Add logging of cache ratio

Two reasons for logging this:

- to assist in sizing the ledger cache;
- to resolve the mystery when there appear to be no fetches from the penciller (as the penciller does not report fetches from the ledger cache)

src/leveled_bookie.erl

@@ -129,6 +129,7 @@
 -define(SNAPTIMEOUT_LONG, 43200). % 12 hours
 -define(SST_PAGECACHELEVEL_NOLOOKUP, 1).
 -define(SST_PAGECACHELEVEL_LOOKUP, 4).
+-define(CACHE_LOGPOINT, 100000).
 -define(OPTION_DEFAULTS,
             [{root_path, undefined},
                 {snapshot_bookie, undefined},
@@ -178,6 +179,7 @@
                 get_countdown = 0 :: integer(),
                 fold_countdown = 0 :: integer(),
                 head_countdown = 0 :: integer(),
+                cache_ratio = {0, 0} :: cache_ratio(),
                 get_timings = no_timing :: get_timings(),
                 put_timings = no_timing :: put_timings(),
                 fold_timings = no_timing :: fold_timings(),
@@ -210,6 +212,7 @@
 -type fold_timings() :: no_timing|#fold_timings{}.
 -type head_timings() :: no_timing|#head_timings{}.
 -type timing_types() :: head|get|put|fold.
+-type cache_ratio() :: {non_neg_integer(), non_neg_integer()}.
 
 
 -type open_options() :: 
@@ -1307,10 +1310,13 @@ handle_call({get, Bucket, Key, Tag}, _From, State)
                                         when State#state.head_only == false ->
     LedgerKey = leveled_codec:to_ledgerkey(Bucket, Key, Tag),
     SWh = os:timestamp(),
-    HeadResult = 
+    {H0, UpdCR} =
-        case fetch_head(LedgerKey,
+        fetch_head(LedgerKey,
                     State#state.penciller,
-                        State#state.ledger_cache) of
+                    State#state.ledger_cache,
+                    State#state.cache_ratio),
+    HeadResult = 
+        case H0 of
             not_present ->
                 not_found;
             Head ->
@@ -1348,14 +1354,17 @@ handle_call({get, Bucket, Key, Tag}, _From, State)
     {Timings, CountDown} = 
         update_statetimings(get, Timings2, State#state.get_countdown),
     {reply, Reply, State#state{get_timings = Timings, 
-                                get_countdown = CountDown}};
+                                get_countdown = CountDown,
+                                cache_ratio = maybelog_cacheratio(UpdCR)}};
 handle_call({head, Bucket, Key, Tag, SQNOnly}, _From, State) 
                                         when State#state.head_lookup == true ->
     SWp = os:timestamp(),
     LK = leveled_codec:to_ledgerkey(Bucket, Key, Tag),
-    Head =  fetch_head(LK, 
+    {Head, UpdCR} =
+        fetch_head(LK, 
                     State#state.penciller, 
                     State#state.ledger_cache,
+                    State#state.cache_ratio,
                     State#state.head_only),
     {SWr, UpdTimingsP} = 
             update_timings(SWp, {head, pcl}, State#state.head_timings),
@@ -1411,7 +1420,8 @@ handle_call({head, Bucket, Key, Tag, SQNOnly}, _From, State)
         Reply, 
         State#state{head_timings = UpdTimings,
                     head_countdown = CountDown,
-                    ink_checking = JournalCheckFrequency}};
+                    ink_checking = JournalCheckFrequency,
+                    cache_ratio = maybelog_cacheratio(UpdCR)}};
 handle_call({snapshot, SnapType, Query, LongRunning}, _From, State) ->
     % Snapshot the store, specifying if the snapshot should be long running 
     % (i.e. will the snapshot be queued or be required for an extended period 
@@ -2069,20 +2079,24 @@ scan_table(Table, StartKey, EndKey, Acc, MinSQN, MaxSQN) ->
     end.
 
 
--spec fetch_head(leveled_codec:ledger_key(), pid(), ledger_cache())
+-spec fetch_head(leveled_codec:ledger_key(), pid(), ledger_cache(),
-                                    -> not_present|leveled_codec:ledger_value().
+                    cache_ratio()) -> 
+                        {not_present|leveled_codec:ledger_value(),
+                            cache_ratio()}.
 %% @doc
 %% Fetch only the head of the object from the Ledger (or the bookie's recent
 %% ledger cache if it has just been updated).  not_present is returned if the 
 %% Key is not found
-fetch_head(Key, Penciller, LedgerCache) ->
+fetch_head(Key, Penciller, LedgerCache, CacheRatio) ->
-    fetch_head(Key, Penciller, LedgerCache, false).
+    fetch_head(Key, Penciller, LedgerCache, CacheRatio, false).
 
--spec fetch_head(leveled_codec:ledger_key(), pid(), ledger_cache(), boolean())
+-spec fetch_head(leveled_codec:ledger_key(), pid(), ledger_cache(),
-                                    -> not_present|leveled_codec:ledger_value().
+                    cache_ratio(), boolean())
+                        -> {not_present|leveled_codec:ledger_value(),
+                            cache_ratio()}.
 %% doc
 %% The L0Index needs to be bypassed when running head_only
-fetch_head(Key, Penciller, LedgerCache, HeadOnly) ->
+fetch_head(Key, Penciller, LedgerCache, {RC, CC}, HeadOnly) ->
     SW = os:timestamp(),
     CacheResult =
         case LedgerCache#ledger_cache.mem of
@@ -2093,7 +2107,7 @@ fetch_head(Key, Penciller, LedgerCache, HeadOnly) ->
         end,
     case CacheResult of
         [{Key, Head}] ->
-            Head;
+            {Head, {RC + 1, CC + 1}};
         [] ->
             Hash = leveled_codec:segment_hash(Key),
             UseL0Idx = not HeadOnly, 
@@ -2102,10 +2116,10 @@ fetch_head(Key, Penciller, LedgerCache, HeadOnly) ->
             case leveled_penciller:pcl_fetch(Penciller, Key, Hash, UseL0Idx) of
                 {Key, Head} ->
                     maybe_longrunning(SW, pcl_head),
-                    Head;
+                    {Head, {RC + 1, CC}};
                 not_present ->
                     maybe_longrunning(SW, pcl_head),
-                    not_present
+                    {not_present, {RC + 1, CC}}
             end
     end.
 
@@ -2436,6 +2450,13 @@ update_timings(SW, {fold, setup}, Timings) ->
     Timings0 = Timings#fold_timings{setup_time = FST, sample_count = CNT},
     {no_timing, Timings0}.
 
+
+-spec maybelog_cacheratio(cache_ratio()) -> cache_ratio().
+maybelog_cacheratio({?CACHE_LOGPOINT, CC}) ->
+    leveled_log:log("B0021", [?CACHE_LOGPOINT, CC]),
+    {0, 0};
+maybelog_cacheratio(CR) ->
+    CR.
 %%%============================================================================
 %%% Test
 %%%============================================================================

src/leveled_log.erl

@@ -80,6 +80,8 @@
     {"B0020",
         {warn, "Ratio of penciller cache size ~w to bookie's memory "
                     ++ "cache size ~w is larger than expected"}},
+    {"B0021",
+        {info, "Bookie fetch RequestCount=~w and CacheCount=~w"}},
 
     {"R0001",
         {debug, "Object fold to process batch of ~w objects"}},