Minor improvements to error messages for netflix.atlas.uri problems

spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/metrics/atlas/AtlasMetricObserver.java

@@ -95,9 +95,14 @@ public class AtlasMetricObserver implements MetricObserver {
 	}
 
 	protected static String normalizeAtlasUri(String uri) {
-		Matcher matcher = Pattern.compile("(.+?)(/api/v1/publish)?/?").matcher(uri);
-		matcher.matches();
-		return matcher.group(1) + "/api/v1/publish";
+		if (uri != null) {
+			Matcher matcher = Pattern.compile("(.+?)(/api/v1/publish)?/?").matcher(uri);
+			if (matcher.matches())
+				return matcher.group(1) + "/api/v1/publish";
+			else
+				throw new IllegalStateException("netflix.atlas.uri is not a valid uri");
+		}
+		throw new IllegalStateException("netflix.atlas.uri was not found in your properties and is required to communicate with Atlas");
 	}
 
 	@Override

spring-cloud-netflix-core/src/test/java/org/springframework/cloud/netflix/metrics/atlas/AtlasMetricObserverTests.java

@@ -53,6 +53,16 @@ public class AtlasMetricObserverTests {
 		assertEquals(normalized, AtlasMetricObserver.normalizeAtlasUri("http://localhost:7001/api/v1/publish/"));
 	}
 
+	@Test(expected = IllegalStateException.class)
+	public void emptyAtlasUriThrowsException() {
+		AtlasMetricObserver.normalizeAtlasUri("");
+	}
+
+	@Test(expected = IllegalStateException.class)
+	public void missingAtlasUriThrowsException() {
+		AtlasMetricObserver.normalizeAtlasUri(null);
+	}
+
 	@Test
 	public void checkValidityOfTags() {
 		assertTrue(AtlasMetricObserver.validTags(BasicTagList.of("foo", "bar")));