perf: Create Ante/Post handler chain once.

ChainAnteDecorators and ChainPostDecorators would create the chaining handler on
each invocation repeatedly. This also had the code checking whether the terminator
was at the end of the chain.

Creating all the handlers upfront and only once improved the performance of `make test-sim-profile`
on my local machine from 133.2s to 132s for a ~1% performance improvement.

This is similar to #14164 but maintains the existing recursive behavior.

CHANGELOG.md

@@ -69,6 +69,7 @@ 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`.
 * (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.
 * (gov) [#15979](https://github.com/cosmos/cosmos-sdk/pull/15979) Improve gov error message when failing to convert v1 proposal to v1beta1.

types/handler.go

@@ -40,14 +40,18 @@ 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)
+	// Install the terminal AnteHandler.
+	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 +67,18 @@ 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)
+	// Install the terminal PostHandler.
+	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