Merge pull request #60 from paulo-ferraz-oliveira/fix/scheduler_usage

Don't throw an exception when erlang:statistics(scheduler_wall_time) …
apache · Oct 11, 2017 · 6e420aa · 6e420aa
2 parents a270acd + eb99031
commit 6e420aa
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Showing 2 changed files with 4 additions and 2 deletions.
diff --git a/src/recon.erl b/src/recon.erl
@@ -348,7 +348,7 @@ node_stats_print(N, Interval) ->
 %% </ul>
 %%
 %% A scheduler isn't busy when doing anything else.
--spec scheduler_usage(Millisecs) -> [{SchedulerId, Usage}] when
+-spec scheduler_usage(Millisecs) -> undefined | [{SchedulerId, Usage}] when
     Millisecs :: non_neg_integer(),
     SchedulerId :: pos_integer(),
     Usage :: number().

diff --git a/src/recon_lib.erl b/src/recon_lib.erl
@@ -212,12 +212,14 @@ time_fold(N, Interval, Fun, State, FoldFun, Init) ->
 
 %% @doc Diffs two runs of erlang:statistics(scheduler_wall_time) and
 %% returns usage metrics in terms of cores and 0..1 percentages.
--spec scheduler_usage_diff(SchedTime, SchedTime) -> [{SchedulerId, Usage}] when
+-spec scheduler_usage_diff(SchedTime, SchedTime) -> undefined | [{SchedulerId, Usage}] when
     SchedTime :: [{SchedulerId, ActiveTime, TotalTime}],
     SchedulerId :: pos_integer(),
     Usage :: number(),
     ActiveTime :: non_neg_integer(),
     TotalTime :: non_neg_integer().
+scheduler_usage_diff(First, Last) when First =:= undefined orelse Last =:= undefined ->
+    undefined;
 scheduler_usage_diff(First, Last) ->
     lists:map(
         fun ({{I, _A0, T}, {I, _A1, T}}) -> {I, 0.0}; % Avoid divide by zero