Moves creation of Supplier<CompletableFuture<BucketConfiguration>> to runtime.

This allows the configured application TaskExecutor bean to be passed to CompletableFuture.supplyAsync()

See gh-3983

Author: spencergibb

spring-cloud-gateway-server-webmvc/src/main/java/org/springframework/cloud/gateway/server/mvc/filter/Bucket4jFilterFunctions.java

@@ -30,14 +30,18 @@
 import io.github.bucket4j.distributed.proxy.AsyncProxyManager;
 
 import org.springframework.cloud.gateway.server.mvc.common.MvcUtils;
+import org.springframework.core.task.TaskExecutor;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.HttpStatusCode;
+import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 import org.springframework.web.servlet.function.HandlerFilterFunction;
 import org.springframework.web.servlet.function.ServerRequest;
 import org.springframework.web.servlet.function.ServerResponse;
 
+import static org.springframework.boot.autoconfigure.task.TaskExecutionAutoConfiguration.APPLICATION_TASK_EXECUTOR_BEAN_NAME;
+
 public abstract class Bucket4jFilterFunctions {
 
 	/**
@@ -66,8 +70,7 @@ public static HandlerFilterFunction<ServerResponse, ServerResponse> rateLimit(
 			Consumer<RateLimitConfig> configConsumer) {
 		RateLimitConfig config = new RateLimitConfig();
 		configConsumer.accept(config);
-		Supplier<CompletableFuture<BucketConfiguration>> configSupplier = () -> CompletableFuture
-			.supplyAsync(() -> config.configurationBuilder.apply(config));
+		Supplier<BucketConfiguration> bucketConfigurationSupplier = () -> config.configurationBuilder.apply(config);
 
 		return (request, next) -> {
 			AsyncProxyManager proxyManager = MvcUtils.getApplicationContext(request).getBean(AsyncProxyManager.class);
@@ -76,6 +79,9 @@ public static HandlerFilterFunction<ServerResponse, ServerResponse> rateLimit(
 				// TODO: configurable empty key status code
 				return ServerResponse.status(HttpStatus.FORBIDDEN).build();
 			}
+			TaskExecutor taskExecutor = MvcUtils.getApplicationContext(request).getBean(APPLICATION_TASK_EXECUTOR_BEAN_NAME, TaskExecutor.class);
+			Supplier<CompletableFuture<BucketConfiguration>> configSupplier = () -> CompletableFuture
+					.supplyAsync(bucketConfigurationSupplier, taskExecutor);
 			AsyncBucketProxy bucket = proxyManager.builder().build(key, configSupplier);
 			CompletableFuture<ConsumptionProbe> bucketFuture = bucket.tryConsumeAndReturnRemaining(config.getTokens());
 			ConsumptionProbe consumptionProbe;