Detect version of os_mon, and if we have version > 2.2.1 then we trust its output

2 files changed, 55 insertions, 6 deletions

diff --git a/src/rabbit_misc.erl b/src/rabbit_misc.erl
index 172e27f4..2add5afb 100644
--- a/src/rabbit_misc.erl
+++ b/src/rabbit_misc.erl
@@ -56,6 +56,7 @@
 -export([format_stderr/2]).
 -export([start_applications/1, stop_applications/1]).
 -export([unfold/2, ceil/1, queue_fold/3]).
+-export([version_compare/2, version_compare/3]).
 
 -import(mnesia).
 -import(lists).
@@ -499,3 +500,36 @@ queue_fold(Fun, Init, Q) ->
         {empty, _Q}      -> Init;
         {{value, V}, Q1} -> queue_fold(Fun, Fun(V, Init), Q1)
     end.
+
+version_compare(A, B, lte) ->
+    case version_compare(A, B) of
+        eq -> true;
+        lt -> true;
+        gt -> false
+    end;
+version_compare(A, B, gte) ->
+    case version_compare(A, B) of
+        eq -> true;
+        gt -> true;
+        lt -> false
+    end;
+version_compare(A, B, Result) ->
+    Result =:= version_compare(A, B).
+
+version_compare([], []) ->
+    eq;
+version_compare([], _ ) ->
+    lt; %% 2.3 < 2.3.1
+version_compare(_ , []) ->
+    gt; %% 2.3.1 > 2.3
+version_compare(A,  B) ->
+    {AStr, ATl} = lists:splitwith(fun (X) -> X =/= $. end, A),
+    {BStr, BTl} = lists:splitwith(fun (X) -> X =/= $. end, B),
+    ANum = list_to_integer(AStr),
+    BNum = list_to_integer(BStr),
+    if ANum =:= BNum -> ATl1 = lists:dropwhile(fun (X) -> X =:= $. end, ATl),
+                        BTl1 = lists:dropwhile(fun (X) -> X =:= $. end, BTl),
+                        version_compare(ATl1, BTl1);
+       ANum < BNum   -> lt;
+       ANum > BNum   -> gt
+    end.
diff --git a/src/vm_memory_monitor.erl b/src/vm_memory_monitor.erl
index 02bd0499..0cdb4142 100644
--- a/src/vm_memory_monitor.erl
+++ b/src/vm_memory_monitor.erl
@@ -261,14 +261,29 @@ get_total_memory({unix,freebsd}) ->
     PageCount * PageSize;
 
 get_total_memory({win32,_OSname}) ->
-    %% Due to the Erlang print format bug, on Windows boxes the memory size is
-    %% broken. For example Windows 7 64 bit with 4Gigs of RAM we get negative
-    %% memory size:
+    %% Due to the Erlang print format bug, on Windows boxes the memory
+    %% size is broken. For example Windows 7 64 bit with 4Gigs of RAM
+    %% we get negative memory size:
     %% > os_mon_sysinfo:get_mem_info().
     %% ["76 -1658880 1016913920 -1 -1021628416 2147352576 2134794240\n"]
-    %% Due to this bug, we don't actually know anything. Even if the number is
-    %% postive we can't be sure if it's correct.
-    unknown;
+    %% Due to this bug, we don't actually know anything. Even if the
+    %% number is postive we can't be sure if it's correct. This only
+    %% affects us on os_mon versions prior to 2.2.1.
+    case application:get_key(os_mon, vsn) of
+        undefined ->
+            unknown;
+        {ok, Version} ->
+            case rabbit_misc:version_compare(Version, "2.2.1", lt) of
+                true -> %% os_mon is < 2.2.1, so we know nothing
+                    unknown;
+                false ->
+                    [Result|_] = os_mon_sysinfo:get_mem_info(),
+                    {ok, [_MemLoad, TotPhys, _AvailPhys,
+                          _TotPage, _AvailPage, _TotV, _AvailV], _RestStr} =
+                        io_lib:fread("~d~d~d~d~d~d~d", Result),
+                    TotPhys
+            end
+    end;
 
 get_total_memory({unix, linux}) ->
     File = read_proc_file("/proc/meminfo"),