,false},
  {fallback,true},
  {max_fds,1048576},    <<<<<<<<<<<<<<<<
  {active_fds,0},
  {poll_threads,0}],

[lukebakken]

Hello, thanks for using RabbitMQ.

Team RabbitMQ does not maintain the community docker image, though we do contribute to it. Please ask your question here:

https://github.com/docker-library/rabbitmq/discussions