feat(interactive): Support stopping query service

docs/flex/interactive/development/admin_service.md

@@ -21,7 +21,8 @@ The table below provides an overview of the available APIs:
 | GetProcedure    | GET /v1/graph/{graph}/procedure/{proc_name} | Get the metadata of the procedure.                                 |
 | DeleteProcedure | DELETE /v1/graph/{graph}/procedure/{proc_name} | Delete the specified procedure.                                   |
 | UpdateProcedure | PUT /v1/graph/{graph}/procedure/{proc_name} | Update some metadata for the specified procedure, i.e. update description, enable/disable. |
-| StartService   | POST /v1/service/start                     | Start the service on the graph specified in request body.          |
+| StartService   | POST /v1/service/start                     | Start the query service on the graph specified in request body.          |
+| StopService    | GET /v1/service/stop                     | Stop the query service                                            |
 | ServiceStatus  | GET /v1/service/status                    | Get current service status.                                        |
 | SystemMetrics     | GET /v1/node/status                       | Get the system metrics of current host/pod, i.e. CPU usage, memory usages.                    |
 
@@ -986,6 +987,35 @@ curl -X POST -H "Content-Type: application/json" "http://[host]/v1/service/start
 - `200 OK`: Request successful.
 - `500 Internal Error`: Server internal Error.
 
+### StopService (ServiceManagement Category)
+
+#### Description 
+
+Stop the current running query service. 
+
+#### HTTP Request
+- **Method**: POST
+- **Endpoint**: `/v1/service/stop`
+- **Content-type**: `application/json`
+
+#### Curl Command Example
+```bash
+curl -X POST -H "Content-Type: application/json" "http://[host]/v1/service/stop"
+```
+
+#### Expected Response
+- **Format**: application/json
+- **Body**:
+```json
+{
+  "message": "message"
+}
+```
+
+#### Status Codes
+- `200 OK`: Request successful.
+- `500 Internal Error`: Server internal Error.
+
 ### ServiceStatus
 
 #### Description

flex/engines/http_server/actor/admin_actor.act.cc

@@ -349,12 +349,40 @@ seastar::future<query_result> admin_actor::start_service(
     }
     hqps_service.start_query_actors();  // start on a new scope.
     LOG(INFO) << "Successfully restart query actors";
+    // now start the compiler
+    auto schema_path =
+        server::WorkDirManipulator::GetGraphSchemaPath(graph_name);
+    if (!hqps_service.start_compiler_subprocess(schema_path)) {
+      LOG(ERROR) << "Fail to start compiler";
+      return seastar::make_exception_future<query_result>(
+          seastar::sstring("Fail to start compiler"));
+    }
     LOG(INFO) << "Successfully started service with graph: " << graph_name;
     return seastar::make_ready_future<query_result>(
         "Successfully start service");
   });
 }
 
+// Stop service.
+// Actually stop the query_handler's actors.
+// The port is still connectable.
+seastar::future<query_result> admin_actor::stop_service(
+    query_param&& query_param) {
+  auto& hqps_service = HQPSService::get();
+  return hqps_service.stop_query_actors().then([&hqps_service] {
+    LOG(INFO) << "Successfully stopped query handler";
+    if (hqps_service.stop_compiler_subprocess()) {
+      LOG(INFO) << "Successfully stop compiler";
+      return seastar::make_ready_future<query_result>(
+          seastar::sstring("Successfully stop service"));
+    } else {
+      LOG(ERROR) << "Fail to stop compiler";
+      return seastar::make_ready_future<query_result>(
+          seastar::sstring("Fail to stop compiler"));
+    }
+  });
+}
+
 // get service status
 seastar::future<query_result> admin_actor::service_status(
     query_param&& query_param) {

flex/engines/http_server/actor/admin_actor.act.h

@@ -43,6 +43,8 @@ class ANNOTATION(actor:impl) admin_actor : public hiactor::actor {
 
   seastar::future<query_result> ANNOTATION(actor:method) start_service(query_param&& param);
 
+  seastar::future<query_result> ANNOTATION(actor:method) stop_service(query_param&& param);
+
   seastar::future<query_result> ANNOTATION(actor:method) service_status(query_param&& param);
 
   seastar::future<query_result> ANNOTATION(actor:method) get_procedure_by_procedure_name(procedure_query_param&& param);

flex/engines/http_server/handler/admin_http_handler.cc

@@ -409,9 +409,21 @@ class admin_http_service_handler_impl : public seastar::httpd::handler_base {
                   std::unique_ptr<seastar::httpd::reply>>(std::move(rep));
             });
       } else if (action == "stop") {
-        return seastar::make_exception_future<
-            std::unique_ptr<seastar::httpd::reply>>(
-            std::runtime_error("Stopping service not supported."));
+        return admin_actor_refs_[dst_executor]
+            .stop_service(query_param{std::move(req->content)})
+            .then_wrapped([rep = std::move(rep)](
+                              seastar::future<query_result>&& fut) mutable {
+              if (__builtin_expect(fut.failed(), false)) {
+                return seastar::make_exception_future<
+                    std::unique_ptr<seastar::httpd::reply>>(
+                    fut.get_exception());
+              }
+              auto result = fut.get0();
+              rep->write_body("application/json", std::move(result.content));
+              rep->done();
+              return seastar::make_ready_future<
+                  std::unique_ptr<seastar::httpd::reply>>(std::move(rep));
+            });
       } else {
         return seastar::make_exception_future<
             std::unique_ptr<seastar::httpd::reply>>(