Add basic component initialization tracing (#3986)

* Add basic component initialization tracing

* Review changes

* Add unit test and review changes

* Add missing copyright header

* Formatting

Author: emilypgoogle

firebase-common/src/main/java/com/google/firebase/FirebaseApp.java

@@ -51,6 +51,8 @@
 import com.google.firebase.heartbeatinfo.DefaultHeartBeatController;
 import com.google.firebase.inject.Provider;
 import com.google.firebase.internal.DataCollectionConfigStorage;
+import com.google.firebase.tracing.ComponentMonitor;
+import com.google.firebase.tracing.FirebaseTrace;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -415,18 +417,25 @@ protected FirebaseApp(Context applicationContext, String name, FirebaseOptions o
     this.name = Preconditions.checkNotEmpty(name);
     this.options = Preconditions.checkNotNull(options);
 
+    FirebaseTrace.pushTrace("Firebase");
+
+    FirebaseTrace.pushTrace("ComponentDiscovery");
     List<Provider<ComponentRegistrar>> registrars =
         ComponentDiscovery.forContext(applicationContext, ComponentDiscoveryService.class)
             .discoverLazy();
+    FirebaseTrace.popTrace(); // ComponentDiscovery
 
+    FirebaseTrace.pushTrace("Runtime");
     componentRuntime =
         ComponentRuntime.builder(UI_EXECUTOR)
             .addLazyComponentRegistrars(registrars)
             .addComponentRegistrar(new FirebaseCommonRegistrar())
             .addComponent(Component.of(applicationContext, Context.class))
             .addComponent(Component.of(this, FirebaseApp.class))
             .addComponent(Component.of(options, FirebaseOptions.class))
+            .setProcessor(new ComponentMonitor())
             .build();
+    FirebaseTrace.popTrace(); // Runtime
 
     dataCollectionConfigStorage =
         new Lazy<>(
@@ -443,6 +452,8 @@ protected FirebaseApp(Context applicationContext, String name, FirebaseOptions o
             defaultHeartBeatController.get().registerHeartBeat();
           }
         });
+
+    FirebaseTrace.popTrace(); // Firebase
   }
 
   private void checkNotDeleted() {

firebase-common/src/main/java/com/google/firebase/tracing/ComponentMonitor.java

@@ -0,0 +1,48 @@
+// Copyright 2022 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.firebase.tracing;
+
+import com.google.firebase.components.Component;
+import com.google.firebase.components.ComponentRegistrar;
+import com.google.firebase.components.ComponentRegistrarProcessor;
+import java.util.ArrayList;
+import java.util.List;
+
+/** Wraps components to trace their initialization time. */
+public class ComponentMonitor implements ComponentRegistrarProcessor {
+  @Override
+  public List<Component<?>> processRegistrar(ComponentRegistrar registrar) {
+    List<Component<?>> components = new ArrayList<>();
+    for (Component comp : registrar.getComponents()) {
+      String name = comp.getName();
+      if (name != null) {
+        @SuppressWarnings("unchecked")
+        Component<Object> old = (Component<Object>) comp;
+        comp =
+            old.withFactory(
+                c -> {
+                  try {
+                    FirebaseTrace.pushTrace(name);
+                    return old.getFactory().create(c);
+                  } finally {
+                    FirebaseTrace.popTrace();
+                  }
+                });
+      }
+      components.add(comp);
+    }
+    return components;
+  }
+}

firebase-common/src/main/java/com/google/firebase/tracing/FirebaseTrace.java

@@ -0,0 +1,36 @@
+// Copyright 2022 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.firebase.tracing;
+
+import android.os.Build;
+import android.os.Trace;
+
+/** Utility to consistently wrap trace calls with version checking. */
+public final class FirebaseTrace {
+
+  private FirebaseTrace() {}
+
+  public static void pushTrace(String name) {
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
+      Trace.beginSection(name);
+    }
+  }
+
+  public static void popTrace() {
+    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
+      Trace.endSection();
+    }
+  }
+}

firebase-common/src/main/java/com/google/firebase/tracing/package-info.java

@@ -0,0 +1,16 @@
+// Copyright 2022 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.
+
+/** @hide */
+package com.google.firebase.tracing;

firebase-common/src/test/java/com/google/firebase/tracing/ComponentMonitorTest.java

@@ -0,0 +1,58 @@
+// Copyright 2022 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.firebase.tracing;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import com.google.firebase.components.Component;
+import com.google.firebase.components.ComponentContainer;
+import java.util.ArrayList;
+import java.util.List;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@RunWith(AndroidJUnit4.class)
+public class ComponentMonitorTest {
+
+  @Test
+  public void testComponentMonitorTransformation() {
+    List<Component<?>> list = new ArrayList<Component<?>>();
+    list.add(
+        Component.builder(ComponentHolder.class)
+            .factory(ComponentHolder::new)
+            .name("test")
+            .build());
+    list.add(
+        Component.builder(ComponentHolder.class).factory(ComponentHolder::new).name("foo").build());
+    list.add(
+        Component.builder(ComponentHolder.class).factory(ComponentHolder::new).name("bar").build());
+    ComponentMonitor monitor = new ComponentMonitor();
+    List<Component<?>> transformed = monitor.processRegistrar(() -> list);
+    assertThat(list.size()).isEqualTo(transformed.size());
+    for (int i = 0; i < list.size(); i++) {
+      assertThat(list.get(i).getName()).isEqualTo(transformed.get(i).getName());
+      assertThat(transformed.get(i).getFactory().create(null)).isNotNull();
+    }
+  }
+
+  private static final class ComponentHolder {
+    private final ComponentContainer container;
+
+    public ComponentHolder(ComponentContainer container) {
+      this.container = container;
+    }
+  }
+}