From dab8f973a577d9293e8c6620f0046aa90c1df9fa Mon Sep 17 00:00:00 2001
From: Spencer Gibb <spencer@gibb.us>
Date: Mon, 19 Mar 2018 12:17:08 -0400
Subject: [PATCH] Returns empty list when zookeeper throws NoNodeException.

This will allow apps that use DiscoveryClient to continue to function as services register.

This is a common occurrence in testing situations.

Fixes gh-164
---
 .../discovery/ZookeeperDiscoveryClient.java   | 16 ++++++++--
 .../ZookeeperDiscoveryClientTests.java        | 29 +++++++++++++++++++
 2 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/spring-cloud-zookeeper-discovery/src/main/java/org/springframework/cloud/zookeeper/discovery/ZookeeperDiscoveryClient.java b/spring-cloud-zookeeper-discovery/src/main/java/org/springframework/cloud/zookeeper/discovery/ZookeeperDiscoveryClient.java
index ee923c35..853321d7 100644
--- a/spring-cloud-zookeeper-discovery/src/main/java/org/springframework/cloud/zookeeper/discovery/ZookeeperDiscoveryClient.java
+++ b/spring-cloud-zookeeper-discovery/src/main/java/org/springframework/cloud/zookeeper/discovery/ZookeeperDiscoveryClient.java
@@ -25,9 +25,9 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.curator.x.discovery.ServiceDiscovery;
 import org.apache.curator.x.discovery.ServiceInstance;
+import org.apache.zookeeper.KeeperException;
 import org.springframework.cloud.client.discovery.DiscoveryClient;
 import org.springframework.cloud.zookeeper.discovery.dependency.ZookeeperDependencies;
-import org.springframework.util.ReflectionUtils;
 
 import static org.springframework.util.ReflectionUtils.rethrowRuntimeException;
 
@@ -91,8 +91,14 @@ public class ZookeeperDiscoveryClient implements DiscoveryClient {
 				instances.add(createServiceInstance(serviceIdToQuery, instance));
 			}
 			return instances;
+		} catch (KeeperException.NoNodeException e) {
+			if (log.isDebugEnabled()) {
+				log.debug("Error getting instances from zookeeper. Possibly, no service has registered.", e);
+			}
+			// this means that nothing has registered as a service yes
+			return Collections.emptyList();
 		} catch (Exception exception) {
-			ReflectionUtils.rethrowRuntimeException(exception);
+			rethrowRuntimeException(exception);
 		}
 		return new ArrayList<>();
 	}
@@ -124,6 +130,12 @@ public class ZookeeperDiscoveryClient implements DiscoveryClient {
 		}
 		try {
 			services = new ArrayList<>(getServiceDiscovery().queryForNames());
+		} catch (KeeperException.NoNodeException e) {
+			if (log.isDebugEnabled()) {
+				log.debug("Error getting instances from zookeeper. Possibly, no service has registered.", e);
+			}
+			// this means that nothing has registered as a service yes
+			return Collections.emptyList();
 		}
 		catch (Exception e) {
 			rethrowRuntimeException(e);
diff --git a/spring-cloud-zookeeper-discovery/src/test/java/org/springframework/cloud/zookeeper/discovery/ZookeeperDiscoveryClientTests.java b/spring-cloud-zookeeper-discovery/src/test/java/org/springframework/cloud/zookeeper/discovery/ZookeeperDiscoveryClientTests.java
index 0559f668..1b6b3523 100644
--- a/spring-cloud-zookeeper-discovery/src/test/java/org/springframework/cloud/zookeeper/discovery/ZookeeperDiscoveryClientTests.java
+++ b/spring-cloud-zookeeper-discovery/src/test/java/org/springframework/cloud/zookeeper/discovery/ZookeeperDiscoveryClientTests.java
@@ -2,10 +2,15 @@ package org.springframework.cloud.zookeeper.discovery;
 
 import java.util.List;
 
+import org.apache.curator.x.discovery.ServiceDiscovery;
+import org.apache.zookeeper.KeeperException.NoNodeException;
 import org.junit.Test;
 
+import org.springframework.cloud.client.ServiceInstance;
+
 import static org.assertj.core.api.BDDAssertions.then;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 /**
  * @author Marcin Grzejszczak
@@ -21,4 +26,28 @@ public class ZookeeperDiscoveryClientTests {
 		// then:
 		then(services).isEmpty();
 	}
+
+	@Test
+	public void getServicesShouldReturnEmptyWhenNoNodeException() throws Exception {
+		// given:
+		ServiceDiscovery<ZookeeperInstance> serviceDiscovery = mock(ServiceDiscovery.class);
+		when(serviceDiscovery.queryForNames()).thenThrow(new NoNodeException());
+		ZookeeperDiscoveryClient discoveryClient = new ZookeeperDiscoveryClient(serviceDiscovery, null);
+		// when:
+		List<String> services = discoveryClient.getServices();
+		// then:
+		then(services).isEmpty();
+	}
+
+	@Test
+	public void getInstancesshouldReturnEmptyWhenNoNodeException() throws Exception {
+		// given:
+		ServiceDiscovery<ZookeeperInstance> serviceDiscovery = mock(ServiceDiscovery.class);
+		when(serviceDiscovery.queryForInstances("myservice")).thenThrow(new NoNodeException());
+		ZookeeperDiscoveryClient discoveryClient = new ZookeeperDiscoveryClient(serviceDiscovery, null);
+		// when:
+		List<ServiceInstance> instances = discoveryClient.getInstances("myservice");
+		// then:
+		then(instances).isEmpty();
+	}
 }