From fdc0a97553d3aecfa834e0c78f9dd1b94e3ff795 Mon Sep 17 00:00:00 2001
From: David Liu <dliu@netflix.com>
Date: Mon, 4 Jan 2016 18:19:36 -0800
Subject: [PATCH 1/2] add additional sanity check in shouldRefresh AmazonInfo

---
 .../netflix/appinfo/CloudInstanceConfig.java    | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/eureka-client/src/main/java/com/netflix/appinfo/CloudInstanceConfig.java b/eureka-client/src/main/java/com/netflix/appinfo/CloudInstanceConfig.java
index 82394b9518..840abc3259 100644
--- a/eureka-client/src/main/java/com/netflix/appinfo/CloudInstanceConfig.java
+++ b/eureka-client/src/main/java/com/netflix/appinfo/CloudInstanceConfig.java
@@ -163,7 +163,7 @@ public String[] getDefaultAddressResolutionOrder() {
     public synchronized void refreshAmazonInfo() {
         try {
             AmazonInfo newInfo = AmazonInfo.Builder.newBuilder().autoBuild(namespace);
-            if (!newInfo.equals(info)) {
+            if (shouldUpdate(newInfo, info)) {
                 // the datacenter info has changed, re-sync it
                 logger.warn("The AmazonInfo changed from : {} => {}", info, newInfo);
                 this.info = newInfo;
@@ -172,4 +172,19 @@ public synchronized void refreshAmazonInfo() {
             logger.error("Cannot refresh the Amazon Info ", t);
         }
     }
+
+    private static boolean shouldUpdate(AmazonInfo newInfo, AmazonInfo oldInfo) {
+        if (newInfo.getMetadata().isEmpty()) {
+            logger.warn("Newly resolved AmazonInfo is empty, skipping an update cycle");
+            return false;
+        } else if (!newInfo.equals(oldInfo)) {
+            int newKeySize = newInfo.getMetadata().size();
+            int oldKeySize = oldInfo.getMetadata().size();
+            if (newKeySize < oldKeySize) {
+                logger.warn("Newly resolved AmazonInfo contains less data than previous old:{} -> new:{}, skipping an update cycle", oldKeySize, newKeySize);
+                return false;
+            }
+        }
+        return true;
+    }
 }

From 675e0843acb5ffaa55726f8caf1ed7c04f5ffde9 Mon Sep 17 00:00:00 2001
From: David Liu <dliu@netflix.com>
Date: Mon, 4 Jan 2016 19:25:57 -0800
Subject: [PATCH 2/2] logic fix + adding test case

---
 .../netflix/appinfo/CloudInstanceConfig.java  |  8 ++---
 .../appinfo/CloudInstanceConfigTest.java      | 35 +++++++++++++++++++
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/eureka-client/src/main/java/com/netflix/appinfo/CloudInstanceConfig.java b/eureka-client/src/main/java/com/netflix/appinfo/CloudInstanceConfig.java
index 840abc3259..973fc20c62 100644
--- a/eureka-client/src/main/java/com/netflix/appinfo/CloudInstanceConfig.java
+++ b/eureka-client/src/main/java/com/netflix/appinfo/CloudInstanceConfig.java
@@ -173,18 +173,18 @@ public synchronized void refreshAmazonInfo() {
         }
     }
 
-    private static boolean shouldUpdate(AmazonInfo newInfo, AmazonInfo oldInfo) {
+    /* visible for testing */ static boolean shouldUpdate(AmazonInfo newInfo, AmazonInfo oldInfo) {
         if (newInfo.getMetadata().isEmpty()) {
             logger.warn("Newly resolved AmazonInfo is empty, skipping an update cycle");
-            return false;
         } else if (!newInfo.equals(oldInfo)) {
             int newKeySize = newInfo.getMetadata().size();
             int oldKeySize = oldInfo.getMetadata().size();
             if (newKeySize < oldKeySize) {
                 logger.warn("Newly resolved AmazonInfo contains less data than previous old:{} -> new:{}, skipping an update cycle", oldKeySize, newKeySize);
-                return false;
+            } else {  // final case that warrants an update
+                return true;
             }
         }
-        return true;
+        return false;
     }
 }
diff --git a/eureka-client/src/test/java/com/netflix/appinfo/CloudInstanceConfigTest.java b/eureka-client/src/test/java/com/netflix/appinfo/CloudInstanceConfigTest.java
index 344587e388..ab355fab4b 100644
--- a/eureka-client/src/test/java/com/netflix/appinfo/CloudInstanceConfigTest.java
+++ b/eureka-client/src/test/java/com/netflix/appinfo/CloudInstanceConfigTest.java
@@ -67,4 +67,39 @@ public void testResolveDefaultAddress() {
         config.info.getMetadata().remove(localIpv4.getName());
         assertThat(config.resolveDefaultAddress(), is(dummyDefault));
     }
+
+    @Test
+    public void testAmazonInfoUpdate() {
+        AmazonInfo oldInfo = (AmazonInfo) instanceInfo.getDataCenterInfo();
+
+        // false for update if equal
+        AmazonInfo newInfo1 = oldInfo;
+        assertThat(CloudInstanceConfig.shouldUpdate(newInfo1, oldInfo), is(false));
+
+        // false for update if new is empty
+        AmazonInfo newInfo2 = new AmazonInfo();
+        assertThat(CloudInstanceConfig.shouldUpdate(newInfo2, oldInfo), is(false));
+
+        AmazonInfo newInfo3 = new AmazonInfo();
+        for (String key : oldInfo.getMetadata().keySet()) {
+            newInfo3.getMetadata().put(key, oldInfo.getMetadata().get(key));
+        }
+        int originalInfo3Size = newInfo3.getMetadata().size();
+
+        // true for update if new contains diff data
+        newInfo3.getMetadata().put(AmazonInfo.MetaDataKey.instanceId.getName(), "foo");
+        assertThat(CloudInstanceConfig.shouldUpdate(newInfo3, oldInfo), is(true));
+
+        // true for update if new contains more data
+        String newKey = "someNewKey";
+        newInfo3.getMetadata().put(newKey, "bar");
+        assertThat(newInfo3.getMetadata().size(), is(originalInfo3Size + 1));
+        assertThat(CloudInstanceConfig.shouldUpdate(newInfo3, oldInfo), is(true));
+
+        // false if there is now less data
+        newInfo3.getMetadata().remove(newKey);
+        newInfo3.getMetadata().remove(AmazonInfo.MetaDataKey.instanceId.getName());
+        assertThat(newInfo3.getMetadata().size(), is(originalInfo3Size - 1));
+        assertThat(CloudInstanceConfig.shouldUpdate(newInfo3, oldInfo), is(false));
+    }
 }