binder: Set default idle timeout to 60 seconds, and enable "strict lifecycle management".

binder/src/main/java/io/grpc/binder/BinderChannelBuilder.java

@@ -17,6 +17,7 @@
 package io.grpc.binder;
 
 import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.base.Preconditions.checkState;
 
 import android.app.Application;
 import android.content.ComponentName;
@@ -124,6 +125,7 @@ public static BinderChannelBuilder forTarget(String target) {
   private SecurityPolicy securityPolicy;
   private InboundParcelablePolicy inboundParcelablePolicy;
   private BindServiceFlags bindServiceFlags;
+  private boolean strictLifecycleManagement;
 
   private BinderChannelBuilder(
       @Nullable AndroidComponentAddress directAddress,
@@ -134,6 +136,7 @@ private BinderChannelBuilder(
     securityPolicy = SecurityPolicies.internalOnly();
     inboundParcelablePolicy = InboundParcelablePolicy.DEFAULT;
     bindServiceFlags = BindServiceFlags.DEFAULTS;
+    idleTimeout(60, TimeUnit.SECONDS);
 
     final class BinderChannelTransportFactoryBuilder
         implements ClientTransportFactoryBuilder {
@@ -224,6 +227,23 @@ public BinderChannelBuilder inboundParcelablePolicy(
     return this;
   }
 
+  /** 
+    * Enables strict lifecycle management. This should be called by processes with elevated procrank, where
+    * reliance on idle timers is inappropriate for lifecycle management.
+    */
+  public BinderChannelBuilder strictLifecycleManagement() {
+    strictLifecycleManagement = true;
+    super.idleTimeout(1000, TimeUnit.DAYS); // >30 days disables timeouts entirely.
+    return this;
+  }
+
+  @Override
+  public BinderChannelBuilder idleTimeout(long value, TimeUnit unit) {
+    checkState(!strictLifecycleManagement, "Idle timeouts are not supported when strict lifecycle management is enabled");
+    super.idleTimeout(value, unit);
+    return this;
+  }
+
   /** Creates new binder transports. */
   private static final class TransportFactory implements ClientTransportFactory {
     private final Context sourceContext;

binder/src/test/java/io/grpc/binder/BinderChannelBuilderTest.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2020 The gRPC 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 io.grpc.binder;
+
+import static org.junit.Assert.fail;
+
+import android.content.Context;
+import androidx.test.core.app.ApplicationProvider;
+import java.util.concurrent.TimeUnit;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+
+@RunWith(RobolectricTestRunner.class)
+public final class BinderChannelBuilderTest {
+  private final Context appContext = ApplicationProvider.getApplicationContext();
+  private final AndroidComponentAddress addr = AndroidComponentAddress.forContext(appContext);
+
+  @Test
+  public void strictLifecycleManagementForbidsIdleTimers() {
+    BinderChannelBuilder builder = BinderChannelBuilder.forAddress(addr, appContext);
+    builder.strictLifecycleManagement();
+    try {
+      builder.idleTimeout(10, TimeUnit.SECODNS);
+      fail();
+    } catch (IllegalStateException ise) {
+      // Expected.
+    }
+  }
+}