Re: [PR] PoC Couch Stats Resource Tracker for tracking process local resource usage [couchdb]

["pgj (via GitHub)" <gi...@apache.org>]

pgj commented on code in PR #4812:
URL: https://github.com/apache/couchdb/pull/4812#discussion_r1413085196


##########
src/rexi/src/rexi.erl:
##########
@@ -328,3 +336,23 @@ drain_acks(Count) ->
     after 0 ->
         {ok, Count}
     end.
+
+get_delta() ->
+    {delta, couch_stats_resource_tracker:make_delta()}.
+
+maybe_add_delta(T) ->
+    case couch_stats_resource_tracker:is_enabled() of
+        false ->
+            T;
+        true ->
+            add_delta(T, get_delta())
+    end.
+
+add_delta({A}, Delta) -> {A, Delta};

Review Comment:
   The same could be expressed with the help of `erlang:insert_element/3` and `erlang:size/1`:
   
   ```erlang
   add_delta(T, Delta) -> erlang:insert_element(erlang:size(T) + 1, T, Delta).
   ```
   
   If maximum tuple size matters (semantically equivalent):
   
   ```erlang
   add_delta(T, Delta) when 0 < erlang:size(T), erlang:size(T) < 8 ->
       erlang:insert_element(erlang:size(T) + 1, T, Delta);
   add_delta(T, _Delta) -> T.
   ```



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