Adds support for HttpClient eviction interval.

Fixes gh-2153
Fixes gh-2187

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@@ -17,6 +17,7 @@
 package org.springframework.cloud.gateway.config;
 
 import java.security.cert.X509Certificate;
+import java.time.Duration;
 import java.util.List;
 import java.util.Set;
 import java.util.function.Supplier;
@@ -663,21 +664,7 @@ public class GatewayAutoConfiguration {
 				List<HttpClientCustomizer> customizers) {
 
 			// configure pool resources
-			HttpClientProperties.Pool pool = properties.getPool();
-
-			ConnectionProvider connectionProvider;
-			if (pool.getType() == DISABLED) {
-				connectionProvider = ConnectionProvider.newConnection();
-			}
-			else if (pool.getType() == FIXED) {
-				connectionProvider = ConnectionProvider.fixed(pool.getName(),
-						pool.getMaxConnections(), pool.getAcquireTimeout(),
-						pool.getMaxIdleTime(), pool.getMaxLifeTime());
-			}
-			else {
-				connectionProvider = ConnectionProvider.elastic(pool.getName(),
-						pool.getMaxIdleTime(), pool.getMaxLifeTime());
-			}
+			ConnectionProvider connectionProvider = buildConnectionProvider(properties);
 
 			HttpClient httpClient = HttpClient.create(connectionProvider)
 					// TODO: move customizations to HttpClientCustomizers
@@ -778,6 +765,42 @@ public class GatewayAutoConfiguration {
 			return httpClient;
 		}
 
+		private ConnectionProvider buildConnectionProvider(
+				HttpClientProperties properties) {
+			HttpClientProperties.Pool pool = properties.getPool();
+
+			ConnectionProvider connectionProvider;
+			if (pool.getType() == DISABLED) {
+				connectionProvider = ConnectionProvider.newConnection();
+			}
+			else {
+				// create either Fixed or Elastic pool
+				ConnectionProvider.Builder builder = ConnectionProvider
+						.builder(pool.getName());
+				if (pool.getType() == FIXED) {
+					builder.maxConnections(pool.getMaxConnections())
+							.pendingAcquireMaxCount(-1).pendingAcquireTimeout(
+									Duration.ofMillis(pool.getAcquireTimeout()));
+				}
+				else {
+					// Elastic
+					builder.maxConnections(Integer.MAX_VALUE)
+							.pendingAcquireTimeout(Duration.ofMillis(0))
+							.pendingAcquireMaxCount(-1);
+				}
+
+				if (pool.getMaxIdleTime() != null) {
+					builder.maxIdleTime(pool.getMaxIdleTime());
+				}
+				if (pool.getMaxLifeTime() != null) {
+					builder.maxLifeTime(pool.getMaxLifeTime());
+				}
+				builder.evictInBackground(pool.getEvictionInterval());
+				connectionProvider = builder.build();
+			}
+			return connectionProvider;
+		}
+
 		@Bean
 		public HttpClientProperties httpClientProperties() {
 			return new HttpClientProperties();

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/config/HttpClientProperties.java

@@ -211,6 +211,12 @@ public class HttpClientProperties {
 		 */
 		private Duration maxLifeTime = null;
 
+		/**
+		 * Perform regular eviction checks in the background at a specified interval.
+		 * Disabled by default ({@link Duration#ZERO})
+		 */
+		private Duration evictionInterval = Duration.ZERO;
+
 		public PoolType getType() {
 			return type;
 		}
@@ -259,12 +265,20 @@ public class HttpClientProperties {
 			this.maxLifeTime = maxLifeTime;
 		}
 
+		public Duration getEvictionInterval() {
+			return evictionInterval;
+		}
+
+		public void setEvictionInterval(Duration evictionInterval) {
+			this.evictionInterval = evictionInterval;
+		}
+
 		@Override
 		public String toString() {
 			return "Pool{" + "type=" + type + ", name='" + name + '\''
 					+ ", maxConnections=" + maxConnections + ", acquireTimeout="
 					+ acquireTimeout + ", maxIdleTime=" + maxIdleTime + ", maxLifeTime="
-					+ maxLifeTime + '}';
+					+ maxLifeTime + ", evictionInterval=" + evictionInterval + '}';
 		}
 
 		public enum PoolType {

spring-cloud-gateway-server/src/test/java/org/springframework/cloud/gateway/config/GatewayAutoConfigurationTests.java

@@ -94,6 +94,7 @@ public class GatewayAutoConfigurationTests {
 						"spring.cloud.gateway.httpclient.ssl.use-insecure-trust-manager=true",
 						"spring.cloud.gateway.httpclient.connect-timeout=10",
 						"spring.cloud.gateway.httpclient.response-timeout=10s",
+						"spring.cloud.gateway.httpclient.pool.eviction-interval=10s",
 						"spring.cloud.gateway.httpclient.pool.type=fixed",
 						"spring.cloud.gateway.httpclient.compression=true",
 						// greather than integer max value
@@ -108,6 +109,7 @@ public class GatewayAutoConfigurationTests {
 					assertThat(properties.getMaxInitialLineLength().toBytes())
 							.isLessThanOrEqualTo(Integer.MAX_VALUE);
 					assertThat(properties.isCompression()).isEqualTo(true);
+					assertThat(properties.getPool().getEvictionInterval()).hasSeconds(10);
 					/*
 					 * FIXME: 2.1.0 HttpClientOptions options = httpClient.options();
 					 *