Adds configurable maxLifeTime in HttpClientProperties.

fixes gh-1542

docs/src/main/asciidoc/_configprops.adoc

@@ -30,6 +30,7 @@
 |spring.cloud.gateway.httpclient.pool.acquire-timeout |  | Only for type FIXED, the maximum time in millis to wait for aquiring.
 |spring.cloud.gateway.httpclient.pool.max-connections |  | Only for type FIXED, the maximum number of connections before starting pending acquisition on existing ones.
 |spring.cloud.gateway.httpclient.pool.max-idle-time |  | Time in millis after which the channel will be closed. If NULL, there is no max idle time.
+|spring.cloud.gateway.httpclient.pool.max-life-time |  | Duration after which the channel will be closed. If NULL, there is no max life time.
 |spring.cloud.gateway.httpclient.pool.name | proxy | The channel pool map name, defaults to proxy.
 |spring.cloud.gateway.httpclient.pool.type |  | Type of pool for HttpClient to use, defaults to ELASTIC.
 |spring.cloud.gateway.httpclient.proxy.host |  | Hostname for proxy configuration of Netty HttpClient.

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

@@ -591,11 +591,11 @@ public class GatewayAutoConfiguration {
 			else if (pool.getType() == FIXED) {
 				connectionProvider = ConnectionProvider.fixed(pool.getName(),
 						pool.getMaxConnections(), pool.getAcquireTimeout(),
-						pool.getMaxIdleTime());
+						pool.getMaxIdleTime(), pool.getMaxLifeTime());
 			}
 			else {
 				connectionProvider = ConnectionProvider.elastic(pool.getName(),
-						pool.getMaxIdleTime());
+						pool.getMaxIdleTime(), pool.getMaxLifeTime());
 			}
 
 			HttpClient httpClient = HttpClient.create(connectionProvider)

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

@@ -178,6 +178,12 @@ public class HttpClientProperties {
 		 */
 		private Duration maxIdleTime = null;
 
+		/**
+		 * Duration after which the channel will be closed. If NULL, there is no max life
+		 * time.
+		 */
+		private Duration maxLifeTime = null;
+
 		public PoolType getType() {
 			return type;
 		}
@@ -218,11 +224,20 @@ public class HttpClientProperties {
 			this.maxIdleTime = maxIdleTime;
 		}
 
+		public Duration getMaxLifeTime() {
+			return maxLifeTime;
+		}
+
+		public void setMaxLifeTime(Duration maxLifeTime) {
+			this.maxLifeTime = maxLifeTime;
+		}
+
 		@Override
 		public String toString() {
 			return "Pool{" + "type=" + type + ", name='" + name + '\''
 					+ ", maxConnections=" + maxConnections + ", acquireTimeout="
-					+ acquireTimeout + '}';
+					+ acquireTimeout + ", maxIdleTime=" + maxIdleTime + ", maxLifeTime="
+					+ maxLifeTime + '}';
 		}
 
 		public enum PoolType {