C++ context propagation

4 files changed, 77 insertions, 5 deletions

diff --git a/include/grpc++/client_context.h b/include/grpc++/client_context.h
index 10c967d85b..1f40629e8d 100644
--- a/include/grpc++/client_context.h
+++ b/include/grpc++/client_context.h
@@ -39,6 +39,7 @@
 #include <string>
 
 #include <grpc/compression.h>
+#include <grpc/grpc.h>
 #include <grpc/support/log.h>
 #include <grpc/support/time.h>
 #include <grpc++/auth_context.h>
@@ -46,8 +47,6 @@
 #include <grpc++/status.h>
 #include <grpc++/time.h>
 
-struct grpc_call;
-struct grpc_completion_queue;
 struct census_context;
 
 namespace grpc {
@@ -70,12 +69,68 @@ template <class R, class W>
 class ClientAsyncReaderWriter;
 template <class R>
 class ClientAsyncResponseReader;
+class ServerContext;
+
+class PropagationOptions {
+ public:
+  PropagationOptions() : propagate_(GRPC_PROPAGATE_DEFAULTS) {}
+
+  PropagationOptions& enable_deadline_propagation() {
+    propagate_ |= GRPC_PROPAGATE_DEADLINE;
+    return *this;
+  }
+
+  PropagationOptions& disable_deadline_propagation() {
+    propagate_ &= ~GRPC_PROPAGATE_DEADLINE;
+    return *this;
+  }
+
+  PropagationOptions& enable_stats_propagation() {
+    propagate_ |= GRPC_PROPAGATE_STATS_CONTEXT;
+    return *this;
+  }
+
+  PropagationOptions& disable_stats_propagation() {
+    propagate_ &= ~GRPC_PROPAGATE_STATS_CONTEXT;
+    return *this;
+  }
+
+  PropagationOptions& enable_tracing_propagation() {
+    propagate_ |= GRPC_PROPAGATE_TRACING_CONTEXT;
+    return *this;
+  }
+
+  PropagationOptions& disable_tracing_propagation() {
+    propagate_ &= ~GRPC_PROPAGATE_TRACING_CONTEXT;
+    return *this;
+  }
+
+  PropagationOptions& enable_cancellation_propagation() {
+    propagate_ |= GRPC_PROPAGATE_CANCELLATION;
+    return *this;
+  }
+
+  PropagationOptions& disable_cancellation_propagation() {
+    propagate_ &= ~GRPC_PROPAGATE_CANCELLATION;
+    return *this;
+  }
+
+  gpr_uint32 c_bitmask() const { return propagate_; }
+
+ private:
+  gpr_uint32 propagate_;
+};
 
 class ClientContext {
  public:
   ClientContext();
   ~ClientContext();
 
+  /// Create a new ClientContext that propagates some or all of its attributes
+  static ClientContext FromServerContext(
+      const ServerContext& server_context,
+      PropagationOptions options = PropagationOptions());
+
   void AddMetadata(const grpc::string& meta_key,
                    const grpc::string& meta_value);
 
@@ -181,6 +236,9 @@ class ClientContext {
   std::multimap<grpc::string, grpc::string> recv_initial_metadata_;
   std::multimap<grpc::string, grpc::string> trailing_metadata_;
 
+  grpc_call* propagate_from_call_;
+  PropagationOptions propagation_options_;
+
   grpc_compression_algorithm compression_algorithm_;
 };
 
diff --git a/include/grpc++/server_context.h b/include/grpc++/server_context.h
index 23273f43e6..4f7fc54ef1 100644
--- a/include/grpc++/server_context.h
+++ b/include/grpc++/server_context.h
@@ -50,6 +50,7 @@ struct census_context;
 
 namespace grpc {
 
+class ClientContext;
 template <class W, class R>
 class ServerAsyncReader;
 template <class W>
@@ -158,6 +159,7 @@ class ServerContext {
   friend class ServerStreamingHandler;
   template <class ServiceType, class RequestType, class ResponseType>
   friend class BidiStreamingHandler;
+  friend class ::grpc::ClientContext;
 
   // Prevent copying.
   ServerContext(const ServerContext&);
diff --git a/src/cpp/client/channel.cc b/src/cpp/client/channel.cc
index 1912e5e4c8..5f54e7fcc1 100644
--- a/src/cpp/client/channel.cc
+++ b/src/cpp/client/channel.cc
@@ -63,10 +63,12 @@ Call Channel::CreateCall(const RpcMethod& method, ClientContext* context,
   const char* host_str = host_.empty() ? NULL : host_.c_str();
   auto c_call = method.channel_tag() && context->authority().empty()
                     ? grpc_channel_create_registered_call(
-                          c_channel_, NULL, GRPC_PROPAGATE_DEFAULTS, cq->cq(),
+                          c_channel_, context->propagate_from_call_,
+                          context->propagation_options_.c_bitmask(), cq->cq(),
                           method.channel_tag(), context->raw_deadline())
                     : grpc_channel_create_call(
-                          c_channel_, NULL, GRPC_PROPAGATE_DEFAULTS, cq->cq(),
+                          c_channel_, context->propagate_from_call_,
+                          context->propagation_options_.c_bitmask(), cq->cq(),
                           method.name(), context->authority().empty()
                                              ? host_str
                                              : context->authority().c_str(),
diff --git a/src/cpp/client/client_context.cc b/src/cpp/client/client_context.cc
index c38d0c1df6..80b6393f01 100644
--- a/src/cpp/client/client_context.cc
+++ b/src/cpp/client/client_context.cc
@@ -37,6 +37,7 @@
 #include <grpc/support/alloc.h>
 #include <grpc/support/string_util.h>
 #include <grpc++/credentials.h>
+#include <grpc++/server_context.h>
 #include <grpc++/time.h>
 
 #include "src/core/channel/compress_filter.h"
@@ -48,7 +49,8 @@ ClientContext::ClientContext()
     : initial_metadata_received_(false),
       call_(nullptr),
       cq_(nullptr),
-      deadline_(gpr_inf_future(GPR_CLOCK_REALTIME)) {}
+      deadline_(gpr_inf_future(GPR_CLOCK_REALTIME)),
+      propagate_from_call_(nullptr) {}
 
 ClientContext::~ClientContext() {
   if (call_) {
@@ -64,6 +66,14 @@ ClientContext::~ClientContext() {
   }
 }
 
+ClientContext ClientContext::FromServerContext(const ServerContext& context,
+                                               PropagationOptions options) {
+  ClientContext ctx;
+  ctx.propagate_from_call_ = context.call_;
+  ctx.propagation_options_ = options;
+  return ctx;
+}
+
 void ClientContext::AddMetadata(const grpc::string& meta_key,
                                 const grpc::string& meta_value) {
   send_initial_metadata_.insert(std::make_pair(meta_key, meta_value));