Future-proof TransportBackend. (#318)

The PR changes the signature of `send()` to take `BackendRequest` as
parameter. This allows us to evolve the API in a backwards compatible
way in the furure.

Author: vkryachko

transport/transport-backend-cct/src/main/java/com/google/android/datatransport/cct/GoogleTransportBackend.java

@@ -23,6 +23,7 @@
 import com.google.android.datatransport.cct.proto.LogRequest;
 import com.google.android.datatransport.cct.proto.LogResponse;
 import com.google.android.datatransport.cct.proto.QosTierConfiguration;
+import com.google.android.datatransport.runtime.BackendRequest;
 import com.google.android.datatransport.runtime.BackendResponse;
 import com.google.android.datatransport.runtime.BackendResponse.Status;
 import com.google.android.datatransport.runtime.EventInternal;
@@ -105,9 +106,9 @@ public EventInternal decorate(EventInternal eventInternal) {
         .build();
   }
 
-  private BatchedLogRequest getRequestBody(Iterable<EventInternal> eventInternals) {
+  private BatchedLogRequest getRequestBody(BackendRequest backendRequest) {
     HashMap<String, List<EventInternal>> eventInternalMap = new HashMap<>();
-    for (EventInternal eventInternal : eventInternals) {
+    for (EventInternal eventInternal : backendRequest.getEvents()) {
       String key = eventInternal.getTransportName();
       if (!eventInternalMap.containsKey(key)) {
         List<EventInternal> eventInternalList = new ArrayList<EventInternal>();
@@ -192,8 +193,8 @@ private BackendResponse doSend(BatchedLogRequest requestBody) throws IOException
   }
 
   @Override
-  public BackendResponse send(Iterable<EventInternal> events) {
-    BatchedLogRequest requestBody = getRequestBody(events);
+  public BackendResponse send(BackendRequest request) {
+    BatchedLogRequest requestBody = getRequestBody(request);
     try {
       return doSend(requestBody);
     } catch (IOException e) {

transport/transport-backend-cct/src/test/java/com/google/android/datatransport/cct/GoogleTransportBackendTest.java

@@ -26,6 +26,7 @@
 import com.github.tomakehurst.wiremock.junit.WireMockRule;
 import com.google.android.datatransport.Priority;
 import com.google.android.datatransport.cct.proto.LogResponse;
+import com.google.android.datatransport.runtime.BackendRequest;
 import com.google.android.datatransport.runtime.BackendResponse;
 import com.google.android.datatransport.runtime.BackendResponse.Status;
 import com.google.android.datatransport.runtime.EventInternal;
@@ -45,16 +46,17 @@ public class GoogleTransportBackendTest {
 
   @Rule public WireMockRule wireMockRule = new WireMockRule(8999);
 
-  private Iterable<EventInternal> getEventInternalIterable() {
-    return Collections.singleton(
-        BACKEND.decorate(
-            EventInternal.builder()
-                .setEventMillis(3)
-                .setUptimeMillis(1)
-                .setTransportName(TRANSPORT_NAME)
-                .setPriority(Priority.DEFAULT)
-                .setPayload("TelemetryData".getBytes())
-                .build()));
+  private BackendRequest getBackendRequest() {
+    return BackendRequest.create(
+        Collections.singleton(
+            BACKEND.decorate(
+                EventInternal.builder()
+                    .setEventMillis(3)
+                    .setUptimeMillis(1)
+                    .setTransportName(TRANSPORT_NAME)
+                    .setPriority(Priority.DEFAULT)
+                    .setPayload("TelemetryData".getBytes())
+                    .build())));
   }
 
   @Test
@@ -70,7 +72,7 @@ public void testSuccessLoggingRequest() {
                             .setNextRequestWaitMillis(3)
                             .build()
                             .toByteArray())));
-    BackendResponse response = BACKEND.send(getEventInternalIterable());
+    BackendResponse response = BACKEND.send(getBackendRequest());
     verify(
         postRequestedFor(urlEqualTo("/api"))
             .withHeader("Content-Type", equalTo("application/x-protobuf")));
@@ -81,7 +83,7 @@ public void testSuccessLoggingRequest() {
   @Test
   public void testUnsuccessfulLoggingRequest() {
     stubFor(post(urlEqualTo("/api")).willReturn(aResponse().withStatus(404)));
-    BackendResponse response = BACKEND.send(getEventInternalIterable());
+    BackendResponse response = BACKEND.send(getBackendRequest());
     verify(
         postRequestedFor(urlEqualTo("/api"))
             .withHeader("Content-Type", equalTo("application/x-protobuf")));
@@ -92,7 +94,7 @@ public void testUnsuccessfulLoggingRequest() {
   @Test
   public void testServerErrorLoggingRequest() {
     stubFor(post(urlEqualTo("/api")).willReturn(aResponse().withStatus(500)));
-    BackendResponse response = BACKEND.send(getEventInternalIterable());
+    BackendResponse response = BACKEND.send(getBackendRequest());
     verify(
         postRequestedFor(urlEqualTo("/api"))
             .withHeader("Content-Type", equalTo("application/x-protobuf")));
@@ -109,7 +111,7 @@ public void testGarbageFromServer() {
                     .withStatus(200)
                     .withHeader("Content-Type", "application/x-protobuf;charset=UTF8;hello=world")
                     .withBody("{\"status\":\"Error\",\"message\":\"Endpoint not found\"}")));
-    BackendResponse response = BACKEND.send(getEventInternalIterable());
+    BackendResponse response = BACKEND.send(getBackendRequest());
     verify(
         postRequestedFor(urlEqualTo("/api"))
             .withHeader("Content-Type", equalTo("application/x-protobuf")));
@@ -120,7 +122,7 @@ public void testGarbageFromServer() {
   @Test
   public void testNonHandledResponseCode() {
     stubFor(post(urlEqualTo("/api")).willReturn(aResponse().withStatus(300)));
-    BackendResponse response = BACKEND.send(getEventInternalIterable());
+    BackendResponse response = BACKEND.send(getBackendRequest());
     verify(
         postRequestedFor(urlEqualTo("/api"))
             .withHeader("Content-Type", equalTo("application/x-protobuf")));

transport/transport-runtime/src/main/java/com/google/android/datatransport/runtime/BackendRequest.java

@@ -0,0 +1,29 @@
+// Copyright 2018 Google LLC
+//
+// 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 com.google.android.datatransport.runtime;
+
+import com.google.auto.value.AutoValue;
+
+/** Encapsulates a send request made to an individual {@link TransportBackend}. */
+@AutoValue
+public abstract class BackendRequest {
+  /** Events to be sent to the backend. */
+  public abstract Iterable<EventInternal> getEvents();
+
+  /** Creates a new instance of the request. */
+  public static BackendRequest create(Iterable<EventInternal> events) {
+    return new AutoValue_BackendRequest(events);
+  }
+}

transport/transport-runtime/src/main/java/com/google/android/datatransport/runtime/TransportBackend.java

@@ -17,5 +17,5 @@
 public interface TransportBackend {
   EventInternal decorate(EventInternal event);
 
-  BackendResponse send(Iterable<EventInternal> event);
+  BackendResponse send(BackendRequest backendRequest);
 }

transport/transport-runtime/src/main/java/com/google/android/datatransport/runtime/TransportFactoryImpl.java

@@ -18,8 +18,8 @@
 import com.google.android.datatransport.Transport;
 import com.google.android.datatransport.TransportFactory;
 
-public final class TransportFactoryImpl implements TransportFactory {
-  private String backendName;
+final class TransportFactoryImpl implements TransportFactory {
+  private final String backendName;
   private final TransportInternal transportInternal;
 
   TransportFactoryImpl(String backendName, TransportInternal transportInternal) {

transport/transport-runtime/src/main/java/com/google/android/datatransport/runtime/TransportImpl.java

@@ -19,9 +19,9 @@
 import com.google.android.datatransport.Transport;
 
 class TransportImpl<T> implements Transport<T> {
-  private String backendName;
-  private String name;
-  private Transformer<T, byte[]> transformer;
+  private final String backendName;
+  private final String name;
+  private final Transformer<T, byte[]> transformer;
   private final TransportInternal transportInternal;
 
   TransportImpl(

transport/transport-runtime/src/main/java/com/google/android/datatransport/runtime/scheduling/ImmediateScheduler.java

@@ -15,6 +15,7 @@
 package com.google.android.datatransport.runtime.scheduling;
 
 import com.google.android.datatransport.runtime.BackendRegistry;
+import com.google.android.datatransport.runtime.BackendRequest;
 import com.google.android.datatransport.runtime.EventInternal;
 import com.google.android.datatransport.runtime.TransportBackend;
 import com.google.android.datatransport.runtime.TransportRuntime;
@@ -49,7 +50,7 @@ public void schedule(String backendName, EventInternal event) {
             LOGGER.warning(String.format("Transport backend '%s' is not registered", backendName));
             return;
           }
-          backend.send(Collections.singleton(backend.decorate(event)));
+          backend.send(BackendRequest.create(Collections.singleton(backend.decorate(event))));
         });
   }
 }

transport/transport-runtime/src/test/java/com/google/android/datatransport/runtime/TransportRuntimeTest.java

@@ -109,7 +109,8 @@ public <T> T runCriticalSection(
     verify(mockBackend, times(1))
         .send(
             eq(
-                Collections.singleton(
-                    expectedEvent.toBuilder().addMetadata(TEST_KEY, TEST_VALUE).build())));
+                BackendRequest.create(
+                    Collections.singleton(
+                        expectedEvent.toBuilder().addMetadata(TEST_KEY, TEST_VALUE).build()))));
   }
 }