feat: add http interface to get a specified config

include/dsn/utility/flags.h

@@ -118,4 +118,7 @@ extern bool has_tag(const std::string &name, const flag_tag &tag);
 
 // list all the flags
 extern std::string list_all_flags();
+
+// get the json string of a specified flag
+extern error_with<std::string> get_flag_str(const std::string &flag_name);
 } // namespace dsn

src/http/builtin_http_calls.cpp

@@ -78,6 +78,10 @@ namespace dsn {
             [](const http_request &req, http_response &resp) { update_config(req, resp); })
         .with_help("Updates the value of a config");
 
+    register_http_call("config")
+        .with_callback([](const http_request &req, http_response &resp) { get_config(req, resp); })
+        .with_help("get the value of a config");
+
     register_http_call("configs")
         .with_callback(
             [](const http_request &req, http_response &resp) { list_all_configs(req, resp); })

src/http/builtin_http_calls.h

@@ -36,4 +36,5 @@ extern void update_config(const http_request &req, http_response &resp);
 
 extern void list_all_configs(const http_request &req, http_response &resp);
 
+extern void get_config(const http_request &req, http_response &resp);
 } // namespace dsn

src/http/config_http_service.cpp

@@ -48,4 +48,25 @@ void list_all_configs(const http_request &req, http_response &resp)
     resp.body = list_all_flags();
     resp.status_code = http_status_code::ok;
 }
+
+void get_config(const http_request &req, http_response &resp)
+{
+    std::string config_name;
+    for (const auto &p : req.query_args) {
+        if ("name" == p.first) {
+            config_name = p.second;
+        } else {
+            resp.status_code = http_status_code::bad_request;
+            return;
+        }
+    }
+
+    auto res = get_flag_str(config_name);
+    if (res.is_ok()) {
+        resp.body = res.get_value();
+    } else {
+        resp.body = res.get_error().description();
+    }
+    resp.status_code = http_status_code::ok;
+}
 } // namespace dsn

src/utils/flags.cpp

@@ -215,6 +215,16 @@ class flag_registry : public utils::singleton<flag_registry>
         return it->second.has_tag(tag);
     }
 
+    error_with<std::string> get_flag_str(const std::string &name) const
+    {
+        const auto iter = _flags.find(name);
+        if (iter == _flags.end()) {
+            return error_s::make(ERR_OBJECT_NOT_FOUND, fmt::format("{} is not found", name));
+        }
+
+        return iter->second.to_json();
+    }
+
     std::string list_all_flags() const
     {
         utils::table_printer tp;
@@ -272,6 +282,11 @@ flag_tagger::flag_tagger(const char *name, const flag_tag &tag)
     return flag_registry::instance().has_tag(name, tag);
 }
 
+/*extern*/ error_with<std::string> get_flag_str(const std::string &flag_name)
+{
+    return flag_registry::instance().get_flag_str(flag_name);
+}
+
 /*extern*/ std::string list_all_flags() { return flag_registry::instance().list_all_flags(); }
 
 } // namespace dsn