core: Assure that context cancellationCause is set (#9501)

core: Assure that context cancellationCause is set

Makes sure that whenever a context is in a cancelled state, we also have
a cancellationCause.

api/src/main/java/io/grpc/InternalStatus.java

@@ -16,6 +16,8 @@
 
 package io.grpc;
 
+import javax.annotation.Nullable;
+
 /**
  * Accesses internal data.  Do not use this.
  */
@@ -34,4 +36,14 @@ public final class InternalStatus {
    */
   @Internal
   public static final Metadata.Key<Status> CODE_KEY = Status.CODE_KEY;
+
+  /**
+   * Create a new {@link StatusRuntimeException} with the internal option of skipping the filling
+   * of the stack trace.
+   */
+  @Internal
+  public static final StatusRuntimeException asRuntimeException(Status status,
+      @Nullable Metadata trailers, boolean fillInStackTrace) {
+    return new StatusRuntimeException(status, trailers, fillInStackTrace);
+  }
 }

core/src/main/java/io/grpc/internal/ServerCallImpl.java

@@ -35,6 +35,7 @@ import io.grpc.CompressorRegistry;
 import io.grpc.Context;
 import io.grpc.DecompressorRegistry;
 import io.grpc.InternalDecompressorRegistry;
+import io.grpc.InternalStatus;
 import io.grpc.Metadata;
 import io.grpc.MethodDescriptor;
 import io.grpc.SecurityLevel;
@@ -368,19 +369,22 @@ final class ServerCallImpl<ReqT, RespT> extends ServerCall<ReqT, RespT> {
     }
 
     private void closedInternal(Status status) {
+      Throwable cancelCause = null;
       try {
         if (status.isOk()) {
           listener.onComplete();
         } else {
           call.cancelled = true;
           listener.onCancel();
+          // The status will not have a cause in all failure scenarios but we want to make sure
+          // we always cancel the context with one to keep the context cancelled state consistent.
+          cancelCause = InternalStatus.asRuntimeException(
+              Status.CANCELLED.withDescription("RPC cancelled"), null, false);
         }
       } finally {
         // Cancel context after delivering RPC closure notification to allow the application to
         // clean up and update any state based on whether onComplete or onCancel was called.
-        // Note that in failure situations JumpToApplicationThreadServerStreamListener has already
-        // closed the context. In these situations this cancel() call will be a no-op.
-        context.cancel(null);
+        context.cancel(cancelCause);
       }
     }
 

core/src/main/java/io/grpc/internal/ServerImpl.java

@@ -45,6 +45,7 @@ import io.grpc.InternalChannelz.SocketStats;
 import io.grpc.InternalInstrumented;
 import io.grpc.InternalLogId;
 import io.grpc.InternalServerInterceptors;
+import io.grpc.InternalStatus;
 import io.grpc.Metadata;
 import io.grpc.ServerCall;
 import io.grpc.ServerCallExecutorSupplier;
@@ -894,9 +895,18 @@ public final class ServerImpl extends io.grpc.Server implements InternalInstrume
       // For cancellations, promptly inform any users of the context that their work should be
       // aborted. Otherwise, we can wait until pending work is done.
       if (!status.isOk()) {
+        // Since status was not OK we know that the call did not complete and got cancelled. To
+        // reflect this on the context we need to close it with a cause exception. Since not every
+        // failed status has an exception we will create one here if needed.
+        Throwable cancelCause = status.getCause();
+        if (cancelCause == null) {
+          cancelCause = InternalStatus.asRuntimeException(
+              Status.CANCELLED.withDescription("RPC cancelled"), null, false);
+        }
+
         // The callExecutor might be busy doing user work. To avoid waiting, use an executor that
         // is not serializing.
-        cancelExecutor.execute(new ContextCloser(context, status.getCause()));
+        cancelExecutor.execute(new ContextCloser(context, cancelCause));
       }
       final Link link = PerfMark.linkOut();
 

core/src/test/java/io/grpc/internal/ServerCallImplTest.java

@@ -20,6 +20,7 @@ import static com.google.common.base.Charsets.UTF_8;
 import static io.grpc.internal.GrpcUtil.CONTENT_LENGTH_KEY;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
@@ -424,7 +425,7 @@ public class ServerCallImplTest {
 
     verify(callListener).onCancel();
     assertTrue(context.isCancelled());
-    assertNull(context.cancellationCause());
+    assertNotNull(context.cancellationCause());
   }
 
   @Test

core/src/test/java/io/grpc/internal/ServerImplTest.java

@@ -130,7 +130,7 @@ public class ServerImplTest {
   private static final Context.Key<String> SERVER_TRACER_ADDED_KEY = Context.key("tracer-added");
   private static final Context.CancellableContext SERVER_CONTEXT =
       Context.ROOT.withValue(SERVER_ONLY, "yes").withCancellation();
-  private static final FakeClock.TaskFilter CONTEXT_CLOSER_TASK_FITLER =
+  private static final FakeClock.TaskFilter CONTEXT_CLOSER_TASK_FILTER =
       new FakeClock.TaskFilter() {
         @Override
         public boolean shouldAccept(Runnable runnable) {
@@ -1085,7 +1085,7 @@ public class ServerImplTest {
     assertTrue(onHalfCloseCalled.get());
 
     streamListener.closed(Status.CANCELLED);
-    assertEquals(1, executor.numPendingTasks(CONTEXT_CLOSER_TASK_FITLER));
+    assertEquals(1, executor.numPendingTasks(CONTEXT_CLOSER_TASK_FILTER));
     assertEquals(2, executor.runDueTasks());
     assertTrue(onCancelCalled.get());
 
@@ -1179,10 +1179,11 @@ public class ServerImplTest {
     assertFalse(callReference.get().isCancelled());
     assertFalse(context.get().isCancelled());
     streamListener.closed(Status.CANCELLED);
-    assertEquals(1, executor.numPendingTasks(CONTEXT_CLOSER_TASK_FITLER));
+    assertEquals(1, executor.numPendingTasks(CONTEXT_CLOSER_TASK_FILTER));
     assertEquals(2, executor.runDueTasks());
     assertTrue(callReference.get().isCancelled());
     assertTrue(context.get().isCancelled());
+    assertThat(context.get().cancellationCause()).isNotNull();
     assertTrue(contextCancelled.get());
   }
 
@@ -1208,6 +1209,7 @@ public class ServerImplTest {
     assertEquals(1, executor.runDueTasks());
     assertFalse(callReference.get().isCancelled());
     assertTrue(context.get().isCancelled());
+    assertThat(context.get().cancellationCause()).isNull();
     assertTrue(contextCancelled.get());
   }
 
@@ -1228,6 +1230,7 @@ public class ServerImplTest {
     
     assertTrue(callReference.get().isCancelled());
     assertTrue(context.get().isCancelled());
+    assertThat(context.get().cancellationCause()).isNotNull();
     assertTrue(contextCancelled.get());
   }