Merge pull request #16716 from yashykt/interceptors_initial

Create interfaces and initial plumbing for interception API

28 files changed, 398 insertions, 28 deletions

diff --git a/BUILD b/BUILD
index 0cd587a274..ff2cf8bbb3 100644
--- a/BUILD
+++ b/BUILD
@@ -1982,6 +1982,7 @@ grpc_cc_library(
         "include/grpcpp/impl/codegen/channel_interface.h",
         "include/grpcpp/impl/codegen/client_callback.h",
         "include/grpcpp/impl/codegen/client_context.h",
+        "include/grpcpp/impl/codegen/client_interceptor.h",
         "include/grpcpp/impl/codegen/client_unary_call.h",
         "include/grpcpp/impl/codegen/completion_queue.h",
         "include/grpcpp/impl/codegen/completion_queue_tag.h",
@@ -1989,6 +1990,7 @@ grpc_cc_library(
         "include/grpcpp/impl/codegen/core_codegen_interface.h",
         "include/grpcpp/impl/codegen/create_auth_context.h",
         "include/grpcpp/impl/codegen/grpc_library.h",
+        "include/grpcpp/impl/codegen/interceptor.h",
         "include/grpcpp/impl/codegen/metadata_map.h",
         "include/grpcpp/impl/codegen/method_handler_impl.h",
         "include/grpcpp/impl/codegen/rpc_method.h",
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9c91dd3664..dcd7adeebe 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3075,6 +3075,7 @@ foreach(_hdr
   include/grpcpp/impl/codegen/channel_interface.h
   include/grpcpp/impl/codegen/client_callback.h
   include/grpcpp/impl/codegen/client_context.h
+  include/grpcpp/impl/codegen/client_interceptor.h
   include/grpcpp/impl/codegen/client_unary_call.h
   include/grpcpp/impl/codegen/completion_queue.h
   include/grpcpp/impl/codegen/completion_queue_tag.h
@@ -3082,6 +3083,7 @@ foreach(_hdr
   include/grpcpp/impl/codegen/core_codegen_interface.h
   include/grpcpp/impl/codegen/create_auth_context.h
   include/grpcpp/impl/codegen/grpc_library.h
+  include/grpcpp/impl/codegen/interceptor.h
   include/grpcpp/impl/codegen/metadata_map.h
   include/grpcpp/impl/codegen/method_handler_impl.h
   include/grpcpp/impl/codegen/rpc_method.h
@@ -3644,6 +3646,7 @@ foreach(_hdr
   include/grpcpp/impl/codegen/channel_interface.h
   include/grpcpp/impl/codegen/client_callback.h
   include/grpcpp/impl/codegen/client_context.h
+  include/grpcpp/impl/codegen/client_interceptor.h
   include/grpcpp/impl/codegen/client_unary_call.h
   include/grpcpp/impl/codegen/completion_queue.h
   include/grpcpp/impl/codegen/completion_queue_tag.h
@@ -3651,6 +3654,7 @@ foreach(_hdr
   include/grpcpp/impl/codegen/core_codegen_interface.h
   include/grpcpp/impl/codegen/create_auth_context.h
   include/grpcpp/impl/codegen/grpc_library.h
+  include/grpcpp/impl/codegen/interceptor.h
   include/grpcpp/impl/codegen/metadata_map.h
   include/grpcpp/impl/codegen/method_handler_impl.h
   include/grpcpp/impl/codegen/rpc_method.h
@@ -4051,6 +4055,7 @@ foreach(_hdr
   include/grpcpp/impl/codegen/channel_interface.h
   include/grpcpp/impl/codegen/client_callback.h
   include/grpcpp/impl/codegen/client_context.h
+  include/grpcpp/impl/codegen/client_interceptor.h
   include/grpcpp/impl/codegen/client_unary_call.h
   include/grpcpp/impl/codegen/completion_queue.h
   include/grpcpp/impl/codegen/completion_queue_tag.h
@@ -4058,6 +4063,7 @@ foreach(_hdr
   include/grpcpp/impl/codegen/core_codegen_interface.h
   include/grpcpp/impl/codegen/create_auth_context.h
   include/grpcpp/impl/codegen/grpc_library.h
+  include/grpcpp/impl/codegen/interceptor.h
   include/grpcpp/impl/codegen/metadata_map.h
   include/grpcpp/impl/codegen/method_handler_impl.h
   include/grpcpp/impl/codegen/rpc_method.h
@@ -4230,6 +4236,7 @@ foreach(_hdr
   include/grpcpp/impl/codegen/channel_interface.h
   include/grpcpp/impl/codegen/client_callback.h
   include/grpcpp/impl/codegen/client_context.h
+  include/grpcpp/impl/codegen/client_interceptor.h
   include/grpcpp/impl/codegen/client_unary_call.h
   include/grpcpp/impl/codegen/completion_queue.h
   include/grpcpp/impl/codegen/completion_queue_tag.h
@@ -4237,6 +4244,7 @@ foreach(_hdr
   include/grpcpp/impl/codegen/core_codegen_interface.h
   include/grpcpp/impl/codegen/create_auth_context.h
   include/grpcpp/impl/codegen/grpc_library.h
+  include/grpcpp/impl/codegen/interceptor.h
   include/grpcpp/impl/codegen/metadata_map.h
   include/grpcpp/impl/codegen/method_handler_impl.h
   include/grpcpp/impl/codegen/rpc_method.h
@@ -4550,6 +4558,7 @@ foreach(_hdr
   include/grpcpp/impl/codegen/channel_interface.h
   include/grpcpp/impl/codegen/client_callback.h
   include/grpcpp/impl/codegen/client_context.h
+  include/grpcpp/impl/codegen/client_interceptor.h
   include/grpcpp/impl/codegen/client_unary_call.h
   include/grpcpp/impl/codegen/completion_queue.h
   include/grpcpp/impl/codegen/completion_queue_tag.h
@@ -4557,6 +4566,7 @@ foreach(_hdr
   include/grpcpp/impl/codegen/core_codegen_interface.h
   include/grpcpp/impl/codegen/create_auth_context.h
   include/grpcpp/impl/codegen/grpc_library.h
+  include/grpcpp/impl/codegen/interceptor.h
   include/grpcpp/impl/codegen/metadata_map.h
   include/grpcpp/impl/codegen/method_handler_impl.h
   include/grpcpp/impl/codegen/rpc_method.h
diff --git a/Makefile b/Makefile
index e86a0695be..67635ff8c2 100644
--- a/Makefile
+++ b/Makefile
@@ -5428,6 +5428,7 @@ PUBLIC_HEADERS_CXX += \
     include/grpcpp/impl/codegen/channel_interface.h \
     include/grpcpp/impl/codegen/client_callback.h \
     include/grpcpp/impl/codegen/client_context.h \
+    include/grpcpp/impl/codegen/client_interceptor.h \
     include/grpcpp/impl/codegen/client_unary_call.h \
     include/grpcpp/impl/codegen/completion_queue.h \
     include/grpcpp/impl/codegen/completion_queue_tag.h \
@@ -5435,6 +5436,7 @@ PUBLIC_HEADERS_CXX += \
     include/grpcpp/impl/codegen/core_codegen_interface.h \
     include/grpcpp/impl/codegen/create_auth_context.h \
     include/grpcpp/impl/codegen/grpc_library.h \
+    include/grpcpp/impl/codegen/interceptor.h \
     include/grpcpp/impl/codegen/metadata_map.h \
     include/grpcpp/impl/codegen/method_handler_impl.h \
     include/grpcpp/impl/codegen/rpc_method.h \
@@ -6006,6 +6008,7 @@ PUBLIC_HEADERS_CXX += \
     include/grpcpp/impl/codegen/channel_interface.h \
     include/grpcpp/impl/codegen/client_callback.h \
     include/grpcpp/impl/codegen/client_context.h \
+    include/grpcpp/impl/codegen/client_interceptor.h \
     include/grpcpp/impl/codegen/client_unary_call.h \
     include/grpcpp/impl/codegen/completion_queue.h \
     include/grpcpp/impl/codegen/completion_queue_tag.h \
@@ -6013,6 +6016,7 @@ PUBLIC_HEADERS_CXX += \
     include/grpcpp/impl/codegen/core_codegen_interface.h \
     include/grpcpp/impl/codegen/create_auth_context.h \
     include/grpcpp/impl/codegen/grpc_library.h \
+    include/grpcpp/impl/codegen/interceptor.h \
     include/grpcpp/impl/codegen/metadata_map.h \
     include/grpcpp/impl/codegen/method_handler_impl.h \
     include/grpcpp/impl/codegen/rpc_method.h \
@@ -6398,6 +6402,7 @@ PUBLIC_HEADERS_CXX += \
     include/grpcpp/impl/codegen/channel_interface.h \
     include/grpcpp/impl/codegen/client_callback.h \
     include/grpcpp/impl/codegen/client_context.h \
+    include/grpcpp/impl/codegen/client_interceptor.h \
     include/grpcpp/impl/codegen/client_unary_call.h \
     include/grpcpp/impl/codegen/completion_queue.h \
     include/grpcpp/impl/codegen/completion_queue_tag.h \
@@ -6405,6 +6410,7 @@ PUBLIC_HEADERS_CXX += \
     include/grpcpp/impl/codegen/core_codegen_interface.h \
     include/grpcpp/impl/codegen/create_auth_context.h \
     include/grpcpp/impl/codegen/grpc_library.h \
+    include/grpcpp/impl/codegen/interceptor.h \
     include/grpcpp/impl/codegen/metadata_map.h \
     include/grpcpp/impl/codegen/method_handler_impl.h \
     include/grpcpp/impl/codegen/rpc_method.h \
@@ -6554,6 +6560,7 @@ PUBLIC_HEADERS_CXX += \
     include/grpcpp/impl/codegen/channel_interface.h \
     include/grpcpp/impl/codegen/client_callback.h \
     include/grpcpp/impl/codegen/client_context.h \
+    include/grpcpp/impl/codegen/client_interceptor.h \
     include/grpcpp/impl/codegen/client_unary_call.h \
     include/grpcpp/impl/codegen/completion_queue.h \
     include/grpcpp/impl/codegen/completion_queue_tag.h \
@@ -6561,6 +6568,7 @@ PUBLIC_HEADERS_CXX += \
     include/grpcpp/impl/codegen/core_codegen_interface.h \
     include/grpcpp/impl/codegen/create_auth_context.h \
     include/grpcpp/impl/codegen/grpc_library.h \
+    include/grpcpp/impl/codegen/interceptor.h \
     include/grpcpp/impl/codegen/metadata_map.h \
     include/grpcpp/impl/codegen/method_handler_impl.h \
     include/grpcpp/impl/codegen/rpc_method.h \
@@ -6879,6 +6887,7 @@ PUBLIC_HEADERS_CXX += \
     include/grpcpp/impl/codegen/channel_interface.h \
     include/grpcpp/impl/codegen/client_callback.h \
     include/grpcpp/impl/codegen/client_context.h \
+    include/grpcpp/impl/codegen/client_interceptor.h \
     include/grpcpp/impl/codegen/client_unary_call.h \
     include/grpcpp/impl/codegen/completion_queue.h \
     include/grpcpp/impl/codegen/completion_queue_tag.h \
@@ -6886,6 +6895,7 @@ PUBLIC_HEADERS_CXX += \
     include/grpcpp/impl/codegen/core_codegen_interface.h \
     include/grpcpp/impl/codegen/create_auth_context.h \
     include/grpcpp/impl/codegen/grpc_library.h \
+    include/grpcpp/impl/codegen/interceptor.h \
     include/grpcpp/impl/codegen/metadata_map.h \
     include/grpcpp/impl/codegen/method_handler_impl.h \
     include/grpcpp/impl/codegen/rpc_method.h \
diff --git a/build.yaml b/build.yaml
index 3bc78d9299..6f81bf7afc 100644
--- a/build.yaml
+++ b/build.yaml
@@ -1171,6 +1171,7 @@ filegroups:
   - include/grpcpp/impl/codegen/channel_interface.h
   - include/grpcpp/impl/codegen/client_callback.h
   - include/grpcpp/impl/codegen/client_context.h
+  - include/grpcpp/impl/codegen/client_interceptor.h
   - include/grpcpp/impl/codegen/client_unary_call.h
   - include/grpcpp/impl/codegen/completion_queue.h
   - include/grpcpp/impl/codegen/completion_queue_tag.h
@@ -1178,6 +1179,7 @@ filegroups:
   - include/grpcpp/impl/codegen/core_codegen_interface.h
   - include/grpcpp/impl/codegen/create_auth_context.h
   - include/grpcpp/impl/codegen/grpc_library.h
+  - include/grpcpp/impl/codegen/interceptor.h
   - include/grpcpp/impl/codegen/metadata_map.h
   - include/grpcpp/impl/codegen/method_handler_impl.h
   - include/grpcpp/impl/codegen/rpc_method.h
diff --git a/gRPC-C++.podspec b/gRPC-C++.podspec
index b51c14eba9..f2d9a814c3 100644
--- a/gRPC-C++.podspec
+++ b/gRPC-C++.podspec
@@ -132,6 +132,7 @@ Pod::Spec.new do |s|
                       'include/grpcpp/impl/codegen/channel_interface.h',
                       'include/grpcpp/impl/codegen/client_callback.h',
                       'include/grpcpp/impl/codegen/client_context.h',
+                      'include/grpcpp/impl/codegen/client_interceptor.h',
                       'include/grpcpp/impl/codegen/client_unary_call.h',
                       'include/grpcpp/impl/codegen/completion_queue.h',
                       'include/grpcpp/impl/codegen/completion_queue_tag.h',
@@ -139,6 +140,7 @@ Pod::Spec.new do |s|
                       'include/grpcpp/impl/codegen/core_codegen_interface.h',
                       'include/grpcpp/impl/codegen/create_auth_context.h',
                       'include/grpcpp/impl/codegen/grpc_library.h',
+                      'include/grpcpp/impl/codegen/interceptor.h',
                       'include/grpcpp/impl/codegen/metadata_map.h',
                       'include/grpcpp/impl/codegen/method_handler_impl.h',
                       'include/grpcpp/impl/codegen/rpc_method.h',
diff --git a/include/grpcpp/channel.h b/include/grpcpp/channel.h
index f1dba5b8ad..b7c9e354de 100644
--- a/include/grpcpp/channel.h
+++ b/include/grpcpp/channel.h
@@ -24,6 +24,7 @@
 #include <grpc/grpc.h>
 #include <grpcpp/impl/call.h>
 #include <grpcpp/impl/codegen/channel_interface.h>
+#include <grpcpp/impl/codegen/client_interceptor.h>
 #include <grpcpp/impl/codegen/config.h>
 #include <grpcpp/impl/codegen/grpc_library.h>
 
@@ -62,8 +63,14 @@ class Channel final : public ChannelInterface,
   friend class internal::BlockingUnaryCallImpl;
   friend void experimental::ChannelResetConnectionBackoff(Channel* channel);
   friend std::shared_ptr<Channel> CreateChannelInternal(
-      const grpc::string& host, grpc_channel* c_channel);
-  Channel(const grpc::string& host, grpc_channel* c_channel);
+      const grpc::string& host, grpc_channel* c_channel,
+      std::unique_ptr<std::vector<
+          std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+          interceptor_creators);
+  Channel(const grpc::string& host, grpc_channel* c_channel,
+          std::unique_ptr<std::vector<
+              std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+              interceptor_creators);
 
   internal::Call CreateCall(const internal::RpcMethod& method,
                             ClientContext* context,
@@ -91,6 +98,9 @@ class Channel final : public ChannelInterface,
   // It is _not owned_ by the channel; ownership belongs with its internal
   // shutdown callback tag (invoked when the CQ is fully shutdown).
   CompletionQueue* callback_cq_ = nullptr;
+
+  std::vector<std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>
+      interceptor_creators_;
 };
 
 }  // namespace grpc
diff --git a/include/grpcpp/create_channel.h b/include/grpcpp/create_channel.h
index 7a505a7127..43188d09e7 100644
--- a/include/grpcpp/create_channel.h
+++ b/include/grpcpp/create_channel.h
@@ -22,6 +22,7 @@
 #include <memory>
 
 #include <grpcpp/channel.h>
+#include <grpcpp/impl/codegen/client_interceptor.h>
 #include <grpcpp/security/credentials.h>
 #include <grpcpp/support/channel_arguments.h>
 #include <grpcpp/support/config.h>
@@ -53,6 +54,26 @@ std::shared_ptr<Channel> CreateCustomChannel(
     const std::shared_ptr<ChannelCredentials>& creds,
     const ChannelArguments& args);
 
+namespace experimental {
+/// Create a new \em custom \a Channel pointing to \a target with \a
+/// interceptors being invoked per call.
+///
+/// \warning For advanced use and testing ONLY. Override default channel
+/// arguments only if necessary.
+///
+/// \param target The URI of the endpoint to connect to.
+/// \param creds Credentials to use for the created channel. If it does not
+/// hold an object or is invalid, a lame channel (one on which all operations
+/// fail) is returned.
+/// \param args Options for channel creation.
+std::shared_ptr<Channel> CreateCustomChannelWithInterceptors(
+    const grpc::string& target,
+    const std::shared_ptr<ChannelCredentials>& creds,
+    const ChannelArguments& args,
+    std::unique_ptr<std::vector<
+        std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+        interceptor_creators);
+}  // namespace experimental
 }  // namespace grpc
 
 #endif  // GRPCPP_CREATE_CHANNEL_H
diff --git a/include/grpcpp/create_channel_posix.h b/include/grpcpp/create_channel_posix.h
index 9bf5acc45c..808514041b 100644
--- a/include/grpcpp/create_channel_posix.h
+++ b/include/grpcpp/create_channel_posix.h
@@ -45,6 +45,23 @@ std::shared_ptr<Channel> CreateInsecureChannelFromFd(const grpc::string& target,
 std::shared_ptr<Channel> CreateCustomInsecureChannelFromFd(
     const grpc::string& target, int fd, const ChannelArguments& args);
 
+namespace experimental {
+
+/// Create a new \a Channel communicating over given file descriptor with custom
+/// channel arguments.
+///
+/// \param target The name of the target.
+/// \param fd The file descriptor representing a socket.
+/// \param args Options for channel creation.
+/// \param interceptor_creators Vector of interceptor factory objects.
+std::shared_ptr<Channel> CreateCustomInsecureChannelWithInterceptorsFromFd(
+    const grpc::string& target, int fd, const ChannelArguments& args,
+    std::unique_ptr<std::vector<
+        std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+        interceptor_creators);
+
+}  // namespace experimental
+
 #endif  // GPR_SUPPORT_CHANNELS_FROM_FD
 
 }  // namespace grpc
diff --git a/include/grpcpp/impl/codegen/client_interceptor.h b/include/grpcpp/impl/codegen/client_interceptor.h
new file mode 100644
index 0000000000..f460c5ac0c
--- /dev/null
+++ b/include/grpcpp/impl/codegen/client_interceptor.h
@@ -0,0 +1,44 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPCPP_IMPL_CODEGEN_CLIENT_INTERCEPTOR_H
+#define GRPCPP_IMPL_CODEGEN_CLIENT_INTERCEPTOR_H
+
+#include <grpcpp/impl/codegen/interceptor.h>
+
+namespace grpc {
+namespace experimental {
+class ClientInterceptor {
+ public:
+  virtual ~ClientInterceptor() {}
+
+  virtual void Intercept(InterceptorBatchMethods* methods) = 0;
+};
+
+class ClientRpcInfo {};
+
+class ClientInterceptorFactoryInterface {
+ public:
+  virtual ~ClientInterceptorFactoryInterface() {}
+  virtual ClientInterceptor* CreateClientInterceptor(ClientRpcInfo* info) = 0;
+};
+
+}  // namespace experimental
+}  // namespace grpc
+
+#endif  // GRPCPP_IMPL_CODEGEN_CLIENT_INTERCEPTOR_H
diff --git a/include/grpcpp/impl/codegen/interceptor.h b/include/grpcpp/impl/codegen/interceptor.h
new file mode 100644
index 0000000000..6402a3a946
--- /dev/null
+++ b/include/grpcpp/impl/codegen/interceptor.h
@@ -0,0 +1,67 @@
+/*
+ *
+ * Copyright 2018 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPCPP_IMPL_CODEGEN_INTERCEPTOR_H
+#define GRPCPP_IMPL_CODEGEN_INTERCEPTOR_H
+
+namespace grpc {
+namespace experimental {
+class InterceptedMessage {
+ public:
+  template <class M>
+  bool Extract(M* msg);  // returns false if definitely invalid extraction
+  template <class M>
+  M* MutableExtract();
+  uint64_t length();  // length on wire
+};
+
+enum class InterceptionHookPoints {
+  /* The first two in this list are for clients and servers */
+  PRE_SEND_INITIAL_METADATA,
+  PRE_SEND_MESSAGE,
+  PRE_SEND_STATUS /* server only */,
+  /* The following three are for hijacked clients only and can only be
+     registered by the global interceptor */
+  PRE_RECV_INITIAL_METADATA,
+  PRE_RECV_MESSAGE,
+  PRE_RECV_STATUS,
+  /* The following two are for all clients and servers */
+  POST_RECV_INITIAL_METADATA,
+  POST_RECV_MESSAGE,
+  POST_RECV_STATUS /* client only */,
+  POST_RECV_CLOSE /* server only */,
+  NUM_INTERCEPTION_HOOKS
+};
+
+class InterceptorBatchMethods {
+ public:
+  virtual ~InterceptorBatchMethods();
+  // Queries to check whether the current batch has an interception hook point
+  // of type \a type
+  virtual bool QueryInterceptionHookPoint(InterceptionHookPoints type) = 0;
+  // Calling this will signal that the interceptor is done intercepting the
+  // current batch of the RPC
+  virtual void Proceed() = 0;
+  // Calling this indicates that the interceptor has hijacked the RPC (only
+  // valid if the batch contains send_initial_metadata on the client side)
+  virtual void Hijack() = 0;
+};
+}  // namespace experimental
+}  // namespace grpc
+
+#endif  // GRPCPP_IMPL_CODEGEN_INTERCEPTOR_H
diff --git a/include/grpcpp/security/credentials.h b/include/grpcpp/security/credentials.h
index bfadc15df5..8dfbdec3e6 100644
--- a/include/grpcpp/security/credentials.h
+++ b/include/grpcpp/security/credentials.h
@@ -24,6 +24,7 @@
 #include <vector>
 
 #include <grpc/grpc_security_constants.h>
+#include <grpcpp/impl/codegen/client_interceptor.h>
 #include <grpcpp/impl/codegen/grpc_library.h>
 #include <grpcpp/security/auth_context.h>
 #include <grpcpp/support/status.h>
@@ -38,6 +39,18 @@ class SecureChannelCredentials;
 class CallCredentials;
 class SecureCallCredentials;
 
+class ChannelCredentials;
+
+namespace experimental {
+std::shared_ptr<Channel> CreateCustomChannelWithInterceptors(
+    const grpc::string& target,
+    const std::shared_ptr<ChannelCredentials>& creds,
+    const ChannelArguments& args,
+    std::unique_ptr<std::vector<
+        std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+        interceptor_creators);
+}  // namespace experimental
+
 /// A channel credentials object encapsulates all the state needed by a client
 /// to authenticate with a server for a given channel.
 /// It can make various assertions, e.g., about the client’s identity, role
@@ -62,8 +75,27 @@ class ChannelCredentials : private GrpcLibraryCodegen {
       const std::shared_ptr<ChannelCredentials>& creds,
       const ChannelArguments& args);
 
+  friend std::shared_ptr<Channel>
+  experimental::CreateCustomChannelWithInterceptors(
+      const grpc::string& target,
+      const std::shared_ptr<ChannelCredentials>& creds,
+      const ChannelArguments& args,
+      std::unique_ptr<std::vector<
+          std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+          interceptor_creators);
+
   virtual std::shared_ptr<Channel> CreateChannel(
       const grpc::string& target, const ChannelArguments& args) = 0;
+
+  // This function should have been a pure virtual function, but it is
+  // implemented as a virtual function so that it does not break API.
+  virtual std::shared_ptr<Channel> CreateChannelWithInterceptors(
+      const grpc::string& target, const ChannelArguments& args,
+      std::unique_ptr<std::vector<
+          std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+          interceptor_creators) {
+    return nullptr;
+  };
 };
 
 /// A call credentials object encapsulates the state needed by a client to
diff --git a/include/grpcpp/server.h b/include/grpcpp/server.h
index 72544c0f0b..8d3e856502 100644
--- a/include/grpcpp/server.h
+++ b/include/grpcpp/server.h
@@ -28,6 +28,7 @@
 #include <grpc/compression.h>
 #include <grpcpp/completion_queue.h>
 #include <grpcpp/impl/call.h>
+#include <grpcpp/impl/codegen/client_interceptor.h>
 #include <grpcpp/impl/codegen/grpc_library.h>
 #include <grpcpp/impl/codegen/server_interface.h>
 #include <grpcpp/impl/rpc_service_method.h>
@@ -99,6 +100,30 @@ class Server : public ServerInterface, private GrpcLibraryCodegen {
   /// Establish a channel for in-process communication
   std::shared_ptr<Channel> InProcessChannel(const ChannelArguments& args);
 
+  /// NOTE: class experimental_type is not part of the public API of this class.
+  /// TODO(yashykt): Integrate into public API when this is no longer
+  /// experimental.
+  class experimental_type {
+   public:
+    explicit experimental_type(Server* server) : server_(server) {}
+
+    /// Establish a channel for in-process communication with client
+    /// interceptors
+    std::shared_ptr<Channel> InProcessChannelWithInterceptors(
+        const ChannelArguments& args,
+        std::unique_ptr<std::vector<
+            std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+            interceptor_creators);
+
+   private:
+    Server* server_;
+  };
+
+  /// NOTE: The function experimental() is not stable public API. It is a view
+  /// to the experimental components of this class. It may be changed or removed
+  /// at any time.
+  experimental_type experimental() { return experimental_type(this); }
+
  protected:
   /// Register a service. This call does not take ownership of the service.
   /// The service must exist for the lifetime of the Server instance.
diff --git a/src/cpp/client/channel_cc.cc b/src/cpp/client/channel_cc.cc
index 31c02893b1..2cab41b3f5 100644
--- a/src/cpp/client/channel_cc.cc
+++ b/src/cpp/client/channel_cc.cc
@@ -51,8 +51,16 @@
 namespace grpc {
 
 static internal::GrpcLibraryInitializer g_gli_initializer;
-Channel::Channel(const grpc::string& host, grpc_channel* channel)
+Channel::Channel(
+    const grpc::string& host, grpc_channel* channel,
+    std::unique_ptr<std::vector<
+        std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+        interceptor_creators)
     : host_(host), c_channel_(channel) {
+  auto* vector = interceptor_creators.release();
+  if (vector != nullptr) {
+    interceptor_creators_ = std::move(*vector);
+  }
   g_gli_initializer.summon();
 }
 
diff --git a/src/cpp/client/create_channel.cc b/src/cpp/client/create_channel.cc
index 67a46ce0e1..efdff6c265 100644
--- a/src/cpp/client/create_channel.cc
+++ b/src/cpp/client/create_channel.cc
@@ -39,11 +39,43 @@ std::shared_ptr<Channel> CreateCustomChannel(
     const std::shared_ptr<ChannelCredentials>& creds,
     const ChannelArguments& args) {
   GrpcLibraryCodegen init_lib;  // We need to call init in case of a bad creds.
-  return creds ? creds->CreateChannel(target, args)
-               : CreateChannelInternal(
-                     "", grpc_lame_client_channel_create(
-                             nullptr, GRPC_STATUS_INVALID_ARGUMENT,
-                             "Invalid credentials."));
+  return creds
+             ? creds->CreateChannel(target, args)
+             : CreateChannelInternal("",
+                                     grpc_lame_client_channel_create(
+                                         nullptr, GRPC_STATUS_INVALID_ARGUMENT,
+                                         "Invalid credentials."),
+                                     nullptr);
 }
 
+namespace experimental {
+/// Create a new \em custom \a Channel pointing to \a target with \a
+/// interceptors being invoked per call.
+///
+/// \warning For advanced use and testing ONLY. Override default channel
+/// arguments only if necessary.
+///
+/// \param target The URI of the endpoint to connect to.
+/// \param creds Credentials to use for the created channel. If it does not
+/// hold an object or is invalid, a lame channel (one on which all operations
+/// fail) is returned.
+/// \param args Options for channel creation.
+std::shared_ptr<Channel> CreateCustomChannelWithInterceptors(
+    const grpc::string& target,
+    const std::shared_ptr<ChannelCredentials>& creds,
+    const ChannelArguments& args,
+    std::unique_ptr<std::vector<
+        std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+        interceptor_creators) {
+  return creds
+             ? creds->CreateChannelWithInterceptors(
+                   target, args, std::move(interceptor_creators))
+             : CreateChannelInternal("",
+                                     grpc_lame_client_channel_create(
+                                         nullptr, GRPC_STATUS_INVALID_ARGUMENT,
+                                         "Invalid credentials."),
+                                     nullptr);
+}
+}  // namespace experimental
+
 }  // namespace grpc
diff --git a/src/cpp/client/create_channel_internal.cc b/src/cpp/client/create_channel_internal.cc
index aa96edfcff..313d682aae 100644
--- a/src/cpp/client/create_channel_internal.cc
+++ b/src/cpp/client/create_channel_internal.cc
@@ -24,8 +24,12 @@ struct grpc_channel;
 
 namespace grpc {
 
-std::shared_ptr<Channel> CreateChannelInternal(const grpc::string& host,
-                                               grpc_channel* c_channel) {
-  return std::shared_ptr<Channel>(new Channel(host, c_channel));
+std::shared_ptr<Channel> CreateChannelInternal(
+    const grpc::string& host, grpc_channel* c_channel,
+    std::unique_ptr<std::vector<
+        std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+        interceptor_creators) {
+  return std::shared_ptr<Channel>(
+      new Channel(host, c_channel, std::move(interceptor_creators)));
 }
 }  // namespace grpc
diff --git a/src/cpp/client/create_channel_internal.h b/src/cpp/client/create_channel_internal.h
index 86e8167277..512fc22866 100644
--- a/src/cpp/client/create_channel_internal.h
+++ b/src/cpp/client/create_channel_internal.h
@@ -21,6 +21,7 @@
 
 #include <memory>
 
+#include <grpcpp/impl/codegen/client_interceptor.h>
 #include <grpcpp/support/config.h>
 
 struct grpc_channel;
@@ -28,8 +29,11 @@ struct grpc_channel;
 namespace grpc {
 class Channel;
 
-std::shared_ptr<Channel> CreateChannelInternal(const grpc::string& host,
-                                               grpc_channel* c_channel);
+std::shared_ptr<Channel> CreateChannelInternal(
+    const grpc::string& host, grpc_channel* c_channel,
+    std::unique_ptr<std::vector<
+        std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+        interceptor_creators);
 
 }  // namespace grpc
 
diff --git a/src/cpp/client/create_channel_posix.cc b/src/cpp/client/create_channel_posix.cc
index f9285c9b28..8d775e7a87 100644
--- a/src/cpp/client/create_channel_posix.cc
+++ b/src/cpp/client/create_channel_posix.cc
@@ -33,7 +33,8 @@ std::shared_ptr<Channel> CreateInsecureChannelFromFd(const grpc::string& target,
   internal::GrpcLibrary init_lib;
   init_lib.init();
   return CreateChannelInternal(
-      "", grpc_insecure_channel_create_from_fd(target.c_str(), fd, nullptr));
+      "", grpc_insecure_channel_create_from_fd(target.c_str(), fd, nullptr),
+      nullptr);
 }
 
 std::shared_ptr<Channel> CreateCustomInsecureChannelFromFd(
@@ -42,10 +43,31 @@ std::shared_ptr<Channel> CreateCustomInsecureChannelFromFd(
   init_lib.init();
   grpc_channel_args channel_args;
   args.SetChannelArgs(&channel_args);
-  return CreateChannelInternal("", grpc_insecure_channel_create_from_fd(
-                                       target.c_str(), fd, &channel_args));
+  return CreateChannelInternal(
+      "",
+      grpc_insecure_channel_create_from_fd(target.c_str(), fd, &channel_args),
+      nullptr);
+}
+
+namespace experimental {
+
+std::shared_ptr<Channel> CreateCustomInsecureChannelWithInterceptorsFromFd(
+    const grpc::string& target, int fd, const ChannelArguments& args,
+    std::unique_ptr<std::vector<
+        std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+        interceptor_creators) {
+  internal::GrpcLibrary init_lib;
+  init_lib.init();
+  grpc_channel_args channel_args;
+  args.SetChannelArgs(&channel_args);
+  return CreateChannelInternal(
+      "",
+      grpc_insecure_channel_create_from_fd(target.c_str(), fd, &channel_args),
+      std::move(interceptor_creators));
 }
 
+}  // namespace experimental
+
 #endif  // GPR_SUPPORT_CHANNELS_FROM_FD
 
 }  // namespace grpc
diff --git a/src/cpp/client/cronet_credentials.cc b/src/cpp/client/cronet_credentials.cc
index 5c65ad05ea..09a76b428c 100644
--- a/src/cpp/client/cronet_credentials.cc
+++ b/src/cpp/client/cronet_credentials.cc
@@ -31,16 +31,25 @@ class CronetChannelCredentialsImpl final : public ChannelCredentials {
 
   std::shared_ptr<grpc::Channel> CreateChannel(
       const string& target, const grpc::ChannelArguments& args) override {
-    grpc_channel_args channel_args;
-    args.SetChannelArgs(&channel_args);
-    return CreateChannelInternal(
-        "", grpc_cronet_secure_channel_create(engine_, target.c_str(),
-                                              &channel_args, nullptr));
+    return CreateChannelWithInterceptors(target, args, nullptr);
   }
 
   SecureChannelCredentials* AsSecureCredentials() override { return nullptr; }
 
  private:
+  std::shared_ptr<grpc::Channel> CreateChannelWithInterceptors(
+      const string& target, const grpc::ChannelArguments& args,
+      std::unique_ptr<std::vector<
+          std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+          interceptor_creators) override {
+    grpc_channel_args channel_args;
+    args.SetChannelArgs(&channel_args);
+    return CreateChannelInternal(
+        "",
+        grpc_cronet_secure_channel_create(engine_, target.c_str(),
+                                          &channel_args, nullptr),
+        std::move(interceptor_creators));
+  }
   void* engine_;
 };
 
diff --git a/src/cpp/client/insecure_credentials.cc b/src/cpp/client/insecure_credentials.cc
index 04dc5c0bcc..b816e0c59a 100644
--- a/src/cpp/client/insecure_credentials.cc
+++ b/src/cpp/client/insecure_credentials.cc
@@ -32,11 +32,20 @@ class InsecureChannelCredentialsImpl final : public ChannelCredentials {
  public:
   std::shared_ptr<grpc::Channel> CreateChannel(
       const string& target, const grpc::ChannelArguments& args) override {
+    return CreateChannelWithInterceptors(target, args, nullptr);
+  }
+
+  std::shared_ptr<grpc::Channel> CreateChannelWithInterceptors(
+      const string& target, const grpc::ChannelArguments& args,
+      std::unique_ptr<std::vector<
+          std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+          interceptor_creators) override {
     grpc_channel_args channel_args;
     args.SetChannelArgs(&channel_args);
     return CreateChannelInternal(
         "",
-        grpc_insecure_channel_create(target.c_str(), &channel_args, nullptr));
+        grpc_insecure_channel_create(target.c_str(), &channel_args, nullptr),
+        std::move(interceptor_creators));
   }
 
   SecureChannelCredentials* AsSecureCredentials() override { return nullptr; }
diff --git a/src/cpp/client/secure_credentials.cc b/src/cpp/client/secure_credentials.cc
index e48fbeb86d..d1cd78e755 100644
--- a/src/cpp/client/secure_credentials.cc
+++ b/src/cpp/client/secure_credentials.cc
@@ -36,12 +36,22 @@ SecureChannelCredentials::SecureChannelCredentials(
 
 std::shared_ptr<grpc::Channel> SecureChannelCredentials::CreateChannel(
     const string& target, const grpc::ChannelArguments& args) {
+  return CreateChannelWithInterceptors(target, args, nullptr);
+}
+
+std::shared_ptr<grpc::Channel>
+SecureChannelCredentials::CreateChannelWithInterceptors(
+    const string& target, const grpc::ChannelArguments& args,
+    std::unique_ptr<std::vector<
+        std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+        interceptor_creators) {
   grpc_channel_args channel_args;
   args.SetChannelArgs(&channel_args);
   return CreateChannelInternal(
       args.GetSslTargetNameOverride(),
       grpc_secure_channel_create(c_creds_, target.c_str(), &channel_args,
-                                 nullptr));
+                                 nullptr),
+      std::move(interceptor_creators));
 }
 
 SecureCallCredentials::SecureCallCredentials(grpc_call_credentials* c_creds)
diff --git a/src/cpp/client/secure_credentials.h b/src/cpp/client/secure_credentials.h
index 85cb54227c..bfb6e17ee9 100644
--- a/src/cpp/client/secure_credentials.h
+++ b/src/cpp/client/secure_credentials.h
@@ -36,9 +36,15 @@ class SecureChannelCredentials final : public ChannelCredentials {
 
   std::shared_ptr<grpc::Channel> CreateChannel(
       const string& target, const grpc::ChannelArguments& args) override;
+
   SecureChannelCredentials* AsSecureCredentials() override { return this; }
 
  private:
+  std::shared_ptr<grpc::Channel> CreateChannelWithInterceptors(
+      const string& target, const grpc::ChannelArguments& args,
+      std::unique_ptr<std::vector<
+          std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+          interceptor_creators) override;
   grpc_channel_credentials* const c_creds_;
 };
 
diff --git a/src/cpp/server/server_cc.cc b/src/cpp/server/server_cc.cc
index 36f7eb81f9..7c764f4bce 100644
--- a/src/cpp/server/server_cc.cc
+++ b/src/cpp/server/server_cc.cc
@@ -473,7 +473,21 @@ std::shared_ptr<Channel> Server::InProcessChannel(
     const ChannelArguments& args) {
   grpc_channel_args channel_args = args.c_channel_args();
   return CreateChannelInternal(
-      "inproc", grpc_inproc_channel_create(server_, &channel_args, nullptr));
+      "inproc", grpc_inproc_channel_create(server_, &channel_args, nullptr),
+      nullptr);
+}
+
+std::shared_ptr<Channel>
+Server::experimental_type::InProcessChannelWithInterceptors(
+    const ChannelArguments& args,
+    std::unique_ptr<std::vector<
+        std::unique_ptr<experimental::ClientInterceptorFactoryInterface>>>
+        interceptor_creators) {
+  grpc_channel_args channel_args = args.c_channel_args();
+  return CreateChannelInternal(
+      "inproc",
+      grpc_inproc_channel_create(server_->server_, &channel_args, nullptr),
+      std::move(interceptor_creators));
 }
 
 static grpc_server_register_method_payload_handling PayloadHandlingForMethod(
diff --git a/test/cpp/microbenchmarks/bm_call_create.cc b/test/cpp/microbenchmarks/bm_call_create.cc
index 9516b2e3e2..389b888084 100644
--- a/test/cpp/microbenchmarks/bm_call_create.cc
+++ b/test/cpp/microbenchmarks/bm_call_create.cc
@@ -133,8 +133,10 @@ static void BM_LameChannelCallCreateCpp(benchmark::State& state) {
   TrackCounters track_counters;
   auto stub =
       grpc::testing::EchoTestService::NewStub(grpc::CreateChannelInternal(
-          "", grpc_lame_client_channel_create(
-                  "localhost:1234", GRPC_STATUS_UNAUTHENTICATED, "blah")));
+          "",
+          grpc_lame_client_channel_create("localhost:1234",
+                                          GRPC_STATUS_UNAUTHENTICATED, "blah"),
+          nullptr));
   grpc::CompletionQueue cq;
   grpc::testing::EchoRequest send_request;
   grpc::testing::EchoResponse recv_response;
diff --git a/test/cpp/microbenchmarks/fullstack_fixtures.h b/test/cpp/microbenchmarks/fullstack_fixtures.h
index d390ae08f6..7188a2a28a 100644
--- a/test/cpp/microbenchmarks/fullstack_fixtures.h
+++ b/test/cpp/microbenchmarks/fullstack_fixtures.h
@@ -218,7 +218,7 @@ class EndpointPairFixture : public BaseFixture {
           "target", &c_args, GRPC_CLIENT_DIRECT_CHANNEL, client_transport_);
       grpc_chttp2_transport_start_reading(client_transport_, nullptr, nullptr);
 
-      channel_ = CreateChannelInternal("", channel);
+      channel_ = CreateChannelInternal("", channel, nullptr);
     }
   }
 
diff --git a/test/cpp/performance/writes_per_rpc_test.cc b/test/cpp/performance/writes_per_rpc_test.cc
index 0ea3181f7e..7b51260e5b 100644
--- a/test/cpp/performance/writes_per_rpc_test.cc
+++ b/test/cpp/performance/writes_per_rpc_test.cc
@@ -118,7 +118,7 @@ class EndpointPairFixture {
           "target", &c_args, GRPC_CLIENT_DIRECT_CHANNEL, transport);
       grpc_chttp2_transport_start_reading(transport, nullptr, nullptr);
 
-      channel_ = CreateChannelInternal("", channel);
+      channel_ = CreateChannelInternal("", channel, nullptr);
     }
   }
 
diff --git a/tools/doxygen/Doxyfile.c++ b/tools/doxygen/Doxyfile.c++
index 3b7fd1fa8e..97599be443 100644
--- a/tools/doxygen/Doxyfile.c++
+++ b/tools/doxygen/Doxyfile.c++
@@ -949,6 +949,7 @@ include/grpcpp/impl/codegen/callback_common.h \
 include/grpcpp/impl/codegen/channel_interface.h \
 include/grpcpp/impl/codegen/client_callback.h \
 include/grpcpp/impl/codegen/client_context.h \
+include/grpcpp/impl/codegen/client_interceptor.h \
 include/grpcpp/impl/codegen/client_unary_call.h \
 include/grpcpp/impl/codegen/completion_queue.h \
 include/grpcpp/impl/codegen/completion_queue_tag.h \
@@ -958,6 +959,7 @@ include/grpcpp/impl/codegen/core_codegen.h \
 include/grpcpp/impl/codegen/core_codegen_interface.h \
 include/grpcpp/impl/codegen/create_auth_context.h \
 include/grpcpp/impl/codegen/grpc_library.h \
+include/grpcpp/impl/codegen/interceptor.h \
 include/grpcpp/impl/codegen/metadata_map.h \
 include/grpcpp/impl/codegen/method_handler_impl.h \
 include/grpcpp/impl/codegen/proto_buffer_reader.h \
diff --git a/tools/doxygen/Doxyfile.c++.internal b/tools/doxygen/Doxyfile.c++.internal
index c1bcdfd3d0..c852b29fce 100644
--- a/tools/doxygen/Doxyfile.c++.internal
+++ b/tools/doxygen/Doxyfile.c++.internal
@@ -950,6 +950,7 @@ include/grpcpp/impl/codegen/callback_common.h \
 include/grpcpp/impl/codegen/channel_interface.h \
 include/grpcpp/impl/codegen/client_callback.h \
 include/grpcpp/impl/codegen/client_context.h \
+include/grpcpp/impl/codegen/client_interceptor.h \
 include/grpcpp/impl/codegen/client_unary_call.h \
 include/grpcpp/impl/codegen/completion_queue.h \
 include/grpcpp/impl/codegen/completion_queue_tag.h \
@@ -960,6 +961,7 @@ include/grpcpp/impl/codegen/core_codegen.h \
 include/grpcpp/impl/codegen/core_codegen_interface.h \
 include/grpcpp/impl/codegen/create_auth_context.h \
 include/grpcpp/impl/codegen/grpc_library.h \
+include/grpcpp/impl/codegen/interceptor.h \
 include/grpcpp/impl/codegen/metadata_map.h \
 include/grpcpp/impl/codegen/method_handler_impl.h \
 include/grpcpp/impl/codegen/proto_buffer_reader.h \
diff --git a/tools/run_tests/generated/sources_and_headers.json b/tools/run_tests/generated/sources_and_headers.json
index 3df0ff58dc..8749593ed5 100644
--- a/tools/run_tests/generated/sources_and_headers.json
+++ b/tools/run_tests/generated/sources_and_headers.json
@@ -11071,6 +11071,7 @@
       "include/grpcpp/impl/codegen/channel_interface.h", 
       "include/grpcpp/impl/codegen/client_callback.h", 
       "include/grpcpp/impl/codegen/client_context.h", 
+      "include/grpcpp/impl/codegen/client_interceptor.h", 
       "include/grpcpp/impl/codegen/client_unary_call.h", 
       "include/grpcpp/impl/codegen/completion_queue.h", 
       "include/grpcpp/impl/codegen/completion_queue_tag.h", 
@@ -11078,6 +11079,7 @@
       "include/grpcpp/impl/codegen/core_codegen_interface.h", 
       "include/grpcpp/impl/codegen/create_auth_context.h", 
       "include/grpcpp/impl/codegen/grpc_library.h", 
+      "include/grpcpp/impl/codegen/interceptor.h", 
       "include/grpcpp/impl/codegen/metadata_map.h", 
       "include/grpcpp/impl/codegen/method_handler_impl.h", 
       "include/grpcpp/impl/codegen/rpc_method.h", 
@@ -11139,6 +11141,7 @@
       "include/grpcpp/impl/codegen/channel_interface.h", 
       "include/grpcpp/impl/codegen/client_callback.h", 
       "include/grpcpp/impl/codegen/client_context.h", 
+      "include/grpcpp/impl/codegen/client_interceptor.h", 
       "include/grpcpp/impl/codegen/client_unary_call.h", 
       "include/grpcpp/impl/codegen/completion_queue.h", 
       "include/grpcpp/impl/codegen/completion_queue_tag.h", 
@@ -11146,6 +11149,7 @@
       "include/grpcpp/impl/codegen/core_codegen_interface.h", 
       "include/grpcpp/impl/codegen/create_auth_context.h", 
       "include/grpcpp/impl/codegen/grpc_library.h", 
+      "include/grpcpp/impl/codegen/interceptor.h", 
       "include/grpcpp/impl/codegen/metadata_map.h", 
       "include/grpcpp/impl/codegen/method_handler_impl.h", 
       "include/grpcpp/impl/codegen/rpc_method.h",