From 9dc93c5c9372f1501006e2d3a3a7affecd65fb8e Mon Sep 17 00:00:00 2001
From: Igor Bernstein <igorbernstein@google.com>
Date: Wed, 5 Jan 2022 09:49:19 -0500
Subject: [PATCH] fix: align ip version preference for the wrapped  emulator
 (#1052)

* fix: align ip version preference for the wrapped  emulator

When the  emulator wrapper is started with -Djava.net.preferIPv6Addresses=true on a machine that defaults to ipv4,
the golang emulator and the java client will pick different ip stacks and not be able to connect. This change will
use java to resolve the localhost's ip address and push it down to the golang emulator

* remove debug

* whitespace
---
 .../cloud/bigtable/emulator/v2/Emulator.java  | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/google-cloud-bigtable-emulator/src/main/java/com/google/cloud/bigtable/emulator/v2/Emulator.java b/google-cloud-bigtable-emulator/src/main/java/com/google/cloud/bigtable/emulator/v2/Emulator.java
index 4ddc3620e..b43322831 100644
--- a/google-cloud-bigtable-emulator/src/main/java/com/google/cloud/bigtable/emulator/v2/Emulator.java
+++ b/google-cloud-bigtable-emulator/src/main/java/com/google/cloud/bigtable/emulator/v2/Emulator.java
@@ -25,10 +25,13 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.net.InetAddress;
 import java.net.ServerSocket;
 import java.net.Socket;
+import java.net.UnknownHostException;
 import java.nio.file.Path;
 import java.util.Locale;
+import java.util.Optional;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.logging.Level;
@@ -98,10 +101,24 @@ public synchronized void start() throws IOException, TimeoutException, Interrupt
     }
     this.port = getAvailablePort();
 
+    // Try to align the localhost address across java & golang emulator
+    // This should fix issues on systems that default to ipv4 but the jvm is started with
+    // -Djava.net.preferIPv6Addresses=true
+    Optional<String> localhostAddress = Optional.empty();
+    try {
+      localhostAddress = Optional.of(InetAddress.getByName(null).getHostAddress());
+    } catch (UnknownHostException e) {
+    }
+
     // Workaround https://bugs.openjdk.java.net/browse/JDK-8068370
     for (int attemptsLeft = 3; process == null; attemptsLeft--) {
       try {
-        process = Runtime.getRuntime().exec(String.format("%s -port %d", executable, port));
+        String cmd = executable.toString();
+        if (localhostAddress.isPresent()) {
+          cmd += String.format(" -host [%s]", localhostAddress.get());
+        }
+        cmd += String.format(" -port %d", port);
+        process = Runtime.getRuntime().exec(cmd);
       } catch (IOException e) {
         if (attemptsLeft > 0) {
           Thread.sleep(1000);