commit 528fb6651cf6c19032e30dacdf437a3b7caf05e3
author Jan Tattermusch <jtattermusch@google.com> Thu May 12 08:38:41 2016 -0700
committer Jan Tattermusch <jtattermusch@google.com> Thu May 12 08:38:41 2016 -0700
tree 30acc3c43865ba916655fb873237970e82613ae4
parent 1acbe3e8a8cfa8d35843b0007b9cd79d91c62c16

improve channel behavior in shutdown situations

src/csharp/Grpc.Core/Channel.cs

diff --git a/src/csharp/Grpc.Core/Channel.cs b/src/csharp/Grpc.Core/Channel.cs
index 89981b1..93a6e6a 100644
--- a/src/csharp/Grpc.Core/Channel.cs
+++ b/src/csharp/Grpc.Core/Channel.cs
@@ -32,6 +32,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 
 using Grpc.Core.Internal;
@@ -51,6 +52,7 @@
 
         readonly object myLock = new object();
         readonly AtomicCounter activeCallCounter = new AtomicCounter();
+        readonly CancellationTokenSource shutdownTokenSource = new CancellationTokenSource();
 
         readonly string target;
         readonly GrpcEnvironment environment;
@@ -101,12 +103,13 @@
 
         /// <summary>
         /// Gets current connectivity state of this channel.
+        /// After channel is has been shutdown, <c>ChannelState.FatalFailure</c> will be returned.
         /// </summary>
         public ChannelState State
         {
             get
             {
-                return handle.CheckConnectivityState(false);        
+                return GetConnectivityState(false);
             }
         }
 
@@ -155,6 +158,17 @@
         }
 
         /// <summary>
+        /// Returns a token that gets cancelled once <c>ShutdownAsync</c> is invoked.
+        /// </summary>
+        public CancellationToken ShutdownToken
+        {
+            get
+            {
+                return this.shutdownTokenSource.Token;
+            }
+        }
+
+        /// <summary>
         /// Allows explicitly requesting channel to connect without starting an RPC.
         /// Returned task completes once state Ready was seen. If the deadline is reached,
         /// or channel enters the FatalFailure state, the task is cancelled.
@@ -164,7 +178,7 @@
         /// <param name="deadline">The deadline. <c>null</c> indicates no deadline.</param>
         public async Task ConnectAsync(DateTime? deadline = null)
         {
-            var currentState = handle.CheckConnectivityState(true);
+            var currentState = GetConnectivityState(true);
             while (currentState != ChannelState.Ready)
             {
                 if (currentState == ChannelState.FatalFailure)
@@ -172,7 +186,7 @@
                     throw new OperationCanceledException("Channel has reached FatalFailure state.");
                 }
                 await WaitForStateChangedAsync(currentState, deadline).ConfigureAwait(false);
-                currentState = handle.CheckConnectivityState(false);
+                currentState = GetConnectivityState(false);
             }
         }
 
@@ -188,6 +202,8 @@
                 shutdownRequested = true;
             }
 
+            shutdownTokenSource.Cancel();
+
             var activeCallCount = activeCallCounter.Count;
             if (activeCallCount > 0)
             {
@@ -231,6 +247,18 @@
             activeCallCounter.Decrement();
         }
 
+        private ChannelState GetConnectivityState(bool tryToConnect)
+        {
+            try
+            {
+                return handle.CheckConnectivityState(tryToConnect);
+            }
+            catch (ObjectDisposedException)
+            {
+                return ChannelState.FatalFailure;
+            }
+        }
+
         private static void EnsureUserAgentChannelOption(Dictionary<string, ChannelOption> options)
         {
             var key = ChannelOptions.PrimaryUserAgentString;