Merge github.com:grpc/grpc into fixit23

10 files changed, 169 insertions, 43 deletions

diff --git a/src/csharp/Grpc.Core.Tests/CallOptionsTest.cs b/src/csharp/Grpc.Core.Tests/CallOptionsTest.cs
index 99a2d47e6e..3c3b9f7745 100644
--- a/src/csharp/Grpc.Core.Tests/CallOptionsTest.cs
+++ b/src/csharp/Grpc.Core.Tests/CallOptionsTest.cs
@@ -67,6 +67,9 @@ namespace Grpc.Core.Tests
             var credentials = new FakeCallCredentials();
             Assert.AreSame(credentials, options.WithCredentials(credentials).Credentials);
 
+            var flags = CallFlags.WaitForReady | CallFlags.CacheableRequest;
+            Assert.AreEqual(flags, options.WithFlags(flags).Flags);
+
             // Check that the original instance is unchanged.
             Assert.IsNull(options.Headers);
             Assert.IsNull(options.Deadline);
@@ -74,6 +77,7 @@ namespace Grpc.Core.Tests
             Assert.IsNull(options.WriteOptions);
             Assert.IsNull(options.PropagationToken);
             Assert.IsNull(options.Credentials);
+            Assert.AreEqual(default(CallFlags), options.Flags);
         }
 
         [Test]
@@ -94,5 +98,16 @@ namespace Grpc.Core.Tests
             Assert.AreEqual(token, new CallOptions(propagationToken: propagationToken2).Normalize().CancellationToken);
             Assert.Throws(typeof(ArgumentException), () => new CallOptions(cancellationToken: token, propagationToken: propagationToken2).Normalize());
         }
+
+        [Test]
+        public void WaitForReady()
+        {
+            var callOptions = new CallOptions();
+            Assert.IsFalse(callOptions.IsWaitForReady);
+
+            Assert.AreEqual(CallFlags.WaitForReady, callOptions.WithWaitForReady().Flags);
+            Assert.IsTrue(callOptions.WithWaitForReady().IsWaitForReady);
+            Assert.IsFalse(callOptions.WithWaitForReady(true).WithWaitForReady(false).IsWaitForReady);
+        }
     }
 }
diff --git a/src/csharp/Grpc.Core.Tests/Internal/FakeNativeCall.cs b/src/csharp/Grpc.Core.Tests/Internal/FakeNativeCall.cs
index 909112a47c..fe067fe8b0 100644
--- a/src/csharp/Grpc.Core.Tests/Internal/FakeNativeCall.cs
+++ b/src/csharp/Grpc.Core.Tests/Internal/FakeNativeCall.cs
@@ -115,27 +115,27 @@ namespace Grpc.Core.Internal.Tests
             return "PEER";
         }
 
-        public void StartUnary(UnaryResponseClientHandler callback, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
+        public void StartUnary(UnaryResponseClientHandler callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             UnaryResponseClientHandler = callback;
         }
 
-        public void StartUnary(BatchContextSafeHandle ctx, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
+        public void StartUnary(BatchContextSafeHandle ctx, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             throw new NotImplementedException();
         }
 
-        public void StartClientStreaming(UnaryResponseClientHandler callback, MetadataArraySafeHandle metadataArray)
+        public void StartClientStreaming(UnaryResponseClientHandler callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             UnaryResponseClientHandler = callback;
         }
 
-        public void StartServerStreaming(ReceivedStatusOnClientHandler callback, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
+        public void StartServerStreaming(ReceivedStatusOnClientHandler callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             ReceivedStatusOnClientHandler = callback;
         }
 
-        public void StartDuplexStreaming(ReceivedStatusOnClientHandler callback, MetadataArraySafeHandle metadataArray)
+        public void StartDuplexStreaming(ReceivedStatusOnClientHandler callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             ReceivedStatusOnClientHandler = callback;
         }
diff --git a/src/csharp/Grpc.Core/CallOptions.cs b/src/csharp/Grpc.Core/CallOptions.cs
index 35548cfc96..ce43dae171 100644
--- a/src/csharp/Grpc.Core/CallOptions.cs
+++ b/src/csharp/Grpc.Core/CallOptions.cs
@@ -50,6 +50,7 @@ namespace Grpc.Core
         WriteOptions writeOptions;
         ContextPropagationToken propagationToken;
         CallCredentials credentials;
+        CallFlags flags;
 
         /// <summary>
         /// Creates a new instance of <c>CallOptions</c> struct.
@@ -69,6 +70,7 @@ namespace Grpc.Core
             this.writeOptions = writeOptions;
             this.propagationToken = propagationToken;
             this.credentials = credentials;
+            this.flags = default(CallFlags);
         }
 
         /// <summary>
@@ -126,6 +128,24 @@ namespace Grpc.Core
         }
 
         /// <summary>
+        /// If <c>true</c> and and channel is in <c>ChannelState.TransientFailure</c>, the call will attempt waiting for the channel to recover
+        /// instead of failing immediately (which is the default "FailFast" semantics).
+        /// Note: experimental API that can change or be removed without any prior notice.
+        /// </summary>
+        public bool IsWaitForReady
+        {
+            get { return (this.flags & CallFlags.WaitForReady) == CallFlags.WaitForReady; }
+        }
+
+        /// <summary>
+        /// Flags to use for this call.
+        /// </summary>
+        internal CallFlags Flags
+        {
+            get { return this.flags; }
+        }
+
+        /// <summary>
         /// Returns new instance of <see cref="CallOptions"/> with
         /// <c>Headers</c> set to the value provided. Values of all other fields are preserved.
         /// </summary>
@@ -198,6 +218,32 @@ namespace Grpc.Core
         }
 
         /// <summary>
+        /// Returns new instance of <see cref="CallOptions"/> with "WaitForReady" semantics enabled/disabled.
+        /// <see cref="IsWaitForReady"/>.
+        /// Note: experimental API that can change or be removed without any prior notice.
+        /// </summary>
+        public CallOptions WithWaitForReady(bool waitForReady = true)
+        {
+            if (waitForReady)
+            {
+                return WithFlags(this.flags | CallFlags.WaitForReady);
+            }
+            return WithFlags(this.flags & ~CallFlags.WaitForReady);
+        }
+
+        /// <summary>
+        /// Returns new instance of <see cref="CallOptions"/> with
+        /// <c>Flags</c> set to the value provided. Values of all other fields are preserved.
+        /// </summary>
+        /// <param name="flags">The call flags.</param>
+        internal CallOptions WithFlags(CallFlags flags)
+        {
+            var newOptions = this;
+            newOptions.flags = flags;
+            return newOptions;
+        }
+
+        /// <summary>
         /// Returns a new instance of <see cref="CallOptions"/> with 
         /// all previously unset values set to their defaults and deadline and cancellation
         /// token propagated when appropriate.
diff --git a/src/csharp/Grpc.Core/Grpc.Core.csproj b/src/csharp/Grpc.Core/Grpc.Core.csproj
index 51e627044f..5bfb978ca6 100644
--- a/src/csharp/Grpc.Core/Grpc.Core.csproj
+++ b/src/csharp/Grpc.Core/Grpc.Core.csproj
@@ -140,6 +140,7 @@
     <Compile Include="Logging\LogLevelFilterLogger.cs" />
     <Compile Include="Internal\RequestCallContextSafeHandle.cs" />
     <Compile Include="Utils\TaskUtils.cs" />
+    <Compile Include="Internal\CallFlags.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="Grpc.Core.project.json" />
@@ -153,4 +154,4 @@
       <Link>roots.pem</Link>
     </EmbeddedResource>
   </ItemGroup>
-</Project>
+</Project>
\ No newline at end of file
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCall.cs b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
index da45c4829d..1f738a3b6f 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCall.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
@@ -106,7 +106,7 @@ namespace Grpc.Core.Internal
                 using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 using (var ctx = BatchContextSafeHandle.Create())
                 {
-                    call.StartUnary(ctx, payload, metadataArray, GetWriteFlagsForCall());
+                    call.StartUnary(ctx, payload, GetWriteFlagsForCall(), metadataArray, details.Options.Flags);
 
                     var ev = cq.Pluck(ctx.Handle);
 
@@ -150,7 +150,7 @@ namespace Grpc.Core.Internal
                 unaryResponseTcs = new TaskCompletionSource<TResponse>();
                 using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartUnary(HandleUnaryResponse, payload, metadataArray, GetWriteFlagsForCall());
+                    call.StartUnary(HandleUnaryResponse, payload, GetWriteFlagsForCall(), metadataArray, details.Options.Flags);
                 }
                 return unaryResponseTcs.Task;
             }
@@ -174,7 +174,7 @@ namespace Grpc.Core.Internal
                 unaryResponseTcs = new TaskCompletionSource<TResponse>();
                 using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartClientStreaming(HandleUnaryResponse, metadataArray);
+                    call.StartClientStreaming(HandleUnaryResponse, metadataArray, details.Options.Flags);
                 }
 
                 return unaryResponseTcs.Task;
@@ -200,7 +200,7 @@ namespace Grpc.Core.Internal
                 streamingResponseCallFinishedTcs = new TaskCompletionSource<object>();
                 using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartServerStreaming(HandleFinished, payload, metadataArray, GetWriteFlagsForCall());
+                    call.StartServerStreaming(HandleFinished, payload, GetWriteFlagsForCall(), metadataArray, details.Options.Flags);
                 }
                 call.StartReceiveInitialMetadata(HandleReceivedResponseHeaders);
             }
@@ -222,7 +222,7 @@ namespace Grpc.Core.Internal
                 streamingResponseCallFinishedTcs = new TaskCompletionSource<object>();
                 using (var metadataArray = MetadataArraySafeHandle.Create(details.Options.Headers))
                 {
-                    call.StartDuplexStreaming(HandleFinished, metadataArray);
+                    call.StartDuplexStreaming(HandleFinished, metadataArray, details.Options.Flags);
                 }
                 call.StartReceiveInitialMetadata(HandleReceivedResponseHeaders);
             }
diff --git a/src/csharp/Grpc.Core/Internal/CallFlags.cs b/src/csharp/Grpc.Core/Internal/CallFlags.cs
new file mode 100644
index 0000000000..454fa9b1f4
--- /dev/null
+++ b/src/csharp/Grpc.Core/Internal/CallFlags.cs
@@ -0,0 +1,60 @@
+#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.Internal
+{
+    /// <summary>
+    /// Flags to enable special call behaviors (client-side only).
+    /// </summary>
+    [Flags]
+    internal enum CallFlags
+    {
+        /// <summary>
+        /// The call is idempotent (retrying the call doesn't change the outcome of the operation).
+        /// </summary>
+        IdempotentRequest = 0x10,
+
+        /// <summary>
+        /// If channel is in <c>ChannelState.TransientFailure</c>, attempt waiting for the channel to recover
+        /// instead of failing the call immediately.
+        /// </summary>
+        WaitForReady = 0x20,
+
+        /// <summary>
+        /// The call is cacheable. gRPC is free to use GET verb */
+        /// </summary>
+        CacheableRequest = 0x40
+    }
+}
diff --git a/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs b/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
index f817a61bce..6bfcc7fa74 100644
--- a/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
+++ b/src/csharp/Grpc.Core/Internal/CallSafeHandle.cs
@@ -63,50 +63,50 @@ namespace Grpc.Core.Internal
             Native.grpcsharp_call_set_credentials(this, credentials).CheckOk();
         }
 
-        public void StartUnary(UnaryResponseClientHandler callback, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
+        public void StartUnary(UnaryResponseClientHandler callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             using (completionQueue.NewScope())
             {
                 var ctx = BatchContextSafeHandle.Create();
                 completionQueue.CompletionRegistry.RegisterBatchCompletion(ctx, (success, context) => callback(success, context.GetReceivedStatusOnClient(), context.GetReceivedMessage(), context.GetReceivedInitialMetadata()));
-                Native.grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags)
+                Native.grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), writeFlags, metadataArray, callFlags)
                     .CheckOk();
             }
         }
 
-        public void StartUnary(BatchContextSafeHandle ctx, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
+        public void StartUnary(BatchContextSafeHandle ctx, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
-            Native.grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags)
+            Native.grpcsharp_call_start_unary(this, ctx, payload, new UIntPtr((ulong)payload.Length), writeFlags, metadataArray, callFlags)
                 .CheckOk();
         }
 
-        public void StartClientStreaming(UnaryResponseClientHandler callback, MetadataArraySafeHandle metadataArray)
+        public void StartClientStreaming(UnaryResponseClientHandler callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             using (completionQueue.NewScope())
             {
                 var ctx = BatchContextSafeHandle.Create();
                 completionQueue.CompletionRegistry.RegisterBatchCompletion(ctx, (success, context) => callback(success, context.GetReceivedStatusOnClient(), context.GetReceivedMessage(), context.GetReceivedInitialMetadata()));
-                Native.grpcsharp_call_start_client_streaming(this, ctx, metadataArray).CheckOk();
+                Native.grpcsharp_call_start_client_streaming(this, ctx, metadataArray, callFlags).CheckOk();
             }
         }
 
-        public void StartServerStreaming(ReceivedStatusOnClientHandler callback, byte[] payload, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags)
+        public void StartServerStreaming(ReceivedStatusOnClientHandler callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             using (completionQueue.NewScope())
             {
                 var ctx = BatchContextSafeHandle.Create();
                 completionQueue.CompletionRegistry.RegisterBatchCompletion(ctx, (success, context) => callback(success, context.GetReceivedStatusOnClient()));
-                Native.grpcsharp_call_start_server_streaming(this, ctx, payload, new UIntPtr((ulong)payload.Length), metadataArray, writeFlags).CheckOk();
+                Native.grpcsharp_call_start_server_streaming(this, ctx, payload, new UIntPtr((ulong)payload.Length), writeFlags, metadataArray, callFlags).CheckOk();
             }
         }
 
-        public void StartDuplexStreaming(ReceivedStatusOnClientHandler callback, MetadataArraySafeHandle metadataArray)
+        public void StartDuplexStreaming(ReceivedStatusOnClientHandler callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags)
         {
             using (completionQueue.NewScope())
             {
                 var ctx = BatchContextSafeHandle.Create();
                 completionQueue.CompletionRegistry.RegisterBatchCompletion(ctx, (success, context) => callback(success, context.GetReceivedStatusOnClient()));
-                Native.grpcsharp_call_start_duplex_streaming(this, ctx, metadataArray).CheckOk();
+                Native.grpcsharp_call_start_duplex_streaming(this, ctx, metadataArray, callFlags).CheckOk();
             }
         }
 
diff --git a/src/csharp/Grpc.Core/Internal/INativeCall.cs b/src/csharp/Grpc.Core/Internal/INativeCall.cs
index cd3719cb50..94fbb08feb 100644
--- a/src/csharp/Grpc.Core/Internal/INativeCall.cs
+++ b/src/csharp/Grpc.Core/Internal/INativeCall.cs
@@ -31,6 +31,7 @@
 #endregion
 
 using System;
+using Grpc.Core;
 
 namespace Grpc.Core.Internal
 {
@@ -54,19 +55,19 @@ namespace Grpc.Core.Internal
     {
         void Cancel();
 
-        void CancelWithStatus(Grpc.Core.Status status);
+        void CancelWithStatus(Status status);
 
         string GetPeer();
 
-        void StartUnary(UnaryResponseClientHandler callback, byte[] payload, MetadataArraySafeHandle metadataArray, Grpc.Core.WriteFlags writeFlags);
+        void StartUnary(UnaryResponseClientHandler callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags);
 
-        void StartUnary(BatchContextSafeHandle ctx, byte[] payload, MetadataArraySafeHandle metadataArray, Grpc.Core.WriteFlags writeFlags);
+        void StartUnary(BatchContextSafeHandle ctx, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags);
 
-        void StartClientStreaming(UnaryResponseClientHandler callback, MetadataArraySafeHandle metadataArray);
+        void StartClientStreaming(UnaryResponseClientHandler callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags);
 
-        void StartServerStreaming(ReceivedStatusOnClientHandler callback, byte[] payload, MetadataArraySafeHandle metadataArray, Grpc.Core.WriteFlags writeFlags);
+        void StartServerStreaming(ReceivedStatusOnClientHandler callback, byte[] payload, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags callFlags);
 
-        void StartDuplexStreaming(ReceivedStatusOnClientHandler callback, MetadataArraySafeHandle metadataArray);
+        void StartDuplexStreaming(ReceivedStatusOnClientHandler callback, MetadataArraySafeHandle metadataArray, CallFlags callFlags);
 
         void StartReceiveMessage(ReceivedMessageHandler callback);
 
@@ -74,11 +75,11 @@ namespace Grpc.Core.Internal
 
         void StartSendInitialMetadata(SendCompletionHandler callback, MetadataArraySafeHandle metadataArray);
 
-        void StartSendMessage(SendCompletionHandler callback, byte[] payload, Grpc.Core.WriteFlags writeFlags, bool sendEmptyInitialMetadata);
+        void StartSendMessage(SendCompletionHandler callback, byte[] payload, WriteFlags writeFlags, bool sendEmptyInitialMetadata);
 
         void StartSendCloseFromClient(SendCompletionHandler callback);
 
-        void StartSendStatusFromServer(SendCompletionHandler callback, Grpc.Core.Status status, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata, byte[] optionalPayload, Grpc.Core.WriteFlags writeFlags);
+        void StartSendStatusFromServer(SendCompletionHandler callback, Status status, MetadataArraySafeHandle metadataArray, bool sendEmptyInitialMetadata, byte[] optionalPayload, WriteFlags writeFlags);
 
         void StartServerSide(ReceivedCloseOnServerHandler callback);
     }
diff --git a/src/csharp/Grpc.Core/Internal/NativeMethods.cs b/src/csharp/Grpc.Core/Internal/NativeMethods.cs
index 40ba7e30cb..ce38e37093 100644
--- a/src/csharp/Grpc.Core/Internal/NativeMethods.cs
+++ b/src/csharp/Grpc.Core/Internal/NativeMethods.cs
@@ -325,14 +325,14 @@ namespace Grpc.Core.Internal
             public delegate CallError grpcsharp_call_cancel_delegate(CallSafeHandle call);
             public delegate CallError grpcsharp_call_cancel_with_status_delegate(CallSafeHandle call, StatusCode status, string description);
             public delegate CallError grpcsharp_call_start_unary_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
+                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, WriteFlags writeFlags, MetadataArraySafeHandle metadataArray, CallFlags metadataFlags);
             public delegate CallError grpcsharp_call_start_client_streaming_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray);
+                BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray, CallFlags metadataFlags);
             public delegate CallError grpcsharp_call_start_server_streaming_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen,
-                MetadataArraySafeHandle metadataArray, WriteFlags writeFlags);
+                BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, WriteFlags writeFlags,
+                MetadataArraySafeHandle metadataArray, CallFlags metadataFlags);
             public delegate CallError grpcsharp_call_start_duplex_streaming_delegate(CallSafeHandle call,
-                BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray);
+                BatchContextSafeHandle ctx, MetadataArraySafeHandle metadataArray, CallFlags metadataFlags);
             public delegate CallError grpcsharp_call_send_message_delegate(CallSafeHandle call,
                 BatchContextSafeHandle ctx, byte[] sendBuffer, UIntPtr sendBufferLen, WriteFlags writeFlags, bool sendEmptyInitialMetadata);
             public delegate CallError grpcsharp_call_send_close_from_client_delegate(CallSafeHandle call,
diff --git a/src/csharp/ext/grpc_csharp_ext.c b/src/csharp/ext/grpc_csharp_ext.c
index 37d04eb100..946f5872c0 100644
--- a/src/csharp/ext/grpc_csharp_ext.c
+++ b/src/csharp/ext/grpc_csharp_ext.c
@@ -521,8 +521,8 @@ GPR_EXPORT void GPR_CALLTYPE grpcsharp_call_destroy(grpc_call *call) {
 
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_start_unary(grpc_call *call, grpcsharp_batch_context *ctx,
-                           const char *send_buffer, size_t send_buffer_len,
-                           grpc_metadata_array *initial_metadata, uint32_t write_flags) {
+                           const char *send_buffer, size_t send_buffer_len, uint32_t write_flags,
+                           grpc_metadata_array *initial_metadata, uint32_t initial_metadata_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[6];
   memset(ops, 0, sizeof(ops));
@@ -532,7 +532,7 @@ grpcsharp_call_start_unary(grpc_call *call, grpcsharp_batch_context *ctx,
   ops[0].data.send_initial_metadata.count = ctx->send_initial_metadata.count;
   ops[0].data.send_initial_metadata.metadata =
       ctx->send_initial_metadata.metadata;
-  ops[0].flags = 0;
+  ops[0].flags = initial_metadata_flags;
   ops[0].reserved = NULL;
 
   ops[1].op = GRPC_OP_SEND_MESSAGE;
@@ -575,7 +575,8 @@ grpcsharp_call_start_unary(grpc_call *call, grpcsharp_batch_context *ctx,
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_start_client_streaming(grpc_call *call,
                                       grpcsharp_batch_context *ctx,
-                                      grpc_metadata_array *initial_metadata) {
+                                      grpc_metadata_array *initial_metadata,
+                                      uint32_t initial_metadata_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[4];
   memset(ops, 0, sizeof(ops));
@@ -585,7 +586,7 @@ grpcsharp_call_start_client_streaming(grpc_call *call,
   ops[0].data.send_initial_metadata.count = ctx->send_initial_metadata.count;
   ops[0].data.send_initial_metadata.metadata =
       ctx->send_initial_metadata.metadata;
-  ops[0].flags = 0;
+  ops[0].flags = initial_metadata_flags;
   ops[0].reserved = NULL;
 
   ops[1].op = GRPC_OP_RECV_INITIAL_METADATA;
@@ -617,7 +618,8 @@ grpcsharp_call_start_client_streaming(grpc_call *call,
 
 GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_start_server_streaming(
     grpc_call *call, grpcsharp_batch_context *ctx, const char *send_buffer,
-    size_t send_buffer_len, grpc_metadata_array *initial_metadata, uint32_t write_flags) {
+    size_t send_buffer_len, uint32_t write_flags,
+    grpc_metadata_array *initial_metadata, uint32_t initial_metadata_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[4];
   memset(ops, 0, sizeof(ops));
@@ -627,7 +629,7 @@ GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_start_server_streaming(
   ops[0].data.send_initial_metadata.count = ctx->send_initial_metadata.count;
   ops[0].data.send_initial_metadata.metadata =
       ctx->send_initial_metadata.metadata;
-  ops[0].flags = 0;
+  ops[0].flags = initial_metadata_flags;
   ops[0].reserved = NULL;
 
   ops[1].op = GRPC_OP_SEND_MESSAGE;
@@ -660,7 +662,8 @@ GPR_EXPORT grpc_call_error GPR_CALLTYPE grpcsharp_call_start_server_streaming(
 GPR_EXPORT grpc_call_error GPR_CALLTYPE
 grpcsharp_call_start_duplex_streaming(grpc_call *call,
                                       grpcsharp_batch_context *ctx,
-                                      grpc_metadata_array *initial_metadata) {
+                                      grpc_metadata_array *initial_metadata,
+                                      uint32_t initial_metadata_flags) {
   /* TODO: don't use magic number */
   grpc_op ops[2];
   memset(ops, 0, sizeof(ops));
@@ -670,7 +673,7 @@ grpcsharp_call_start_duplex_streaming(grpc_call *call,
   ops[0].data.send_initial_metadata.count = ctx->send_initial_metadata.count;
   ops[0].data.send_initial_metadata.metadata =
       ctx->send_initial_metadata.metadata;
-  ops[0].flags = 0;
+  ops[0].flags = initial_metadata_flags;
   ops[0].reserved = NULL;
 
   ops[1].op = GRPC_OP_RECV_STATUS_ON_CLIENT;