Add ability to define extra arguments for erlang

This implements new variable  rabbitmq_erlang_extra_args that enable
deployers to define extra flags for erlang [1]

[1] https://www.rabbitmq.com/runtime.html#cpu-reduce-idle-usage

Change-Id: Ibb0963962d6c7483d54fac69960910c0b13802a5

defaults/main.yml

@@ -226,6 +226,10 @@ rabbitmq_process_limit: 1048576
 # Limit memory consumption of the erlang VM
 rabbitmq_memory_high_watermark: 0.2
 
+# Extra arguments passed to Erlang on startup
+# rabbitmq_erlang_extra_args: "+sbwt none +sbwtdcpu none +sbwtdio none +stbt nnts"
+rabbitmq_erlang_extra_args: ""
+
 # RabbitMQ collect statistics interval
 rabbitmq_collect_statistics_interval: 5000
 

releasenotes/notes/erlang_extra_args-bba75332abeabd3e.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Added variable ``rabbitmq_erlang_extra_args`` that allows to define
+    extra arguments for erlang.

templates/rabbitmq-env.j2

@@ -4,3 +4,7 @@
 NODENAME=rabbit@{{ ansible_facts['hostname'] }}
 RABBITMQ_IO_THREAD_POOL_SIZE={{ rabbitmq_async_threads }}
 RABBITMQ_SERVER_ERL_ARGS="+P {{ rabbitmq_process_limit }}"
+
+{% if rabbitmq_erlang_extra_args %}
+RABBITMQ_SERVER_ADDITIONAL_ERL_ARGS="{{ rabbitmq_erlang_extra_args }}"
+{% endif %}