Apply ip resolver logic to pool also

Author: tomas-sexenian

java/src/main/java/com/genexus/internet/HttpClientJavaLib.java

@@ -18,10 +18,12 @@
 import org.apache.http.*;
 import org.apache.http.HttpResponse;
 import org.apache.http.client.config.CookieSpecs;
+import org.apache.http.conn.DnsResolver;
 import org.apache.http.conn.routing.HttpRoute;
 import org.apache.http.conn.ssl.NoopHostnameVerifier;
 import org.apache.http.entity.ContentType;
 import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
+import org.apache.http.impl.conn.SystemDefaultDnsResolver;
 import org.apache.http.protocol.HttpContext;
 import org.apache.http.auth.AuthSchemeProvider;
 import org.apache.http.auth.AuthScope;
@@ -64,10 +66,44 @@
 
 public class HttpClientJavaLib extends GXHttpClient {
 
+	private static class FirstIpDnsResolver implements DnsResolver {
+		private final DnsResolver defaultDnsResolver = new SystemDefaultDnsResolver();
+
+		@Override
+		public InetAddress[] resolve(final String host) throws UnknownHostException {
+			InetAddress[] allIps = defaultDnsResolver.resolve(host);
+			if (allIps != null && allIps.length > 0) {
+				return new InetAddress[]{allIps[0]};
+			}
+			return allIps;
+		}
+	}
+
+	private static String getGxIpResolverConfig() {
+		String name = "GX_USE_FIRST_IP_DNS";
+		String gxDns = System.getProperty(name);
+		if (gxDns == null || gxDns.trim().isEmpty()) {
+			gxDns = System.getenv(name);
+		}
+		if (gxDns != null && gxDns.trim().equalsIgnoreCase("true")) {
+			return gxDns.trim();
+		} else {
+			return null;
+		}
+	}
+
+
 	public HttpClientJavaLib() {
 		getPoolInstance();
 		ConnectionKeepAliveStrategy myStrategy = generateKeepAliveStrategy();
-		httpClientBuilder = HttpClients.custom().setConnectionManager(connManager).setConnectionManagerShared(true).setKeepAliveStrategy(myStrategy);
+		HttpClientBuilder builder = HttpClients.custom()
+			.setConnectionManager(connManager)
+			.setConnectionManagerShared(true)
+			.setKeepAliveStrategy(myStrategy);
+		if (getGxIpResolverConfig() != null) {
+			builder.setDnsResolver(new FirstIpDnsResolver());
+		}
+		httpClientBuilder = builder;
 		cookies = new BasicCookieStore();		
 		streamsToClose = new Vector<>();
 	}
@@ -78,7 +114,13 @@ private static void getPoolInstance() {
 				RegistryBuilder.<ConnectionSocketFactory>create()
 					.register("http", PlainConnectionSocketFactory.INSTANCE).register("https", getSSLSecureInstance())
 					.build();
-			connManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);
+			String useFirstIpDnsResolver = getGxIpResolverConfig();
+			if (useFirstIpDnsResolver != null) {
+				DnsResolver dnsResolver = new FirstIpDnsResolver();
+				connManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry, dnsResolver);
+			} else {
+				connManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);
+			}
 			connManager.setMaxTotal((int) CommonUtil.val(clientCfg.getProperty("Client", "HTTPCLIENT_MAX_SIZE", "1000")));
 			connManager.setDefaultMaxPerRoute((int) CommonUtil.val(clientCfg.getProperty("Client", "HTTPCLIENT_MAX_PER_ROUTE", "1000")));