Support get / set_check_interval and simplify starting.

2 files changed, 42 insertions, 28 deletions

diff --git a/src/rabbit_alarm.erl b/src/rabbit_alarm.erl
index 5a19aca0..f66aefd0 100644
--- a/src/rabbit_alarm.erl
+++ b/src/rabbit_alarm.erl
@@ -74,33 +74,32 @@ start() ->
                     %% we can add our alarm_handler before memsup is
                     %% running, thus ensuring that we notice memory
                     %% alarms that go off on startup.
-                    {ok, _} = start_memsup(memsup),
-
-                    %% The default memsup check interval is 1 minute,
-                    %% which is way too long - rabbit can gobble up
-                    %% all memory in a matter of seconds.
-                    %% Unfortunately the memory_check_interval
-                    %% configuration parameter and
-                    %% memsup:set_check_interval/1 function only
-                    %% provide a granularity of minutes. So we have to
-                    %% peel off one layer of the API to get to the
-                    %% underlying layer which operates at the
-                    %% granularity of milliseconds.
-                    %%
-                    %% Note that the new setting will only take effect
-                    %% after the first check has completed, i.e. after
-                    %% one minute. So if rabbit eats all the memory
-                    %% within the first minute after startup then we
-                    %% are out of luck.
-                    ok = os_mon:call(
-                           memsup,
-                           {set_check_interval, ?MEMSUP_CHECK_INTERVAL},
-                           infinity)
+                    {ok, _} = start_memsup(memsup)
             end,
             ok;
         _ ->
             ok
-    end.
+    end,
+    %% The default memsup check interval is 1 minute,
+    %% which is way too long - rabbit can gobble up
+    %% all memory in a matter of seconds.
+    %% Unfortunately the memory_check_interval
+    %% configuration parameter and
+    %% memsup:set_check_interval/1 function only
+    %% provide a granularity of minutes. So we have to
+    %% peel off one layer of the API to get to the
+    %% underlying layer which operates at the
+    %% granularity of milliseconds.
+    %%
+    %% Note that the new setting will only take effect
+    %% after the first check has completed, i.e. after
+    %% one minute. So if rabbit eats all the memory
+    %% within the first minute after startup then we
+    %% are out of luck.
+    ok = os_mon:call(
+           memsup,
+           {set_check_interval, ?MEMSUP_CHECK_INTERVAL},
+           infinity).
 
 stop() ->
     ok = alarm_handler:delete_alarm_handler(?MODULE).
diff --git a/src/rabbit_memsup_linux.erl b/src/rabbit_memsup_linux.erl
index c9ff1c91..5e998dce 100644
--- a/src/rabbit_memsup_linux.erl
+++ b/src/rabbit_memsup_linux.erl
@@ -36,9 +36,9 @@
 
 -define(SERVER, memsup). %% must be the same as the standard memsup
 
--define(MEMORY_CHECK_INTERVAL, 1000).
+-define(DEFAULT_MEMORY_CHECK_INTERVAL, 1000).
 
--record(state, {memory_fraction, alarmed}).             
+-record(state, {memory_fraction, alarmed, timeout, timer}).             
 
 %%----------------------------------------------------------------------------
 
@@ -53,9 +53,15 @@ update() ->
 
 init(_Args) -> 
     Fraction = os_mon:get_env(memsup, system_memory_high_watermark),
-    {ok, _Tref} = timer:apply_interval(?MEMORY_CHECK_INTERVAL,
-                                       ?MODULE, update, []),
-    {ok, #state{alarmed = false, memory_fraction = Fraction}}.
+    TRef = start_timer(?DEFAULT_MEMORY_CHECK_INTERVAL),
+    {ok, #state{alarmed = false, 
+                memory_fraction = Fraction, 
+                timeout = ?DEFAULT_MEMORY_CHECK_INTERVAL,
+                timer = TRef}}.
+
+start_timer(Timeout) ->
+    {ok, TRef} = timer:apply_interval(Timeout, ?MODULE, update, []),
+    TRef.
 
 %% Export the same API as the real memsup. Note that
 %% get_sysmem_high_watermark gives an int in the range 0 - 100, while
@@ -66,6 +72,15 @@ handle_call(get_sysmem_high_watermark, _From, State) ->
 handle_call({set_sysmem_high_watermark, Float}, _From, State) ->
     {reply, ok, State#state{memory_fraction=Float}};
 
+handle_call(get_check_interval, _From, State) ->
+    {reply, State#state.timeout, State};
+
+handle_call({set_check_interval, Timeout}, _From, State = #state{timer = OldTRef}) ->
+    {ok, cancel} = timer:cancel(OldTRef),
+    NewTRef = start_timer(Timeout),
+    {reply, ok, State#state{timeout = Timeout,
+                            timer = NewTRef}};
+
 handle_call(_Request, _From, State) -> 
     {noreply, State}.