Get statistics from Riak

Riak uses folsom_metrics to gather stats. For instance, to obtain GET and PUT operations speed

erl -name tst -remsh dev1@127.0.0.1 -setcookie riak

(dev1@127.0.0.1)1> folsom_metrics:get_histogram_statistics({riak_kv,node_get_fsm_time}).
[{min,4717},
{max,8996},
{arithmetic_mean,7383.6},
{geometric_mean,7212.3111343349},
{harmonic_mean,7027.752380931542},
{median,7322},
{variance,2550850.2666666666},
{standard_deviation,1597.1381488984184},
{skewness,-0.4278090078808716},
{kurtosis,-1.5957932734122735},
{percentile,[{75,8726},{95,8996},{99,8996},{999,8996}]},
{histogram,[{7317,4},{10717,6},{12717,0}]}]

(dev1@127.0.0.1)2> folsom_metrics:get_histogram_statistics({riak_kv,node_put_fsm_time}).
[{min,6377},
{max,15908},
{arithmetic_mean,11016.857142857143},
{geometric_mean,10642.075761157581},
{harmonic_mean,10268.560398236386},
{median,10245},
{variance,8786965.516483517},
{standard_deviation,2964.281618956525},
{skewness,0.1986125638310398},
{kurtosis,-1.3191900349579302},
{percentile,[{75,14016},{95,14995},{99,15908},{999,15908}]},
{histogram,[{11377,9},{15377,4},{19377,1}]}]

Note

• all values are in microseconds;
• stats are stored for last minute only;
• data is stored in memory (in ets tables), minimal impact on performance.

There was a task to gather stats about backend speed (leveldb and bitcask). Unfortunately Riak doesn't have such stats. To add them use patch below

diff --git a/src/riak_kv_stat.erl b/src/riak_kv_stat.erl
index 6cd5240..cf06de8 100644
--- a/src/riak_kv_stat.erl
+++ b/src/riak_kv_stat.erl
@@ -250,6 +250,8 @@ update1({get_fsm, Bucket, Microsecs, undefined, undefined, PerBucket}) ->
     folsom_metrics:notify_existing_metric({?APP, node_gets}, 1, spiral),
     folsom_metrics:notify_existing_metric({?APP, node_get_fsm_time}, Microsecs, histogram),
     do_get_bucket(PerBucket, {Bucket, Microsecs, undefined, undefined});
+update1({get_vnode, Microsecs}) ->
+    folsom_metrics:notify_existing_metric({?APP, vnode_get_time}, Microsecs, histogram);
 update1({get_fsm, Bucket, Microsecs, NumSiblings, ObjSize, PerBucket}) ->
     folsom_metrics:notify_existing_metric({?APP, node_gets}, 1, spiral),
     folsom_metrics:notify_existing_metric({?APP, node_get_fsm_time}, Microsecs, histogram),
@@ -260,6 +262,8 @@ update1({put_fsm_time, Bucket,  Microsecs, PerBucket}) ->
     folsom_metrics:notify_existing_metric({?APP, node_puts}, 1, spiral),
     folsom_metrics:notify_existing_metric({?APP, node_put_fsm_time}, Microsecs, histogram),
     do_put_bucket(PerBucket, {Bucket, Microsecs});
+update1({put_vnode, Microsecs}) ->
+    folsom_metrics:notify_existing_metric({?APP, vnode_put_time}, Microsecs, histogram);
 update1(read_repairs) ->
     folsom_metrics:notify_existing_metric({?APP, read_repairs}, 1, spiral);
 update1(coord_redir) ->
@@ -370,8 +374,10 @@ stats() ->
      {node_get_fsm_siblings, histogram},
      {node_get_fsm_objsize, histogram},
      {node_get_fsm_time, histogram},
+     {vnode_get_time, histogram},
      {node_puts, spiral},
      {node_put_fsm_time, histogram},
+     {vnode_put_time, histogram},
      {read_repairs, spiral},
      {coord_redirs_total, counter},
      {mapper_count, counter},
diff --git a/src/riak_kv_vnode.erl b/src/riak_kv_vnode.erl
index 0c1d761..8482548 100644
--- a/src/riak_kv_vnode.erl
+++ b/src/riak_kv_vnode.erl
@@ -760,8 +760,12 @@ perform_put({true, Obj},
                      reqid=ReqID,
                      index_specs=IndexSpecs}) ->
     Val = term_to_binary(Obj),
+    StartNow = now(),
     case Mod:put(Bucket, Key, IndexSpecs, Val, ModState) of
         {ok, UpdModState} ->
+            EndNow = now(),
+            Microsecs = timer:now_diff(EndNow, StartNow),
+            riak_kv_stat:update({put_vnode, Microsecs}),
             case RB of
                 true ->
                     Reply = {dw, Idx, Obj, ReqID};
@@ -866,7 +870,12 @@ do_get_term(BKey, Mod, ModState) ->
     end.
 
 do_get_binary({Bucket, Key}, Mod, ModState) ->
-    Mod:get(Bucket, Key, ModState).
+    StartNow = now(),
+    Res = Mod:get(Bucket, Key, ModState),
+    EndNow = now(),
+    Microsecs = timer:now_diff(EndNow, StartNow),
+    riak_kv_stat:update({get_vnode, Microsecs}),
+    Res.
 
 %% @private
 %% @doc This is a generic function for operations that involve

And now

(dev1@127.0.0.1)1> folsom_metrics:get_histogram_statistics({riak_kv,vnode_get_time}).
[{min,1516},
{max,5511},
{arithmetic_mean,3751.9},
{geometric_mean,3486.0111678580415},
{harmonic_mean,3190.229915515953},
{median,3892},
{variance,1879300.7666666668},
{standard_deviation,1370.8759122060126},
{skewness,-0.2710851221084366},
{kurtosis,-1.6493136210655186},
{percentile,[{75,4760},{95,5511},{99,5511},{999,5511}]},
{histogram,[{3816,4},{6516,6},{8516,0}]}]

(dev1@127.0.0.1)2> folsom_metrics:get_histogram_statistics({riak_kv,vnode_put_time}).
[{min,507},
{max,1776},
{arithmetic_mean,952.6428571428571},
{geometric_mean,818.2293396377823},
{harmonic_mean,722.2652885738648},
{median,561},
{variance,317468.09340659337},
{standard_deviation,563.4430702445397},
{skewness,0.5582974538827159},
{kurtosis,-1.7588827239013622},
{percentile,[{75,1615},{95,1759},{99,1776},{999,1776}]},
{histogram,[{1407,9},{2207,5},{3007,0}]}]

Also note that with n_val=3 1 PUT for Riak equals to (1 GET + 1 PUT) * 3 nodes for leveldb/bitcask. And 1 GET for Riak equals to 1 GET * 3 nodes for leveldb/bitcask.