Performance optimizations in ExecutionInterceptorChain (#4863)

1. Removed apply*Hack method. This method wasn't doing anything, because its side effects were immediately overridden.
2. Do not modify the execution context in the modify* methods unless the interceptor requests a modification. The time added by the comparisons are less than the cost of always modifying the interceptor context, because modifying the execution context is relatively rare.

core/sdk-core/src/main/java/software/amazon/awssdk/core/interceptor/ExecutionInterceptorChain.java

@@ -20,7 +20,6 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Objects;
-import java.util.Optional;
 import java.util.function.Consumer;
 import org.reactivestreams.Publisher;
 import software.amazon.awssdk.annotations.SdkProtectedApi;
@@ -29,8 +28,6 @@
 import software.amazon.awssdk.core.async.AsyncRequestBody;
 import software.amazon.awssdk.core.internal.interceptor.DefaultFailedExecutionContext;
 import software.amazon.awssdk.core.sync.RequestBody;
-import software.amazon.awssdk.http.ContentStreamProvider;
-import software.amazon.awssdk.http.SdkHttpFullRequest;
 import software.amazon.awssdk.http.SdkHttpRequest;
 import software.amazon.awssdk.http.SdkHttpResponse;
 import software.amazon.awssdk.utils.Logger;
@@ -66,9 +63,11 @@ public InterceptorContext modifyRequest(InterceptorContext context, ExecutionAtt
         InterceptorContext result = context;
         for (ExecutionInterceptor interceptor : interceptors) {
             SdkRequest interceptorResult = interceptor.modifyRequest(result, executionAttributes);
-            validateInterceptorResult(result.request(), interceptorResult, interceptor, "modifyRequest");
 
-            result = result.copy(b -> b.request(interceptorResult));
+            if (interceptorResult != result.request()) {
+                validateInterceptorResult(result.request(), interceptorResult, interceptor, "modifyRequest");
+                result = result.copy(b -> b.request(interceptorResult));
+            }
         }
         return result;
     }
@@ -88,46 +87,20 @@ public InterceptorContext modifyHttpRequestAndHttpContent(InterceptorContext con
             AsyncRequestBody asyncRequestBody = interceptor.modifyAsyncHttpContent(result, executionAttributes).orElse(null);
             RequestBody requestBody = interceptor.modifyHttpContent(result, executionAttributes).orElse(null);
             SdkHttpRequest interceptorResult = interceptor.modifyHttpRequest(result, executionAttributes);
-            validateInterceptorResult(result.httpRequest(), interceptorResult, interceptor, "modifyHttpRequest");
 
-            InterceptorContext.Builder builder = result.toBuilder();
+            if (asyncRequestBody != result.asyncRequestBody().orElse(null) ||
+                requestBody != result.requestBody().orElse(null) ||
+                interceptorResult != result.httpRequest()) {
 
-            applySdkHttpFullRequestHack(result, builder);
-
-            result = builder.httpRequest(interceptorResult)
-                            .asyncRequestBody(asyncRequestBody)
-                            .requestBody(requestBody)
-                            .build();
+                validateInterceptorResult(result.httpRequest(), interceptorResult, interceptor, "modifyHttpRequest");
+                result = result.copy(r -> r.httpRequest(interceptorResult)
+                                           .asyncRequestBody(asyncRequestBody)
+                                           .requestBody(requestBody));
+            }
         }
         return result;
     }
 
-    private void applySdkHttpFullRequestHack(InterceptorContext context, InterceptorContext.Builder builder) {
-        // Someone thought it would be a great idea to allow interceptors to return SdkHttpFullRequest to modify the payload
-        // instead of using the modifyPayload method. This is for backwards-compatibility with those interceptors.
-        // TODO: Update interceptors to use the proper payload-modifying method so that this code path is only used for older
-        // client versions. Maybe if we ever decide to break @SdkProtectedApis (if we stop using Jackson?!) we can even remove
-        // this hack!
-        SdkHttpFullRequest sdkHttpFullRequest = (SdkHttpFullRequest) context.httpRequest();
-
-        if (context.requestBody().isPresent()) {
-            return;
-        }
-
-        Optional<ContentStreamProvider> contentStreamProvider = sdkHttpFullRequest.contentStreamProvider();
-
-        if (!contentStreamProvider.isPresent()) {
-            return;
-        }
-
-        long contentLength = Long.parseLong(sdkHttpFullRequest.firstMatchingHeader("Content-Length").orElse("0"));
-        String contentType = sdkHttpFullRequest.firstMatchingHeader("Content-Type").orElse("");
-        RequestBody requestBody = RequestBody.fromContentProvider(contentStreamProvider.get(),
-                                                                  contentLength,
-                                                                  contentType);
-        builder.requestBody(requestBody);
-    }
-
     public void beforeTransmission(Context.BeforeTransmission context, ExecutionAttributes executionAttributes) {
         interceptors.forEach(i -> i.beforeTransmission(context, executionAttributes));
     }
@@ -143,11 +116,15 @@ public InterceptorContext modifyHttpResponse(InterceptorContext context,
         for (int i = interceptors.size() - 1; i >= 0; i--) {
             SdkHttpResponse interceptorResult =
                 interceptors.get(i).modifyHttpResponse(result, executionAttributes);
-            validateInterceptorResult(result.httpResponse(), interceptorResult, interceptors.get(i), "modifyHttpResponse");
-
             InputStream response = interceptors.get(i).modifyHttpResponseContent(result, executionAttributes).orElse(null);
 
-            result = result.toBuilder().httpResponse(interceptorResult).responseBody(response).build();
+            if (interceptorResult != result.httpResponse() || response != result.responseBody().orElse(null)) {
+                validateInterceptorResult(result.httpResponse(), interceptorResult, interceptors.get(i), "modifyHttpResponse");
+                result = result.copy(r -> r.httpResponse(interceptorResult)
+                                           .responseBody(response));
+            }
+
+
         }
 
         return result;
@@ -163,9 +140,9 @@ public InterceptorContext modifyAsyncHttpResponse(InterceptorContext context,
             Publisher<ByteBuffer> newResponsePublisher =
                 interceptor.modifyAsyncHttpResponseContent(result, executionAttributes).orElse(null);
 
-            result = result.toBuilder()
-                           .responsePublisher(newResponsePublisher)
-                           .build();
+            if (newResponsePublisher != result.responsePublisher().orElse(null)) {
+                result = result.copy(r -> r.responsePublisher(newResponsePublisher));
+            }
         }
 
         return result;
@@ -183,9 +160,11 @@ public InterceptorContext modifyResponse(InterceptorContext context, ExecutionAt
         InterceptorContext result = context;
         for (int i = interceptors.size() - 1; i >= 0; i--) {
             SdkResponse interceptorResult = interceptors.get(i).modifyResponse(result, executionAttributes);
-            validateInterceptorResult(result.response(), interceptorResult, interceptors.get(i), "modifyResponse");
 
-            result = result.copy(b -> b.response(interceptorResult));
+            if (interceptorResult != result.response()) {
+                validateInterceptorResult(result.response(), interceptorResult, interceptors.get(i), "modifyResponse");
+                result = result.copy(b -> b.response(interceptorResult));
+            }
         }
 
         return result;
@@ -200,8 +179,12 @@ public DefaultFailedExecutionContext modifyException(DefaultFailedExecutionConte
         DefaultFailedExecutionContext result = context;
         for (int i = interceptors.size() - 1; i >= 0; i--) {
             Throwable interceptorResult = interceptors.get(i).modifyException(result, executionAttributes);
-            validateInterceptorResult(result.exception(), interceptorResult, interceptors.get(i), "modifyException");
-            result = result.copy(b -> b.exception(interceptorResult));
+
+            if (interceptorResult != result.exception()) {
+                validateInterceptorResult(result.exception(), interceptorResult,
+                                          interceptors.get(i), "modifyException");
+                result = result.copy(b -> b.exception(interceptorResult));
+            }
         }
 
         return result;