Makes AWS Elasticsearch errors a bit more descriptive

See openzipkin-attic/docker-zipkin#161

zipkin-autoconfigure/storage-elasticsearch-aws/src/main/java/zipkin/autoconfigure/storage/elasticsearch/aws/ElasticsearchDomainEndpoint.java

@@ -22,9 +22,9 @@
 import okhttp3.OkHttpClient;
 import okhttp3.Request;
 import okhttp3.Response;
+import okio.Buffer;
 import zipkin.storage.elasticsearch.http.ElasticsearchHttpStorage;
 
-import static zipkin.internal.Util.checkArgument;
 import static zipkin.internal.Util.checkNotNull;
 import static zipkin2.elasticsearch.internal.JsonReaders.enterPath;
 
@@ -37,19 +37,29 @@ final class ElasticsearchDomainEndpoint implements ElasticsearchHttpStorage.Host
   ElasticsearchDomainEndpoint(OkHttpClient client, HttpUrl baseUrl, String domain) {
     this.client = checkNotNull(client, "client");
     this.describeElasticsearchDomain = new Request.Builder().url(checkNotNull(baseUrl, "baseUrl")
-        .newBuilder("2015-01-01/es/domain")
-        .addPathSegment(checkNotNull(domain, "domain")).build()).build();
+      .newBuilder("2015-01-01/es/domain")
+      .addPathSegment(checkNotNull(domain, "domain")).build()).build();
   }
 
   @Override public List<String> get() {
     try (Response response = client.newCall(describeElasticsearchDomain).execute()) {
+      String body = response.body().string();
       if (!response.isSuccessful()) {
-        throw new IllegalStateException(response.body().string());
+        String message = describeElasticsearchDomain.url().encodedPath()
+          + " failed with status " + response.code();
+        if (!body.isEmpty()) message += ": " + body;
+        throw new IllegalStateException(message);
       }
 
       JsonReader endpointReader =
-          enterPath(JsonReader.of(response.body().source()), "DomainStatus", "Endpoint");
-      checkArgument(endpointReader != null, "DomainStatus.Endpoint wasn't present in response");
+        enterPath(JsonReader.of(new Buffer().writeUtf8(body)), "DomainStatus", "Endpoint");
+
+      if (endpointReader == null) {
+        throw new IllegalStateException(
+          "DomainStatus.Endpoint wasn't present in response: " + body);
+      }
+
+      // TODO: DomainStatus.Endpoints which could also be present
 
       String endpoint = endpointReader.nextString();
       if (!endpoint.startsWith("https://")) {

zipkin-autoconfigure/storage-elasticsearch-aws/src/test/java/zipkin/autoconfigure/storage/elasticsearch/aws/ElasticsearchDomainEndpointTest.java

@@ -0,0 +1,69 @@
+/**
+ * Copyright 2015-2017 The OpenZipkin Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package zipkin.autoconfigure.storage.elasticsearch.aws;
+
+import okhttp3.OkHttpClient;
+import okhttp3.mockwebserver.MockResponse;
+import okhttp3.mockwebserver.MockWebServer;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ElasticsearchDomainEndpointTest {
+  @Rule public ExpectedException thrown = ExpectedException.none();
+  @Rule public MockWebServer es = new MockWebServer();
+
+  ElasticsearchDomainEndpoint client = new ElasticsearchDomainEndpoint(
+    new OkHttpClient(),
+    es.url(""),
+    "zipkin53"
+  );
+
+  @Test public void publicUrl() throws Exception {
+    es.enqueue(new MockResponse().setBody("{\n"
+      + "  \"DomainStatus\": {\n"
+      + "    \"Endpoint\": \"search-zipkin53-mhdyquzbwwzwvln6phfzr3lldi.ap-southeast-1.es.amazonaws.com\",\n"
+      + "    \"Endpoints\": null\n"
+      + "  }\n"
+      + "}"));
+
+    assertThat(client.get())
+      .containsExactly(
+        "https://search-zipkin53-mhdyquzbwwzwvln6phfzr3lldi.ap-southeast-1.es.amazonaws.com");
+  }
+
+  /** Not quite sure why, but some have reported receiving no URLs at all */
+  @Test public void noUrl() throws Exception {
+    // simplified.. URL is usually the only thing actually missing
+    String body = "{\"DomainStatus\": {}}";
+    es.enqueue(new MockResponse().setBody(body));
+
+    thrown.expect(IllegalStateException.class);
+    thrown.expectMessage("DomainStatus.Endpoint wasn't present in response: " + body);
+
+    client.get();
+  }
+
+  /** Not quite sure why, but some have reported receiving no URLs at all */
+  @Test public void unauthorizedNoMessage() throws Exception {
+    es.enqueue(new MockResponse().setResponseCode(403));
+
+    thrown.expect(IllegalStateException.class);
+    thrown.expectMessage("/2015-01-01/es/domain/zipkin53 failed with status 403");
+
+    client.get();
+  }
+}