Allow reserved metadata to be propagated between calls

src/ruby/ext/grpc/rb_channel.c

@@ -195,18 +195,28 @@ static VALUE grpc_rb_channel_init_copy(VALUE copy, VALUE orig) {
 
 /* Create a call given a grpc_channel, in order to call method. The request
    is not sent until grpc_call_invoke is called. */
-static VALUE grpc_rb_channel_create_call(VALUE self, VALUE cqueue, VALUE method,
-                                         VALUE host, VALUE deadline) {
+static VALUE grpc_rb_channel_create_call(VALUE self, VALUE cqueue,
+                                         VALUE parent, VALUE mask,
+                                         VALUE method, VALUE host,
+                                         VALUE deadline) {
   VALUE res = Qnil;
   grpc_rb_channel *wrapper = NULL;
   grpc_call *call = NULL;
+  grpc_call *parent_call = NULL;
   grpc_channel *ch = NULL;
   grpc_completion_queue *cq = NULL;
+  int flags = GRPC_PROPAGATE_DEFAULTS;
   char *method_chars = StringValueCStr(method);
   char *host_chars = NULL;
   if (host != Qnil) {
     host_chars = StringValueCStr(host);
   }
+  if (mask != Qnil) {
+    flags = NUM2UINT(mask);
+  }
+  if (parent != Qnil) {
+    parent_call = grpc_rb_get_wrapped_call(parent);
+  }
 
   cq = grpc_rb_get_wrapped_completion_queue(cqueue);
   TypedData_Get_Struct(self, grpc_rb_channel, &grpc_channel_data_type, wrapper);
@@ -216,10 +226,10 @@ static VALUE grpc_rb_channel_create_call(VALUE self, VALUE cqueue, VALUE method,
     return Qnil;
   }
 
-  call = grpc_channel_create_call(ch, NULL, GRPC_PROPAGATE_DEFAULTS, cq,
-                                  method_chars, host_chars,
-                                  grpc_rb_time_timeval(deadline,
-                                                       /* absolute time */ 0));
+  call = grpc_channel_create_call(ch, parent_call, flags, cq, method_chars,
+                                  host_chars, grpc_rb_time_timeval(
+                                      deadline,
+                                      /* absolute time */ 0));
   if (call == NULL) {
     rb_raise(rb_eRuntimeError, "cannot create call with method %s",
              method_chars);
@@ -237,6 +247,7 @@ static VALUE grpc_rb_channel_create_call(VALUE self, VALUE cqueue, VALUE method,
   return res;
 }
 
+
 /* Closes the channel, calling it's destroy method */
 static VALUE grpc_rb_channel_destroy(VALUE self) {
   grpc_rb_channel *wrapper = NULL;
@@ -283,7 +294,7 @@ void Init_grpc_channel() {
 
   /* Add ruby analogues of the Channel methods. */
   rb_define_method(grpc_rb_cChannel, "create_call",
-                   grpc_rb_channel_create_call, 4);
+                   grpc_rb_channel_create_call, 6);
   rb_define_method(grpc_rb_cChannel, "target", grpc_rb_channel_get_target, 0);
   rb_define_method(grpc_rb_cChannel, "destroy", grpc_rb_channel_destroy, 0);
   rb_define_alias(grpc_rb_cChannel, "close", "destroy");

src/ruby/lib/grpc/generic/client_stub.rb

@@ -32,6 +32,8 @@ require 'grpc/version'
 
 # GRPC contains the General RPC module.
 module GRPC
+  # rubocop:disable Metrics/ParameterLists
+
   # ClientStub represents an endpoint used to send requests to GRPC servers.
   class ClientStub
     include Core::StatusCodes
@@ -68,6 +70,12 @@ module GRPC
       update_metadata
     end
 
+    # Allows users of the stub to modify the propagate mask.
+    #
+    # This is an advanced feature for use when making calls to another gRPC
+    # server whilst running in the handler of an existing one.
+    attr_writer :propagate_mask
+
     # Creates a new ClientStub.
     #
     # Minimally, a stub is created with the just the host of the gRPC service
@@ -91,8 +99,8 @@ module GRPC
     #
     # - :update_metadata
     # when present, this a func that takes a hash and returns a hash
-    # it can be used to update metadata, i.e, remove, change or update
-    # amend metadata values.
+    # it can be used to update metadata, i.e, remove, or amend
+    # metadata values.
     #
     # @param host [String] the host the stub connects to
     # @param q [Core::CompletionQueue] used to wait for events
@@ -105,6 +113,7 @@ module GRPC
                    channel_override: nil,
                    timeout: nil,
                    creds: nil,
+                   propagate_mask: nil,
                    update_metadata: nil,
                    **kw)
       fail(TypeError, '!CompletionQueue') unless q.is_a?(Core::CompletionQueue)
@@ -113,6 +122,7 @@ module GRPC
       @update_metadata = ClientStub.check_update_metadata(update_metadata)
       alt_host = kw[Core::Channel::SSL_TARGET]
       @host = alt_host.nil? ? host : alt_host
+      @propagate_mask = propagate_mask
       @timeout = timeout.nil? ? DEFAULT_TIMEOUT : timeout
     end
 
@@ -151,11 +161,15 @@ module GRPC
     # @param marshal [Function] f(obj)->string that marshals requests
     # @param unmarshal [Function] f(string)->obj that unmarshals responses
     # @param timeout [Numeric] (optional) the max completion time in seconds
+    # @param parent [Core::Call] a prior call whose reserved metadata
+    #   will be propagated by this one.
     # @param return_op [true|false] return an Operation if true
     # @return [Object] the response received from the server
     def request_response(method, req, marshal, unmarshal, timeout = nil,
-                         return_op: false, **kw)
-      c = new_active_call(method, marshal, unmarshal, timeout)
+                         return_op: false,
+                         parent: parent,
+                         **kw)
+      c = new_active_call(method, marshal, unmarshal, timeout, parent: parent)
       kw_with_jwt_uri = self.class.update_with_jwt_aud_uri(kw, @host, method)
       md = @update_metadata.nil? ? kw : @update_metadata.call(kw_with_jwt_uri)
       return c.request_response(req, **md) unless return_op
@@ -210,10 +224,14 @@ module GRPC
     # @param unmarshal [Function] f(string)->obj that unmarshals responses
     # @param timeout [Numeric] the max completion time in seconds
     # @param return_op [true|false] return an Operation if true
+    # @param parent [Core::Call] a prior call whose reserved metadata
+    #   will be propagated by this one.
     # @return [Object|Operation] the response received from the server
     def client_streamer(method, requests, marshal, unmarshal, timeout = nil,
-                        return_op: false, **kw)
-      c = new_active_call(method, marshal, unmarshal, timeout)
+                        return_op: false,
+                        parent: nil,
+                        **kw)
+      c = new_active_call(method, marshal, unmarshal, timeout, parent: parent)
       kw_with_jwt_uri = self.class.update_with_jwt_aud_uri(kw, @host, method)
       md = @update_metadata.nil? ? kw : @update_metadata.call(kw_with_jwt_uri)
       return c.client_streamer(requests, **md) unless return_op
@@ -276,11 +294,16 @@ module GRPC
     # @param unmarshal [Function] f(string)->obj that unmarshals responses
     # @param timeout [Numeric] the max completion time in seconds
     # @param return_op [true|false]return an Operation if true
+    # @param parent [Core::Call] a prior call whose reserved metadata
+    #   will be propagated by this one.
     # @param blk [Block] when provided, is executed for each response
     # @return [Enumerator|Operation|nil] as discussed above
     def server_streamer(method, req, marshal, unmarshal, timeout = nil,
-                        return_op: false, **kw, &blk)
-      c = new_active_call(method, marshal, unmarshal, timeout)
+                        return_op: false,
+                        parent: nil,
+                        **kw,
+                        &blk)
+      c = new_active_call(method, marshal, unmarshal, timeout, parent: parent)
       kw_with_jwt_uri = self.class.update_with_jwt_aud_uri(kw, @host, method)
       md = @update_metadata.nil? ? kw : @update_metadata.call(kw_with_jwt_uri)
       return c.server_streamer(req, **md, &blk) unless return_op
@@ -381,12 +404,17 @@ module GRPC
     # @param marshal [Function] f(obj)->string that marshals requests
     # @param unmarshal [Function] f(string)->obj that unmarshals responses
     # @param timeout [Numeric] (optional) the max completion time in seconds
-    # @param blk [Block] when provided, is executed for each response
+    # @param parent [Core::Call] a prior call whose reserved metadata
+    #   will be propagated by this one.
     # @param return_op [true|false] return an Operation if true
+    # @param blk [Block] when provided, is executed for each response
     # @return [Enumerator|nil|Operation] as discussed above
     def bidi_streamer(method, requests, marshal, unmarshal, timeout = nil,
-                      return_op: false, **kw, &blk)
-      c = new_active_call(method, marshal, unmarshal, timeout)
+                      return_op: false,
+                      parent: nil,
+                      **kw,
+                      &blk)
+      c = new_active_call(method, marshal, unmarshal, timeout, parent: parent)
       kw_with_jwt_uri = self.class.update_with_jwt_aud_uri(kw, @host, method)
       md = @update_metadata.nil? ? kw : @update_metadata.call(kw_with_jwt_uri)
       return c.bidi_streamer(requests, **md, &blk) unless return_op
@@ -407,10 +435,17 @@ module GRPC
     # @param method [string] the method being called.
     # @param marshal [Function] f(obj)->string that marshals requests
     # @param unmarshal [Function] f(string)->obj that unmarshals responses
+    # @param parent [Grpc::Call] a parent call, available when calls are
+    #   made from server
     # @param timeout [TimeConst]
-    def new_active_call(method, marshal, unmarshal, timeout = nil)
+    def new_active_call(method, marshal, unmarshal, timeout = nil, parent: nil)
       deadline = from_relative_time(timeout.nil? ? @timeout : timeout)
-      call = @ch.create_call(@queue, method, nil, deadline)
+      call = @ch.create_call(@queue,
+                             parent, # parent call
+                             @propagate_mask, # propagation options
+                             method,
+                             nil, # host use nil,
+                             deadline)
       ActiveCall.new(call, @queue, marshal, unmarshal, deadline, started: false)
     end
   end

src/ruby/spec/call_spec.rb

@@ -137,7 +137,7 @@ describe GRPC::Core::Call do
   end
 
   def make_test_call
-    @ch.create_call(client_queue, 'dummy_method', nil, deadline)
+    @ch.create_call(client_queue, nil, nil, 'dummy_method', nil, deadline)
   end
 
   def deadline

src/ruby/spec/channel_spec.rb

@@ -117,7 +117,7 @@ describe GRPC::Core::Channel do
       deadline = Time.now + 5
 
       blk = proc do
-        ch.create_call(cq, 'dummy_method', nil, deadline)
+        ch.create_call(cq, nil, nil, 'dummy_method', nil, deadline)
       end
       expect(&blk).to_not raise_error
     end
@@ -128,7 +128,7 @@ describe GRPC::Core::Channel do
 
       deadline = Time.now + 5
       blk = proc do
-        ch.create_call(cq, 'dummy_method', nil, deadline)
+        ch.create_call(cq, nil, nil, 'dummy_method', nil, deadline)
       end
       expect(&blk).to raise_error(RuntimeError)
     end

src/ruby/spec/client_server_spec.rb

@@ -61,7 +61,7 @@ shared_context 'setup: tags' do
   end
 
   def new_client_call
-    @ch.create_call(@client_queue, '/method', nil, deadline)
+    @ch.create_call(@client_queue, nil, nil, '/method', nil, deadline)
   end
 end
 

src/ruby/spec/generic/active_call_spec.rb

@@ -338,7 +338,7 @@ describe GRPC::ActiveCall do
   end
 
   def make_test_call
-    @ch.create_call(@client_queue, '/method', nil, deadline)
+    @ch.create_call(@client_queue, nil, nil, '/method', nil, deadline)
   end
 
   def deadline