Make a best effort attempt to flush reports at crash time

firebase-crashlytics/src/main/java/com/google/firebase/crashlytics/internal/common/Utils.java

@@ -134,6 +134,29 @@ public static <T> T awaitEvenIfOnMainThread(Task<T> task)
     }
   }
 
+  /** Invokes latch.await(timeout, unit) uninterruptibly. */
+  public static boolean awaitUninterruptibly(CountDownLatch latch, long timeout, TimeUnit unit) {
+    boolean interrupted = false;
+    try {
+      long remainingNanos = unit.toNanos(timeout);
+      long end = System.nanoTime() + remainingNanos;
+
+      while (true) {
+        try {
+          // CountDownLatch treats negative timeouts just like zero.
+          return latch.await(remainingNanos, TimeUnit.NANOSECONDS);
+        } catch (InterruptedException e) {
+          interrupted = true;
+          remainingNanos = end - System.nanoTime();
+        }
+      }
+    } finally {
+      if (interrupted) {
+        Thread.currentThread().interrupt();
+      }
+    }
+  }
+
   /**
    * ExecutorService that is used exclusively by the awaitEvenIfOnMainThread function. If the
    * Continuation which counts down the latch is called on the same thread which is waiting on the

firebase-crashlytics/src/main/java/com/google/firebase/crashlytics/internal/send/ReportQueue.java

@@ -14,17 +14,22 @@
 
 package com.google.firebase.crashlytics.internal.send;
 
+import android.annotation.SuppressLint;
 import com.google.android.datatransport.Event;
+import com.google.android.datatransport.Priority;
 import com.google.android.datatransport.Transport;
+import com.google.android.datatransport.runtime.ForcedSender;
 import com.google.android.gms.tasks.TaskCompletionSource;
 import com.google.firebase.crashlytics.internal.Logger;
 import com.google.firebase.crashlytics.internal.common.CrashlyticsReportWithSessionId;
 import com.google.firebase.crashlytics.internal.common.OnDemandCounter;
+import com.google.firebase.crashlytics.internal.common.Utils;
 import com.google.firebase.crashlytics.internal.model.CrashlyticsReport;
 import com.google.firebase.crashlytics.internal.settings.Settings;
 import java.util.Locale;
 import java.util.concurrent.ArrayBlockingQueue;
 import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 
@@ -115,6 +120,18 @@ TaskCompletionSource<CrashlyticsReportWithSessionId> enqueueReport(
     }
   }
 
+  @SuppressLint("DiscouragedApi") // best effort only
+  public void flushScheduledReportsIfAble() {
+    CountDownLatch latch = new CountDownLatch(1);
+    new Thread(
+            () -> {
+              ForcedSender.sendBlockingWithPriority(transport, Priority.HIGHEST);
+              latch.countDown();
+            })
+        .start();
+    Utils.awaitUninterruptibly(latch, 2, TimeUnit.SECONDS);
+  }
+
   /** Send the report to Crashlytics through Google DataTransport. */
   private void sendReport(
       CrashlyticsReportWithSessionId reportWithSessionId,
@@ -128,6 +145,7 @@ private void sendReport(
             tcs.trySetException(error);
             return;
           }
+          flushScheduledReportsIfAble();
           tcs.trySetResult(reportWithSessionId);
         });
   }

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

@@ -0,0 +1,26 @@
+package com.google.android.datatransport.runtime;
+
+import android.annotation.SuppressLint;
+import androidx.annotation.Discouraged;
+import androidx.annotation.WorkerThread;
+import com.google.android.datatransport.Priority;
+import com.google.android.datatransport.Transport;
+
+@Discouraged(
+    message =
+        "TransportRuntime is not a realtime delivery system, don't use unless you absolutely must.")
+public final class ForcedSender {
+  @WorkerThread
+  public static void sendBlockingWithPriority(Transport<?> transport, Priority priority) {
+    @SuppressLint("DiscouragedApi")
+    TransportContext context = getTransportContextOrThrow(transport).withPriority(priority);
+    TransportRuntime.getInstance().getUploader().upload(context, 1, () -> {});
+  }
+
+  private static TransportContext getTransportContextOrThrow(Transport<?> transport) {
+    if (transport instanceof TransportImpl) {
+      return ((TransportImpl<?>) transport).getTransportContext();
+    }
+    throw new IllegalArgumentException("Expected instance of TransportImpl.");
+  }
+}

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

@@ -57,4 +57,8 @@ public void schedule(Event<T> event, TransportScheduleCallback callback) {
             .build(),
         callback);
   }
+
+  TransportContext getTransportContext() {
+    return transportContext;
+  }
 }

transport/transport-runtime/transport-runtime.gradle

@@ -101,7 +101,7 @@ thirdPartyLicenses {
 
 dependencies {
     implementation project(':transport:transport-api')
-    implementation 'androidx.annotation:annotation:1.1.0'
+    implementation 'androidx.annotation:annotation:1.3.0'
     implementation 'javax.inject:javax.inject:1'
     implementation project(":encoders:firebase-encoders")
     implementation project(":encoders:firebase-encoders-proto")
@@ -132,4 +132,4 @@ dependencies {
     androidTestImplementation 'org.mockito:mockito-android:2.25.0'
 
     androidTestAnnotationProcessor 'com.google.dagger:dagger-compiler:2.27'
-}
+}