perf: Create Ante/Post handler chain once. (#16076)

Co-authored-by: Aleksandr Bezobchuk <alexanderbez@users.noreply.github.com>

CHANGELOG.md

@@ -70,6 +70,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 
 ### Improvements
 
+* (types) [#16076](https://github.com/cosmos/cosmos-sdk/pull/16076) Optimize `ChainAnteDecorators`/`ChainPostDecorators` to instantiate the functions once instead of on every invocation of the returned `AnteHandler`/`PostHandler`.
 * (client) [#16075](https://github.com/cosmos/cosmos-sdk/pull/16075) Partly revert [#15953](https://github.com/cosmos/cosmos-sdk/issues/15953) and `factory.Prepare` does nothing in offline mode.
 * (server) [#16071](https://github.com/cosmos/cosmos-sdk/pull/16071) When `mempool.max-txs` is set to a negative value, use a no-op mempool (effectively disable the app mempool).
 * (simapp) [#15958](https://github.com/cosmos/cosmos-sdk/pull/15958) Refactor SimApp for removing the global basic manager.

types/handler.go

@@ -40,14 +40,19 @@ func ChainAnteDecorators(chain ...AnteDecorator) AnteHandler {
 		return nil
 	}
 
-	// handle non-terminated decorators chain
-	if (chain[len(chain)-1] != Terminator{}) {
-		chain = append(chain, Terminator{})
+	handlerChain := make([]AnteHandler, len(chain)+1)
+	// set the terminal AnteHandler decorator
+	handlerChain[len(chain)] = func(ctx Context, tx Tx, simulate bool) (Context, error) {
+		return ctx, nil
 	}
-
-	return func(ctx Context, tx Tx, simulate bool) (Context, error) {
-		return chain[0].AnteHandle(ctx, tx, simulate, ChainAnteDecorators(chain[1:]...))
+	for i := 0; i < len(chain); i++ {
+		ii := i
+		handlerChain[ii] = func(ctx Context, tx Tx, simulate bool) (Context, error) {
+			return chain[ii].AnteHandle(ctx, tx, simulate, handlerChain[ii+1])
+		}
 	}
+
+	return handlerChain[0]
 }
 
 // ChainPostDecorators chains PostDecorators together with each PostDecorator
@@ -63,14 +68,18 @@ func ChainPostDecorators(chain ...PostDecorator) PostHandler {
 		return nil
 	}
 
-	// handle non-terminated decorators chain
-	if (chain[len(chain)-1] != Terminator{}) {
-		chain = append(chain, Terminator{})
+	handlerChain := make([]PostHandler, len(chain)+1)
+	// set the terminal PostHandler decorator
+	handlerChain[len(chain)] = func(ctx Context, tx Tx, simulate, success bool) (Context, error) {
+		return ctx, nil
 	}
-
-	return func(ctx Context, tx Tx, simulate, success bool) (Context, error) {
-		return chain[0].PostHandle(ctx, tx, simulate, success, ChainPostDecorators(chain[1:]...))
+	for i := 0; i < len(chain); i++ {
+		ii := i
+		handlerChain[ii] = func(ctx Context, tx Tx, simulate, success bool) (Context, error) {
+			return chain[ii].PostHandle(ctx, tx, simulate, success, handlerChain[ii+1])
+		}
 	}
+	return handlerChain[0]
 }
 
 // Terminator AnteDecorator will get added to the chain to simplify decorator code