Add config schema entry for total_memory_available_override_value

Closes #1445.

[#153501620]

(cherry picked from commit 314f68b)

Author: michaelklishin

docs/rabbitmq.conf.example

@@ -295,6 +295,10 @@
 ##
 # memory_monitor_interval = 2500
 
+## The total memory available can be calculated from the OS resources
+## - default option - or provided as a configuration parameter.
+# total_memory_available_override_value = 2GB
+
 ## Set disk free limit (in bytes). Once free disk space reaches this
 ## lower bound, a disk alarm will be set - see the documentation
 ## listed above for more details.

priv/schema/rabbit.schema

@@ -713,6 +713,11 @@ end}.
 {mapping, "vm_memory_calculation_strategy", "rabbit.vm_memory_calculation_strategy",
     [{datatype, {enum, [rss, erlang, allocated, legacy]}}]}.
 
+%% The total memory available can be calculated from the OS resources
+%% (default option) or provided as a configuration parameter
+{mapping, "total_memory_available_override_value", "rabbit.total_memory_available_override_value", [
+    {datatype, [integer, string]}]}.
+
 %% Set disk free limit (in bytes). Once free disk space reaches this
 %% lower bound, a disk alarm will be set - see the documentation
 %% listed above for more details.

test/config_schema_SUITE_data/rabbit.snippets

@@ -151,6 +151,14 @@ tcp_listen_options.exit_on_close = false",
   [{rabbit,
        [{vm_memory_calculation_strategy, legacy}]}],
   []},
+ {total_memory_available_override_value,
+  "total_memory_available_override_value = 1000000000",
+  [{rabbit,[{total_memory_available_override_value, 1000000000}]}],
+  []},
+ {total_memory_available_override_value_units,
+  "total_memory_available_override_value = 1024MB",
+  [{rabbit,[{total_memory_available_override_value, "1024MB"}]}],
+  []},
  {connection_max,
   "connection_max = 999",
   [{rabbit,[{connection_max, 999}]}],