Copy channel args hash before appending ruby user agent

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

@@ -100,7 +100,7 @@ module GRPC
                    channel_args: {},
                    interceptors: [])
       @ch = ClientStub.setup_channel(channel_override, host, creds,
-                                     channel_args)
+                                     channel_args.dup)
       alt_host = channel_args[Core::Channel::SSL_TARGET]
       @host = alt_host.nil? ? host : alt_host
       @propagate_mask = propagate_mask

src/ruby/spec/user_agent_spec.rb

@@ -0,0 +1,74 @@
+# Copyright 2020 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.
+
+require 'spec_helper'
+
+# a test service that checks the cert of its peer
+class UserAgentEchoService
+  include GRPC::GenericService
+  rpc :an_rpc, EchoMsg, EchoMsg
+
+  def an_rpc(_req, call)
+    EchoMsg.new(msg: call.metadata['user-agent'])
+  end
+end
+
+UserAgentEchoServiceStub = UserAgentEchoService.rpc_stub_class
+
+describe 'user agent' do
+  RpcServer = GRPC::RpcServer
+
+  before(:all) do
+    server_opts = {
+      poll_period: 1
+    }
+    @srv = new_rpc_server_for_testing(**server_opts)
+    @port = @srv.add_http2_port('0.0.0.0:0', :this_port_is_insecure)
+    @srv.handle(UserAgentEchoService)
+    @srv_thd = Thread.new { @srv.run }
+    @srv.wait_till_running
+  end
+
+  after(:all) do
+    expect(@srv.stopped?).to be(false)
+    @srv.stop
+    @srv_thd.join
+  end
+
+  it 'client sends expected user agent' do
+    stub = UserAgentEchoServiceStub.new("localhost:#{@port}",
+                                        :this_channel_is_insecure,
+                                        {})
+    response = stub.an_rpc(EchoMsg.new)
+    expected_user_agent_prefix = "grpc-ruby/#{GRPC::VERSION}"
+    expect(response.msg.start_with?(expected_user_agent_prefix)).to be true
+    # check that the expected user agent prefix occurs in the real user agent exactly once
+    expect(response.msg.split(expected_user_agent_prefix).size).to eq 2
+  end
+
+  it 'user agent header does not grow when the same channel args hash is used across multiple stubs' do
+    shared_channel_args_hash = {}
+    10.times do
+      stub = UserAgentEchoServiceStub.new("localhost:#{@port}",
+                                          :this_channel_is_insecure,
+                                          channel_args: shared_channel_args_hash)
+      response = stub.an_rpc(EchoMsg.new)
+      puts "got echo response: #{response.msg}"
+      expected_user_agent_prefix = "grpc-ruby/#{GRPC::VERSION}"
+      expect(response.msg.start_with?(expected_user_agent_prefix)).to be true
+      # check that the expected user agent prefix occurs in the real user agent exactly once
+      expect(response.msg.split(expected_user_agent_prefix).size).to eq 2
+    end
+  end
+end