From c131d2dd147136caecf326ffa7ff007e9ffd0771 Mon Sep 17 00:00:00 2001
From: Kenji Kaneda <kaneda@squareup.com>
Date: Mon, 27 Mar 2017 16:20:56 -0700
Subject: [PATCH] core: Do not call startDeadlineTimer when is
 deadlineCancellationExecutor is null

We got a NullPointerException from ClientCallImpl#startDeadlineTimer
when a new Call is created after a Netty channel is terminated. Here
is a stacktrace:

INTERNAL: java.lang.NullPointerException
at io.grpc.internal.ClientCallImpl.startDeadlineTimer(ClientCallImpl.java:320)
at io.grpc.internal.ClientCallImpl.start(ClientCallImpl.java:253)

The following code snippet reproduces the bug:

```
ManagedChannel channel = NettyChannelBuilder.forAddress(host, port)
    .usePlaintext(true)
    .build();
channel.shutdown();

Thread.sleep(1000);

GreeterGrpc.GreeterBlockingStub stub =
GreeterGrpc.newBlockingStub(channel)
    .withDeadlineAfter(10, TimeUnit.SECONDS);
stub.sayHello(HelloRequest.newBuilder().setName("world").build());
```

The issue was that ClientCallImpl is created from RealChannel#newCall
*after* ManagedChannelImpl#maybeTerminateChannel is called and
scheduledExecutor is set to null. In such a scenario,
deadlineCancellationExecutor is set to null.

I think there are several ways to fix this, but one way would be to
just avoid calling startDeadlineTimer() when
deadlineCancellationExecutor is null. DelayedClientTransport will
create a FailingClientStream with Status.UNAVAILABLE and we will get

```
Exception in thread "main" io.grpc.StatusRuntimeException:
UNAVAILABLE: Channel has shutdown (reported by delayed transport)
```
---
 core/src/main/java/io/grpc/internal/ClientCallImpl.java | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/core/src/main/java/io/grpc/internal/ClientCallImpl.java b/core/src/main/java/io/grpc/internal/ClientCallImpl.java
index 76df05fcf1..6d9eb20007 100644
--- a/core/src/main/java/io/grpc/internal/ClientCallImpl.java
+++ b/core/src/main/java/io/grpc/internal/ClientCallImpl.java
@@ -249,7 +249,9 @@ final class ClientCallImpl<ReqT, RespT> extends ClientCall<ReqT, RespT>
     context.addListener(this, directExecutor());
     if (effectiveDeadline != null
         // If the context has the effective deadline, we don't need to schedule an extra task.
-        && context.getDeadline() != effectiveDeadline) {
+        && context.getDeadline() != effectiveDeadline
+        // If the channel has been terminated, we don't need to schedule an extra task.
+        && deadlineCancellationExecutor != null) {
       deadlineCancellationFuture = startDeadlineTimer(effectiveDeadline);
     }
     if (cancelListenersShouldBeRemoved) {