Added channel state API

10 files changed, 280 insertions, 9 deletions

diff --git a/src/csharp/Grpc.Auth/OAuth2Interceptors.cs b/src/csharp/Grpc.Auth/OAuth2Interceptors.cs
index c785ca5a16..cc9d2c175f 100644
--- a/src/csharp/Grpc.Auth/OAuth2Interceptors.cs
+++ b/src/csharp/Grpc.Auth/OAuth2Interceptors.cs
@@ -119,7 +119,5 @@ namespace Grpc.Auth
                 return new Metadata.Entry(AuthorizationHeader, Schema + " " + accessToken);
             }
         }
-
-
     }
 }
diff --git a/src/csharp/Grpc.Core.Tests/ChannelTest.cs b/src/csharp/Grpc.Core.Tests/ChannelTest.cs
new file mode 100644
index 0000000000..bfe001b292
--- /dev/null
+++ b/src/csharp/Grpc.Core.Tests/ChannelTest.cs
@@ -0,0 +1,82 @@
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using Grpc.Core;
+using Grpc.Core.Internal;
+using Grpc.Core.Utils;
+using NUnit.Framework;
+
+namespace Grpc.Core.Tests
+{
+    public class ChannelTest
+    {
+        [TestFixtureTearDown]
+        public void CleanupClass()
+        {
+            GrpcEnvironment.Shutdown();
+        }
+
+        [Test]
+        public void Constructor_RejectsInvalidParams()
+        {
+            Assert.Throws(typeof(NullReferenceException), () => new Channel(null, Credentials.Insecure));
+        }
+
+        [Test]
+        public void State_IdleAfterCreation()
+        {
+            using (var channel = new Channel("localhost", Credentials.Insecure))
+            {
+                Assert.AreEqual(ChannelState.Idle, channel.State);
+            }
+        }
+
+        [Test]
+        public void WaitForStateChangedAsync_InvalidArgument()
+        {
+            using (var channel = new Channel("localhost", Credentials.Insecure))
+            {
+                Assert.Throws(typeof(ArgumentException), () => channel.WaitForStateChangedAsync(ChannelState.FatalFailure));
+            }
+        }
+
+        [Test]
+        public void Dispose_IsIdempotent()
+        {
+            var channel = new Channel("localhost", Credentials.Insecure);
+            channel.Dispose();
+            channel.Dispose();
+        }
+    }
+}
diff --git a/src/csharp/Grpc.Core.Tests/ClientServerTest.cs b/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
index 540fe756c0..35924868ca 100644
--- a/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
+++ b/src/csharp/Grpc.Core.Tests/ClientServerTest.cs
@@ -276,6 +276,30 @@ namespace Grpc.Core.Tests
             Assert.IsTrue(peer.Contains(Host));
         }
 
+        [Test]
+        public async Task Channel_WaitForStateChangedAsync()
+        {
+            Assert.Throws(typeof(TaskCanceledException), 
+                async () => await channel.WaitForStateChangedAsync(channel.State, DateTime.UtcNow.AddMilliseconds(10)));
+
+            var stateChangedTask = channel.WaitForStateChangedAsync(channel.State);
+
+            var internalCall = new Call<string, string>(ServiceName, EchoMethod, channel, Metadata.Empty);
+            await Calls.AsyncUnaryCall(internalCall, "abc", CancellationToken.None);
+
+            await stateChangedTask;
+            Assert.AreEqual(ChannelState.Ready, channel.State);
+        }
+
+        [Test]
+        public async Task Channel_ConnectAsync()
+        {
+            await channel.ConnectAsync();
+            Assert.AreEqual(ChannelState.Ready, channel.State);
+            await channel.ConnectAsync(DateTime.UtcNow.AddMilliseconds(1000));
+            Assert.AreEqual(ChannelState.Ready, channel.State);
+        }
+
         private static async Task<string> EchoHandler(string request, ServerCallContext context)
         {
             foreach (Metadata.Entry metadataEntry in context.RequestHeaders)
diff --git a/src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj b/src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj
index 242a60d098..f2bf459dc5 100644
--- a/src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj
+++ b/src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj
@@ -76,6 +76,7 @@
     <Compile Include="Internal\TimespecTest.cs" />
     <Compile Include="TimeoutsTest.cs" />
     <Compile Include="NUnitVersionTest.cs" />
+    <Compile Include="ChannelTest.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <ItemGroup>
diff --git a/src/csharp/Grpc.Core.Tests/NUnitVersionTest.cs b/src/csharp/Grpc.Core.Tests/NUnitVersionTest.cs
index 600df1a18d..3fa6ad09c0 100644
--- a/src/csharp/Grpc.Core.Tests/NUnitVersionTest.cs
+++ b/src/csharp/Grpc.Core.Tests/NUnitVersionTest.cs
@@ -70,10 +70,8 @@ namespace Grpc.Core.Tests
         [Test]
         public async Task NUnitVersionTest2()
         {
-            testRunCount ++;
+            testRunCount++;
             await Task.Delay(10);
         }
-
-
     }
 }
diff --git a/src/csharp/Grpc.Core/Channel.cs b/src/csharp/Grpc.Core/Channel.cs
index 18e6f2fda5..8a71afa01a 100644
--- a/src/csharp/Grpc.Core/Channel.cs
+++ b/src/csharp/Grpc.Core/Channel.cs
@@ -37,6 +37,8 @@ using System.Threading;
 using System.Threading.Tasks;
 
 using Grpc.Core.Internal;
+using Grpc.Core.Logging;
+using Grpc.Core.Utils;
 
 namespace Grpc.Core
 {
@@ -45,6 +47,8 @@ namespace Grpc.Core
     /// </summary>
     public class Channel : IDisposable
     {
+        static readonly ILogger Logger = GrpcEnvironment.Logger.ForType<Channel>();
+
         readonly GrpcEnvironment environment;
         readonly ChannelSafeHandle handle;
         readonly List<ChannelOption> options;
@@ -53,13 +57,14 @@ namespace Grpc.Core
 
         /// <summary>
         /// Creates a channel that connects to a specific host.
-        /// Port will default to 80 for an unsecure channel and to 443 a secure channel.
+        /// Port will default to 80 for an unsecure channel and to 443 for a secure channel.
         /// </summary>
-        /// <param name="host">The DNS name of IP address of the host.</param>
+        /// <param name="host">The name or IP address of the host.</param>
         /// <param name="credentials">Credentials to secure the channel.</param>
         /// <param name="options">Channel options.</param>
         public Channel(string host, Credentials credentials, IEnumerable<ChannelOption> options = null)
         {
+            Preconditions.CheckNotNull(host);
             this.environment = GrpcEnvironment.GetInstance();
             this.options = options != null ? new List<ChannelOption>(options) : new List<ChannelOption>();
 
@@ -82,8 +87,8 @@ namespace Grpc.Core
         /// <summary>
         /// Creates a channel that connects to a specific host and port.
         /// </summary>
-        /// <param name="host">DNS name or IP address</param>
-        /// <param name="port">the port</param>
+        /// <param name="host">The name or IP address of the host.</param>
+        /// <param name="port">The port.</param>
         /// <param name="credentials">Credentials to secure the channel.</param>
         /// <param name="options">Channel options.</param>
         public Channel(string host, int port, Credentials credentials, IEnumerable<ChannelOption> options = null) :
@@ -91,6 +96,67 @@ namespace Grpc.Core
         {
         }
 
+        /// <summary>
+        /// Gets current connectivity state of this channel.
+        /// </summary>
+        public ChannelState State
+        {
+            get
+            {
+                return handle.CheckConnectivityState(false);        
+            }
+        }
+
+        /// <summary>
+        /// Returned tasks completes once channel state has become different from 
+        /// given lastObservedState. 
+        /// If deadline is reached or and error occurs, returned task is cancelled.
+        /// </summary>
+        public Task WaitForStateChangedAsync(ChannelState lastObservedState, DateTime? deadline = null)
+        {
+            Preconditions.CheckArgument(lastObservedState != ChannelState.FatalFailure,
+                "FatalFailure is a terminal state. No further state changes can occur.");
+            var tcs = new TaskCompletionSource<object>();
+            var deadlineTimespec = deadline.HasValue ? Timespec.FromDateTime(deadline.Value) : Timespec.InfFuture;
+            var handler = new BatchCompletionDelegate((success, ctx) =>
+            {
+                if (success)
+                {
+                    tcs.SetResult(null);
+                }
+                else
+                {
+                    tcs.SetCanceled();
+                }
+            });
+            handle.WatchConnectivityState(lastObservedState, deadlineTimespec, environment.CompletionQueue, environment.CompletionRegistry, handler);
+            return tcs.Task;
+        }
+
+        /// <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.
+        /// There is no need to call this explicitly unless your use case requires that.
+        /// Starting an RPC on a new channel will request connection implicitly.
+        /// </summary>
+        public async Task ConnectAsync(DateTime? deadline = null)
+        {
+            var currentState = handle.CheckConnectivityState(true);
+            while (currentState != ChannelState.Ready)
+            {
+                if (currentState == ChannelState.FatalFailure)
+                {
+                    throw new OperationCanceledException("Channel has reached FatalFailure state.");
+                }
+                await WaitForStateChangedAsync(currentState, deadline);
+                currentState = handle.CheckConnectivityState(false);
+            }
+        }
+
+        /// <summary>
+        /// Destroys the underlying channel.
+        /// </summary>
         public void Dispose()
         {
             Dispose(true);
diff --git a/src/csharp/Grpc.Core/ChannelState.cs b/src/csharp/Grpc.Core/ChannelState.cs
new file mode 100644
index 0000000000..d293b98f75
--- /dev/null
+++ b/src/csharp/Grpc.Core/ChannelState.cs
@@ -0,0 +1,69 @@
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+
+namespace Grpc.Core
+{
+    /// <summary>
+    /// Connectivity state of a channel.
+    /// Based on grpc_connectivity_state from grpc/grpc.h
+    /// </summary>
+    public enum ChannelState
+    {
+        /// <summary>
+        /// Channel is idle
+        /// </summary>
+        Idle,
+
+        /// <summary>
+        /// Channel is connecting
+        /// </summary>
+        Connecting,
+
+        /// <summary>
+        /// Channel is ready for work
+        /// </summary>
+        Ready,
+
+        /// <summary>
+        /// Channel has seen a failure but expects to recover
+        /// </summary>
+        TransientFailure,
+
+        /// <summary>
+        /// Channel has seen a failure that it cannot recover from
+        /// </summary>
+        FatalFailure
+    }
+}
diff --git a/src/csharp/Grpc.Core/Grpc.Core.csproj b/src/csharp/Grpc.Core/Grpc.Core.csproj
index 940a6b8ac0..641b54baba 100644
--- a/src/csharp/Grpc.Core/Grpc.Core.csproj
+++ b/src/csharp/Grpc.Core/Grpc.Core.csproj
@@ -115,6 +115,7 @@
     <Compile Include="Logging\ILogger.cs" />
     <Compile Include="Logging\ConsoleLogger.cs" />
     <Compile Include="Internal\NativeLogRedirector.cs" />
+    <Compile Include="ChannelState.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="Grpc.Core.nuspec" />
diff --git a/src/csharp/Grpc.Core/Internal/ChannelSafeHandle.cs b/src/csharp/Grpc.Core/Internal/ChannelSafeHandle.cs
index 20815efbd3..c017560b56 100644
--- a/src/csharp/Grpc.Core/Internal/ChannelSafeHandle.cs
+++ b/src/csharp/Grpc.Core/Internal/ChannelSafeHandle.cs
@@ -50,6 +50,13 @@ namespace Grpc.Core.Internal
         static extern CallSafeHandle grpcsharp_channel_create_call(ChannelSafeHandle channel, CompletionQueueSafeHandle cq, string method, string host, Timespec deadline);
 
         [DllImport("grpc_csharp_ext.dll")]
+        static extern ChannelState grpcsharp_channel_check_connectivity_state(ChannelSafeHandle channel, int tryToConnect);
+
+        [DllImport("grpc_csharp_ext.dll")]
+        static extern void grpcsharp_channel_watch_connectivity_state(ChannelSafeHandle channel, ChannelState lastObservedState,
+            Timespec deadline, CompletionQueueSafeHandle cq, BatchContextSafeHandle ctx);
+
+        [DllImport("grpc_csharp_ext.dll")]
         static extern void grpcsharp_channel_destroy(IntPtr channel);
 
         private ChannelSafeHandle()
@@ -73,6 +80,19 @@ namespace Grpc.Core.Internal
             return result;
         }
 
+        public ChannelState CheckConnectivityState(bool tryToConnect)
+        {
+            return grpcsharp_channel_check_connectivity_state(this, tryToConnect ? 1 : 0);
+        }
+
+        public void WatchConnectivityState(ChannelState lastObservedState, Timespec deadline, CompletionQueueSafeHandle cq,
+            CompletionRegistry completionRegistry, BatchCompletionDelegate callback)
+        {
+            var ctx = BatchContextSafeHandle.Create();
+            completionRegistry.RegisterBatchCompletion(ctx, callback);
+            grpcsharp_channel_watch_connectivity_state(this, lastObservedState, deadline, cq, ctx);
+        }
+
         protected override bool ReleaseHandle()
         {
             grpcsharp_channel_destroy(handle);
diff --git a/src/csharp/ext/grpc_csharp_ext.c b/src/csharp/ext/grpc_csharp_ext.c
index 49a0471042..0e3a83d244 100644
--- a/src/csharp/ext/grpc_csharp_ext.c
+++ b/src/csharp/ext/grpc_csharp_ext.c
@@ -382,6 +382,18 @@ grpcsharp_channel_create_call(grpc_channel *channel, grpc_completion_queue *cq,
   return grpc_channel_create_call(channel, cq, method, host, deadline);
 }
 
+GPR_EXPORT grpc_connectivity_state GPR_CALLTYPE
+grpcsharp_channel_check_connectivity_state(grpc_channel *channel, gpr_int32 try_to_connect) {
+  return grpc_channel_check_connectivity_state(channel, try_to_connect);
+}
+
+GPR_EXPORT void GPR_CALLTYPE grpcsharp_channel_watch_connectivity_state(
+    grpc_channel *channel, grpc_connectivity_state last_observed_state,
+    gpr_timespec deadline, grpc_completion_queue *cq, grpcsharp_batch_context *ctx) {
+  grpc_channel_watch_connectivity_state(channel, last_observed_state, NULL,
+                                        deadline, cq, ctx);
+}
+
 /* Channel args */
 
 GPR_EXPORT grpc_channel_args *GPR_CALLTYPE