fix: batch-requests: read trailer headers if exist (#9289)

diff --git a/apisix/plugins/batch-requests.lua b/apisix/plugins/batch-requests.lua
index 54dfba0..a1b5743 100644
--- a/apisix/plugins/batch-requests.lua
+++ b/apisix/plugins/batch-requests.lua
@@ -275,7 +275,14 @@
             headers = resp.headers,
         }
         if resp.has_body then
-            sub_resp.body = resp:read_body()
+            local err
+            sub_resp.body, err = resp:read_body()
+            if err then
+                sub_resp.read_body_err = err
+                core.log.error("read pipeline response body failed: ", err)
+            else
+                resp:read_trailers()
+            end
         end
         core.table.insert(aggregated_resp, sub_resp)
     end
diff --git a/t/plugin/batch-requests-grpc.t b/t/plugin/batch-requests-grpc.t
new file mode 100644
index 0000000..4acd500
--- /dev/null
+++ b/t/plugin/batch-requests-grpc.t
@@ -0,0 +1,205 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You 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.
+#
+use t::APISIX 'no_plan';
+
+repeat_each(1);
+no_long_string();
+no_root_location();
+
+add_block_preprocessor(sub {
+    my ($block) = @_;
+
+    if (!$block->request) {
+        $block->set_value("request", "GET /t");
+    }
+
+    if (!$block->no_error_log && !$block->error_log) {
+        $block->set_value("no_error_log", "[error]\n[alert]");
+    }
+
+    my $extra_yaml_config = <<_EOC_;
+plugins:
+    - grpc-transcode
+    - public-api
+    - batch-requests
+_EOC_
+
+    $block->set_value("extra_yaml_config", $extra_yaml_config);
+});
+
+run_tests;
+
+__DATA__
+
+=== TEST 1: pre-create public API route
+--- config
+    location /t {
+        content_by_lua_block {
+            local t = require("lib.test_admin").test
+            local code, body = t('/apisix/admin/routes/1',
+                 ngx.HTTP_PUT,
+                 [[{
+                        "plugins": {
+                            "public-api": {}
+                        },
+                        "uri": "/apisix/batch-requests"
+                 }]]
+                )
+
+            if code >= 300 then
+                ngx.status = code
+            end
+            ngx.say(body)
+        }
+    }
+--- response_body
+passed
+
+
+
+=== TEST 2: set proto(id: 1)
+--- config
+    location /t {
+        content_by_lua_block {
+            local t = require("lib.test_admin").test
+            local etcd = require("apisix.core.etcd")
+            local code, body = t('/apisix/admin/protos/1',
+                 ngx.HTTP_PUT,
+                 [[{
+                    "content" : "syntax = \"proto3\";
+                      package helloworld;
+                      service Greeter {
+                          rpc SayHello (HelloRequest) returns (HelloReply) {}
+                      }
+                      message HelloRequest {
+                          string name = 1;
+                      }
+                      message HelloReply {
+                          string message = 1;
+                      }"
+                   }]]
+                )
+
+            if code >= 300 then
+                ngx.status = code
+            end
+            ngx.say(body)
+        }
+    }
+--- request
+GET /t
+--- response_body
+passed
+
+
+
+=== TEST 3: set routes(id: 2)
+--- config
+    location /t {
+        content_by_lua_block {
+            local t = require("lib.test_admin").test
+            local code, body = t('/apisix/admin/routes/2',
+                ngx.HTTP_PUT,
+                [[{
+                    "methods": ["GET", "POST"],
+                    "uri": "/grpctest",
+                    "plugins": {
+                        "grpc-transcode": {
+                            "proto_id": "1",
+                            "service": "helloworld.Greeter",
+                            "method": "SayHello"
+                        }
+                    },
+                    "upstream": {
+                        "scheme": "grpc",
+                        "type": "roundrobin",
+                        "nodes": {
+                            "127.0.0.1:50051": 1
+                        }
+                    }
+                }]]
+            )
+
+            if code >= 300 then
+                ngx.status = code
+            end
+            ngx.say(body)
+        }
+    }
+--- request
+GET /t
+--- response_body
+passed
+
+
+
+=== TEST 4: hit route
+--- request
+GET /grpctest?name=world
+--- response_body eval
+qr/\{"message":"Hello world"\}/
+
+
+
+=== TEST 5: successful batch-requests for both grpc and http
+--- config
+    location = /aggregate {
+        content_by_lua_block {
+            local core = require("apisix.core")
+            local t = require("lib.test_admin").test
+            local code, body = t('/apisix/batch-requests',
+                 ngx.HTTP_POST,
+                 [=[{
+                    "headers": {
+                        "Content-Type":"application/json"
+                    },
+                    "pipeline":[
+                        {
+                            "method":"GET",
+                            "path":"/grpctest"
+                        },
+                        {
+                            "method":"GET",
+                            "path":"/get"
+                        }
+                    ]
+                }]=],
+                [=[[
+                {
+                    "status": 200,
+                    "body":"{\"message\":\"Hello \"}"
+                },
+                {
+                    "status": 200,
+                    "body":"hello"
+                }
+                ]]=])
+
+            ngx.status = code
+            ngx.say(body)
+        }
+    }
+
+    location = /get {
+        content_by_lua_block {
+            ngx.print("hello")
+        }
+    }
+--- request
+GET /aggregate
+--- response_body
+passed