fix: standby meta server exits abnormally with core dump after receiving the http request /meta/cluster

cmake_modules/BaseFunctions.cmake

@@ -205,6 +205,10 @@ function(dsn_setup_compiler_flags)
   # We want access to the PRI* print format macros.
   add_definitions(-D__STDC_FORMAT_MACROS)
 
+  if(${BUILD_TEST})
+    add_definitions(-DMOCK_TEST)
+  endif()
+
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++17 -gdwarf-4" CACHE STRING "" FORCE)
 
   #  -Wall: Enable all warnings.

src/meta/CMakeLists.txt

@@ -57,8 +57,6 @@ set(MY_BOOST_LIBS Boost::system Boost::filesystem)
 # Extra files that will be installed
 set(MY_BINPLACES "")
 
-add_definitions(-DDSN_MOCK_TEST)
-
 dsn_add_shared_library()
 
 add_subdirectory(test)

src/meta/meta_http_service.cpp

@@ -460,8 +460,9 @@ void meta_http_service::list_node_handler(const http_request &req, http_response
 
 void meta_http_service::get_cluster_info_handler(const http_request &req, http_response &resp)
 {
-    if (!redirect_if_not_primary(req, resp))
+    if (!redirect_if_not_primary(req, resp)) {
         return;
+    }
 
     dsn::utils::table_printer tp;
     std::ostringstream out;
@@ -827,12 +828,29 @@ void meta_http_service::update_scenario_handler(const http_request &req, http_re
 
 bool meta_http_service::redirect_if_not_primary(const http_request &req, http_response &resp)
 {
-#ifdef DSN_MOCK_TEST
-    return true;
+#ifdef MOCK_TEST
+    // To enable MOCK_TEST, the option BUILD_TEST for cmake should be opened by:
+    //     cmake -DBUILD_TEST=ON ...
+    // which could be done by building Pegasus with tests by:
+    //     ./run.sh build --test ...
+    //
+    // If `_service->_balancer` is not null, it must has been initialized by mocking, in which case
+    // just returning true is ok.
+    //
+    // Otherwise, once `_service->_balancer` is null, which means this must be a standby meta
+    // server, returning true would lead to coredump due to null `_service->_balancer` while
+    // processing requests in `get_cluster_info_handler`. Thus it should go through the following
+    // normal process instead of just returning true.
+    if (_service->_balancer) {
+        return true;
+    }
 #endif
+
     rpc_address leader;
-    if (_service->_failure_detector->get_leader(&leader))
+    if (_service->_failure_detector->get_leader(&leader)) {
         return true;
+    }
+
     // set redirect response
     resp.location = "http://" + leader.to_std_string() + '/' + req.path;
     if (!req.query_args.empty()) {

src/utils/api_utilities.h

@@ -98,7 +98,7 @@ extern void dsn_coredump();
         }                                                                                          \
     } while (0)
 
-#ifdef DSN_MOCK_TEST
+#ifdef MOCK_TEST
 #define mock_private public
 #define mock_virtual virtual
 #else

src/utils/metrics.h

@@ -1404,7 +1404,7 @@ class percentile : public closeable_metric
             _full_nth_elements[i].store(value_type{}, std::memory_order_relaxed);
         }
 
-#ifdef DSN_MOCK_TEST
+#ifdef MOCK_TEST
         if (interval_ms == 0) {
             // Timer is disabled.
             return;